Ethylene in Plant Biology E-Book
147,99 €
Mehr erfahren.
- Herausgeber: John Wiley & Sons
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
ETHYLENE IN PLANT BIOLOGY Comprehensive resource detailing the role of ethylene in plant development regulation, gene regulation, root development, stress tolerance, and more Ethylene in Plant Biology presents ethylene research from leading laboratories around the globe to allow readers to gain strong foundational coverage of the topic and aid in further ethylene research as it pertains to plant biology. The work covers general ideas as well as more specific and technical knowledge, detailing the overall role of ethylene in plant biology as a gaseous plant hormone that has emerged as an important signaling molecule which regulates several steps of a plant's life cycle. The ideas covered in the work range from discovery of ethylene, to its wide roles in plant growth and development, all the way to niche topics such as stress acclimation. Written by highly qualified authors in fields directly related to plant biology and research, the work is divided into 20 chapters, with each chapter covering a specific facet of ethylene or the interaction between ethylene and plant health. Topics discussed in the text include: * Our current understanding of ethylene and fruit ripening, plus the role of ethylene in flower and fruit development * Ethylene implications in root development and crosstalk of ethylene with other phytohormones in plant development * Ethylene as a multitasking regulator of abscission processes and powerful coordinator of drought responses * Mechanisms for ethylene synthesis and homeostasis in plants, along with ethylene and phytohormone crosstalk in plant defense * Ethylene and metabolic reprogramming under abiotic stresses, as well as ethylene's applications in crop improvement For biologists, scientists, researchers, and policy makers in the agriculture and pharmaceutical industries, Ethylene in Plant Biology is a key resource to understand the state of the art in the field and establish a foundation of knowledge that can power future research efforts and practical applications.
Sie lesen das E-Book in den Legimi-Apps auf:
Seitenzahl: 1107
Veröffentlichungsjahr: 2022
Ähnliche
Table of Contents
Cover
Title Page
Copyright Page
List of Contributors
Preface
1 Ethylene Implication in Root Development
1.1 Ethylene and Its Role in Overall Plant Development
1.2 Ethylene Response Pathway in Plants
1.3 Root Development in Plants
1.4 Ethylene‐Mediated Regulation of Root Development
1.5 Conclusions and Future Perspectives
References
2 Crosstalk of Ethylene and Other Phytohormones in the Regulation of Plant Development
2.1 Introduction
2.2 Ethylene in the Regulation of Plant Development
2.3 Ethylene Crosstalk with Other Hormones During Plant Development
2.4 Conclusion
References
3 Ethylene and Regulation of Metabolites in Plants
3.1 Introduction
3.2 Importance of Metabolites in Plants
3.3 Influence of Ethylene on the Regulation of Plant Metabolites
3.4 Conclusion
References
4 Ethylene as a Multitasking Regulator of Abscission Processes
4.1 Introduction
4.2 Ethylene as a Signal for Separation in Abscising Organs
4.3 Ethylene Function in the Abscission Zone
4.4 Ethylene and Hormonal Co‐Workers
4.5 Conclusions and Future Perspectives
References
5 Ethylene:
5.1 Drought as a Limiting Factor for Plant Growth and Development
5.2 Roots First Encounters Drought Stress
5.3 The Response of Aboveground Parts to Water Deficits in Soil
5.4 The
ET
‐Dependent Mechanism that Plants Utilize to Cope with the Effects of Drought
5.5 Ethylene Interactions with Other Hormones in Drought Responses
5.6 Conclusions and Future Prospects
References
6 Current Understanding of Ethylene and Fruit Ripening
6.1 Introduction
6.2 Ethylene and Fruit Ripening
6.3 Ethylene Biosynthesis in Fruits
6.4 Ethylene Perception and Signaling
6.5 Altered Ethylene Perception Impairs Fruit Ripening
6.6 Transcriptional and Epigenetic Regulation of Fruit Ripening
6.7 Ripening‐Related Promoters
6.8 Genetic Manipulation of Fruit Ripening
6.9 Conclusions
Acknowledgements
References
7 Ethylene and ROS Crosstalk in Plant Developmental Processes
7.1 Introduction
7.2 ET Releases Seeds, Breaks Bud Dormancy, and Promotes Germination
7.3 Ethylene Regulates Cell Division and Cell Elongation
7.4 Ethylene and Apical Hook Development
7.5 Ethylene and Hypocotyl Growth
7.6 Ethylene and Root Growth Development
7.7 Ethylene in Leaf Growth and Development
7.8 Ethylene Induces Epinasty and Hyponasty
7.9 Ethylene and Flower Development
7.10 Ethylene Promotes the Ripening of Some Fruits
7.11 Ethylene Promotes Leaf, Flower, and Fruit Abscission
7.12 Ethylene Induces Senescence
7.13 Ethylene and Cell Death
7.14 Concluding Remarks and Perspectives
References
8 Role of Ethylene in Flower and Fruit Development
8.1 Introduction
8.2 Involvement of Ethylene in the Control of the Flowering Transition
8.3 Involvement of Ethylene in Flower Development
8.4 Involvement of Ethylene in Sex Determination and Unisexual Flower Development
8.5 Involvement of Ethylene in Fruit Development
References
9 Ethylene and Nutrient Regulation in Plants
9.1 Introduction
9.2 Biosynthesis and Signaling of Ethylene
9.3 Availability of Mineral Nutrients in Plants
9.4 Ethylene and Regulation of Mineral Nutrients in Plants
9.5 Conclusion and Future Prospects
References
10 Plant Metabolism Adjustment in Exogenously Applied Ethylene under Stress
10.1 Introduction
10.2 Phytohormones and Stress
10.3 Ethylene
10.4 Ethylene and Stress
10.5 Concluding Remarks
References
11 Role of ET and ROS in Salt Homeostasis and Salinity Stress Tolerance and Transgenic Approaches to Making Salt‐Tolerant Crops
11.1 Introduction
11.2 Discussion
References
12 Ethylene and Phytohormone Crosstalk in Plant Defense Against Abiotic Stress
12.1 Introduction
12.2 Ethylene Biosynthesis and Signaling Pathways
12.3 Role of Plant Hormones in Plant Stress Responses
12.4 Plant Hormones Crosstalk with Ethylene in Plant Defense against Abiotic Stress
12.5 Conclusion and Future Directions
References
13 Mechanism for Ethylene Synthesis and Homeostasis in Plants
13.1 Introduction
13.2 Mechanism of Ethylene Hormone Biosynthesis
13.3 Regulation of the Ethylene Synthesis Pathway
13.4 Ethylene Hormone Homeostasis: Current Updates
13.5 Ethylene's Importance in Biotic and Abiotic Homeostasis
13.6 ROS Scavenging Mechanisms Through Ethylene Regulation
13.7 ET Crosstalk
13.8 Conclusion
References
14 Ethylene and Nitric Oxide Under Salt Stress:
14.1 Introduction
14.2 Mediation of Salt Tolerance by Ethylene and Nitric Oxide
14.3 Regulatory Interactions Between Ethylene and NO for Salt Tolerance
14.4 Conclusions
Acknowledgment
References
15 Ethylene and Metabolic Reprogrammingunder Abiotic Stresses
15.1 Introduction
15.2 Abiotic Stresses Change Gene Expression Patterns
15.3 Ethylene's Role in Various Abiotic Stresses
15.4 Conclusion
References
16 Regulation of Thermotolerance Stress in Crops by Plant Growth‐Promoting Rhizobacteria Through Ethylene Homeostasis
16.1 Introduction
16.2 Synthesis of Ethylene in Plant Roots and Rhizobial Inoculation
16.3 Basal and Acquired Thermotolerance
16.4 Hormone Involvement in Heat Stress
16.5 PGPR Influenced Ethylene Homeostasis
16.6 Conclusion
Acknowledgments
References
17 Ethylene
17.1 Introduction to Ethylene
17.2 Functions of Ethylene
17.3 Ethylene and Signal Transduction
17.4 Role of Ethylene Response Factors (ERFs) in Fruit Ripening
17.5 Ethylene Crosstalk During Ripening
17.6 Regulating Ethylene Signal Transduction for Agricultural and Horticultural Uses
17.7 Gene‐ and Genomics‐Related Approach
17.8 Altering Ethylene Levels in Plants
17.9 Inhibition of Fruit Ripening
17.10 Conclusion
References
18 Role of Ethylene in Combating Biotic Stress
18.1 Introduction
18.2 Biotic Stress in Plants
18.3 Ethylene Biosynthesis in Response to Stress
18.4 Role of Ethylene in Reducing ROS Accumulation under Biotic Stress
18.5 Role of Ethylene in Crop Yield under Biotic Stress
18.6 Conclusion
References
19 Ethylene and Nitric Oxide Crosstalk in Plants under Abiotic Stress
19.1 Introduction
19.2 Ethylene (ET): A Key Regulatory Molecule in Plants
19.3 Crosstalk with Other Plant Hormones
19.4 Role of Nitric Oxide (NO) in Plants
19.5 NO Crosstalk with Plant Hormones
19.6 ET and NO Crosstalk under Abiotic Stress
19.7 Conclusions and Future Perspectives
References
20 Polyamine Metabolism and Ethylene Signaling in Plants
20.1 Introduction
20.2 PA Metabolism (Polyamine Biosynthesis and Polyamine Catabolism)
20.3 ET Biosynthesis, Perception, and Signal Transduction
20.4 Molecular and Biochemical Aspects of ET Signaling
References
Index
End User License Agreement
List of Tables
Chapter 8
Table 8.1 Role of ethylene in flowering transition and flower and fruit dev...
Table 8.2 Ethylene‐related genes involved in sex determination in different...
Chapter 10
Table 10.1 Effect of exogenous ethylene supplementation on plant metabolic ...
Chapter 11
Table 11.1 Summary of some transgenes involved in ion homeostasis for devel...
Table 11.2 Summary of some transgenes involved in ROS homeostasis for devel...
Table 11.3 Summary of some transgenes involved in ET biosynthesis metabolis...
Chapter 13
Table 13.1 Ethylene involvement in various plant functions.
Chapter 14
Table 14.1 Activation of different components of defense pathways in respon...
Table 14.2 Some literature on ethylene and NO interaction under salt stress...
Chapter 15
Table 15.1 ERF superfamily in crop species.
Table 15.2 ERF superfamily expression in plants under abiotic stress condit...
Chapter 16
Table 16.1 Gene influence in plants in response to abiotic stresses.
Chapter 18
Table 18.1 Ethylene‐related mutant or transgenic plants with altered ethyle...
List of Illustrations
Chapter 1
Figure 1.1 Ethylene biosynthesis and signaling pathway in
Arabidopsis
. When ...
Figure 1.2 Role of ethylene in the regulation of the root system architectur...
Chapter 2
Figure 2.1 Diagrammatic representation of the role of ethylene in regulating...
Figure 2.2 Diagram showing crosstalk between phytohormones in the regulation...
Chapter 3
Figure 3.1 Diagrammatic representation of the role of primary and secondary ...
Chapter 4
Figure 4.1 A model describing ET involvement in the subsequent stages of org...
Chapter 5
Figure 5.1 Model of drought‐triggered events related to ethylene biosynthesi...
Chapter 6
Figure 6.1 Diagrammatic representation of ethylene biosynthesis and ethylene...
Chapter 8
Figure 8.1 Floral transition models in different plant species. (a) The tran...
Figure 8.2 Ethylene mediates floral organ senescence and abscission and frui...
Figure 8.3 Sexual morphotypes observed in cucurbits. Schematic representatio...
Figure 8.4 A model outlining the interactions of major genes in the control ...
Chapter 9
Figure 9.1 Schematic representation showing ethylene biosynthesis and signal...
Chapter 10
Figure 10.1 A simplified representation of the deleterious effects of stress...
Chapter 12
Figure 12.1 A model of the ethylene biosynthesis pathway.
Figure 12.2 Diagrammatic representation of the ethylene signaling cascade....
Chapter 13
Figure 13.1 Mechanism of ethylene synthesis.
Figure 13.2 Structural changes occurred during ethylene synthesis.
Figure 13.3 Ethylene synthesis through the salvage pathway.
Figure 13.4 Ethylene regulation.
Chapter 15
Figure 15.1 Effects of abiotic stress on plants.
Figure 15.2 Plant responses to stress through signal transduction.
Figure 15.3 ROS production to increase stress tolerance by increasing ethyle...
Chapter 17
Figure 17.1 Ethylene signaling in plants.
Figure 17.2 Modulation of fruits using different techniques affects the comm...
Figure 17.3 Fruit ripening procedure modification using various approaches b...
Chapter 18
Figure 18.1 Interaction of ethylene and jasmonic acid signaling in response ...
Chapter 19
Figure 19.1 Ethylene biosynthesis and its regulation in plants under stress ...
Figure 19.2 Possible sources of nitric oxide in plants.
Figure 19.3 Schematic demonstration of ethylene (ET)‐nitric oxide (NO) inter...
Chapter 20
Figure 20.1 An overview of polyamine metabolism and ethylene biosynthesis.
Figure 20.2 A model of the ET signaling pathway.
Guide
Cover Page
Title Page
Copyright Page
List of Contributors
Preface
Table of Contents
Begin Reading
Index
WILEY END USER LICENSE AGREEMENT
Pages
i
ii
v
vi
vii
viii
ix
x
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
Ethylene in Plant Biology
Edited by
Samiksha Singh
Banaras Hindu University
Varanasi, India
Tajammul Husain
University of Allahabad
Prayagraj, India
Vijay Pratap Singh
C.M.P. Degree College
Prayagraj, India
Durgesh Kumar Tripathi
Amity University Uttar Pradesh
Noida, India
Sheo Mohan Prasad
University of Allahabad
Prayagraj, India
Nawal Kishore Dubey
Banaras Hindu University
Varanasi, India
This edition first published 2023© 2023 John Wiley & Sons Ltd
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by law. Advice on how to obtain permission to reuse material from this title is available at http://www.wiley.com/go/permissions.
The right of Samiksha Singh, Tajammul Husain, Vijay Pratap Singh, Durgesh Kumar Tripathi, Sheo Mohan Prasad, and Nawal Kishore Dubey to be identified as the authors of the editorial material in this work has been asserted in accordance with law.
Registered OfficesJohn Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USAJohn Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK
Editorial OfficeThe Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK
For details of our global editorial offices, customer services, and more information about Wiley products visit us at www.wiley.com.
Wiley also publishes its books in a variety of electronic formats and by print‐on‐demand. Some content that appears in standard print versions of this book may not be available in other formats.
Limit of Liability/Disclaimer of WarrantyThe contents of this work are intended to further general scientific research, understanding, and discussion only and are not intended and should not be relied upon as recommending or promoting scientific method, diagnosis, or treatment by physicians for any particular patient. In view of ongoing research, equipment modifications, changes in governmental regulations, and the constant flow of information relating to the use of medicines, equipment, and devices, the reader is urged to review and evaluate the information provided in the package insert or instructions for each medicine, equipment, or device for, among other things, any changes in the instructions or indication of usage and for added warnings and precautions. While the publisher and authors have used their best efforts in preparing this work, they make no representations or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties, including without limitation any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives, written sales materials or promotional statements for this work. The fact that an organization, website, or product is referred to in this work as a citation and/or potential source of further information does not mean that the publisher and authors endorse the information or services the organization, website, or product may provide or recommendations it may make. This work is sold with the understanding that the publisher is not engaged in rendering professional services. The advice and strategies contained herein may not be suitable for your situation. You should consult with a specialist where appropriate. Further, readers should be aware that websites listed in this work may have changed or disappeared between when this work was written and when it is read. Neither the publisher nor authors shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages.
Library of Congress Cataloging‐in‐Publication Data
Name: Singh, Samiksha, 1985– editor.Title: Ethylene in plant biology / edited by Samiksha Singh, Banaras Hindu University, Varanasi, India, Tajammul Husain, University of Allahabad,Prayagraj, India, Vijay Pratap Singh, C.M.P. Degree College, Prayagraj, India, Durgesh Kumar Tripathi, Amity University Uttar Pradesh, Noida, India, Sheo Mohan Prasad, University of Allahabad, Prayagraj, India, Nawal Kishore Dubey, Banaras Hindu University, Varanasi, India.Description: First edition. | Hoboken, NJ : Wiley, 2023. | Includes bibliographical references and index.Identifiers: LCCN 2022017470 (print) | LCCN 2022017471 (ebook) | ISBN 9781119744689 (cloth) | ISBN 9781119744696 (adobe pdf) | ISBN 9781119744702 (epub)Subjects: LCSH: Plants–Effect of ethylene on.Classification: LCC QK753.E8 E85 2022 (print) | LCC QK753.E8 (ebook) | DDC 581.3–dc23/eng/20220528LC record available at https://lccn.loc.gov/2022017470LC ebook record available at https://lccn.loc.gov/2022017471
Cover design: WileyCover image: © boonchai wedmakawand/Getty Image
List of Contributors
Nisha AgrawalSchool of Biochemistry, Devi Ahilya Vishwavidyalaya, Indore, Madhya Pradesh, India
Juan D. AlchéDepartment of Stress, Development and Signaling, Estación Experimental del Zaidín, Spanish National Research Council (CSIC), Granada, Spain
Nimisha AmistPlant Physiology Laboratory, Department of Botany, University of Allahabad, Prayagraj, Uttar Pradesh, India
Renu BhardwajDepartment of Botanical and Environmental Sciences, Guru Nanak Dev University, Amritsar, Punjab, India
Savita BhardwajDepartment of Botany, School of Bioengineering and Biosciences, Lovely Professional University, Phagwara, Punjab, India
Sebastian BurchardtDepartment of Plant Physiology and Biotechnology, Faculty of Biological and Veterinary Sciences, Nicolaus Copernicus University, Toruń, Poland
Kumar Chandra‐kuntalSchool of Life Sciences, Devi Ahilya Vishwavidyalaya, Indore, Madhya Pradesh, India
Anita DubeyMB Khalsa College, Indore, Madhya Pradesh, India
Neeraj Kumar DubeyBotany Department, Rashtriya Snatkottar Mahavidyalaya, Jamuhai, Jaunpur, Uttar Pradesh, India
Mehar FatmaPlant Physiology and Biochemistry Division, Department of Botany, Aligarh Muslim University, Aligarh, Uttar Pradesh, India
Víctor García‐GaytánEl Colegio de Michoacán, A.C. LADIPA, La Piedad, Jardines del Cerro Grande, México
Alicia GarcíaDepartamento de Biología y Geología, Research Center CIAIMBITAL and Agrifood Campus of International Excellence CeiA3, University of Almería, Almería, Spain
Harsha GautamPlant Physiology and Biochemistry Division, Department of Botany, Aligarh Muslim University, Aligarh, Uttar Pradesh, India
Parishmita GogoiBiological Science & Technology Division, CSIR‐North East Institute of Science and Technology, Jorhat, Assam, India
Priyanka GogoiBiological Science & Technology Division, CSIR‐North East Institute of Science and Technology, Jorhat, Assam, India
Aditi GuptaCSIR‐National Botanical Research Institute (NBRI), Lucknow, India
Arvind GuptaDepartment of Biotechnology, Hemvati Nandan Bahuguna Garhwal (Central) University, Srinagar Garhwal, Uttarakhand, India
Kapil GuptaDepartment of Plant Biotechnology, CSIR‐Central Institute of Medicinal and Aromatic Plants, Lucknow, Uttar PradeshandDepartment of Biotechnology, Siddharth University, Kapilvastu, Uttar Pradesh, India
Shubhra GuptaDepartment of Biotechnology, Central University of Rajasthan, Ajmer, Rajasthan, India
Noushina IqbalDepartment of Botany, Jamia Hamdard University, New Delhi, India
Badar JahanPlant Physiology and Biochemistry Division, Department of Botany, Aligarh Muslim University, Aligarh, Uttar Pradesh, India
Meeta JainSchool of Biochemistry, Devi Ahilya University, Indore, Madhya Pradesh, India
Manuel JamilenaDepartamento de Biología y Geología, Research Center CIAIMBITAL and Agrifood Campus of International Excellence CeiA3, University of Almería, Almería, Spain
Sadaf JanDepartment of Biotechnology, School of Bioengineering and Biosciences, Lovely Professional University, Phagwara, Punjab, India
Raman JasrotiaDepartment of Zoology, University of Jammu, Jammu and Kashmir, India
Shivam JasrotiaDepartment of Zoology, GovtDegree College Basohli, Jammu and Kashmir, India
Kanchan JumraniDivision of Plant Physiology, Indian Institute of Soybean Research, Indore, Madhya Pradesh, India
Dhriti KapoorDepartment of Botany, School of Bioengineering and Biosciences, Lovely Professional University, Phagwara, Punjab, India
Jacek KarwaszewskiDepartment of Plant Physiology and Biotechnology, Faculty of Biological and Veterinary Sciences, Nicolaus Copernicus University, Toruń, Poland
Sunita KatariaSchool of Biochemistry, Devi Ahilya University, Indore, Madhya Pradesh, India
Ekhlaque A. KhanDepartment of Biotechnology, Chaudhary Bansi Lal University, Bhiwani, Haryana, India
Nafees A. KhanPlant Physiology and Biochemistry Division, Department of Botany, Aligarh Muslim University, Aligarh, Uttar Pradesh, India
Shubhra KharePlant Physiology Laboratory, Department of Botany, University of Allahabad, Prayagraj, Uttar Pradesh, India
Jasminkumar KheniDepartment of Biotechnology, Junagadh Agricultural University, Junagadh, Gujarat, India
Agata KućkoDepartment of Plant Physiology, Institute of Biology, Warsaw University of Life Sciences‐SGGW, Warsaw, Poland
Pragati KumariDepartment of Botany and Microbiology, Hemvati Nandan Bahuguna Garhwal (Central) University, Srinagar Garhwal, Uttarakhand, India
Cecilia MartínezDepartamento de Biología y Geología, Research Center CIAIMBITAL and Agrifood Campus of International Excellence CeiA3, University of Almería, Almería, Spain
Asim MasoodPlant Physiology and Biochemistry Division, Department of Botany, Aligarh Muslim University, Aligarh, Uttar Pradesh, India
NiharikaPlant Physiology Laboratory, Department of Botany, University of Allahabad, Prayagraj, Uttar Pradesh, India
Satendra Pal SinghDepartment of Botany, Y.D. (P.G.) College, Lakhimpur Kheri, Uttar Pradesh, India
Juhie Joshi‐PaneriPlant Science Department, McGill University, Montreal, Canada
Jogeswar PanigrahiDepartment of Biosciences and Bioinformatics, Khallikote University, Berhampur, Odisha, India
Surendra Pratap SinghDepartment of Botany, D.A.V. College, C.S.J.M. University, Kanpur, Uttar Pradesh, India
Anshu RastogiLaboratory of Bioclimatology, Department of Ecology and Environmental Protection, Poznan University of Life Sciences, Poznan, Poland
Peer SaffeullahDepartment of Botany, Jamia Hamdard, New Delhi, India
Zebus SeharPlant Physiology and Biochemistry Division, Department of Botany, Aligarh Muslim University, Aligarh, Uttar Pradesh, India
Dhriti SharmaDepartment of Botany, School of Bioengineering and Biosciences, Lovely Professional University, Phagwara, Punjab, India
Ratul SaikiaBiological Science & Technology Division, CSIR‐North East Institute of Science and Technology, Jorhat, Assam, India
Ajey SinghNehru Gram Bharti (Deemed toBe University), Prayagraj, Uttar Pradesh, India
Manjul SinghCentre for Research in Agricultural Genomics (CRAG), CSIC‐IRTA‐UAB‐UB, Barcelona, Spain
N.B. SinghPlant Physiology Laboratory, Department of Botany, University of Allahabad, Prayagraj, Uttar Pradesh, India
Rattandeep SinghDepartment of Biotechnology, School of Bioengineering and Biosciences, Lovely Professional University, Phagwara, Punjab, India
Zahra SouriLaboratory of Plant Physiology, Department of Biology, Faculty of Science, Razi University, Kermanshah, Iran
Archana ThakurUniversity Grants Commission, New Delhi, India
Rahul ThakurDepartment of Biotechnology, Hemvati Nandan Bahuguna Garhwal (Central) University, Srinagar Garhwal, Uttarakhand, India
Timothy J. TranbargerUMR DIADE, IRD Centre de Montpellier, Université de Montpellier, Institut de Recherche pour le Développement, Montpellier, France
Rachana TripathiSchool of Life Science, Devi Ahilya Vishwavidyalaya, Indore, Madhya Pradesh, India
Shahid UmarDepartment of Botany, Jamia Hamdard, New Delhi, India
Tunisha VermaDepartment of Botany, School of Bioengineering and Biosciences, Lovely Professional University, Phagwara, Punjab, India
Emilia WilmowiczDepartment of Plant Physiology and Biotechnology, Faculty of Biological and Veterinary Sciences, Nicolaus Copernicus University, Toruń, Poland
Archana YadavBiological Science & Technology Division, CSIR‐North East Institute of Science and Technology, Jorhat, Assam, India
Saurabh YadavDepartment of Biotechnology, Hemvati Nandan Bahuguna Garhwal (Central) University, Srinagar Garhwal, Uttarakhand, India
Preface
Ethylene, a gaseous plant hormone, has emerged as an important signaling molecule that regulates several steps of the plant life cycle. The development of plants requires complex signaling of various molecules like ethylene. Further, to restore and reestablish cellular homeostasis under stress conditions, regulation at the gene expression level takes place, which helps in achieving a proper phenological response.
In the recent past, various studies have demonstrated the role of ethylene in regulating seed germination, nodule formation, and nitrogen fixation, reactive oxygen species, and other plant hormonal signaling, and their subsequent impact on plant development under stress‐challenged and non‐stress‐challenged conditions. In recent years, various implications of ethylene have been reported on the growth and development of plants. Further, the roles of ethylene are emerging in plant developmental processes, and thus, research on the roles of ethylene in plant biology continues to increase. Moreover, research on the new roles of ethylene in plant biology is ongoing.
This edited book combines ethylene research from leading laboratories around the globe in one place to make it easily accessible to researchers, students, academics, etc. Twenty chapters have been compiled, and the topics covered range from the discovery of ethylene to its wide roles in plant growth and development and stress acclimation. Chapter 1 deals with the role of ethylene in root development. Chapter 2 presents the role of ethylene in plant development. Chapter 3 deals with the regulation of metabolites by ethylene. Chapter 4 deals with the regulatory role of ethylene in abscission processes. Chapter 5 presents the regulation of drought stress by ethylene. Chapter 6 discusses ethylene and fruit ripening. Chapter 7 deals with ethylene and reactive oxygen species crosstalk in plant development. Chapter 8 examines the role of ethylene in flower and fruit development. Chapter 9 deals with the role of ethylene in nutrient regulation in plants. Chapter 10 presents plant metabolism adjustments by ethylene under stress. Chapter 11 deals with the role of ethylene and reactive oxygen species in salinity stress tolerance and transgenic approaches to making salt‐tolerant crops. Chapter 12 presents ethylene and phytohormonal crosstalk in plant defense against abiotic stress. Chapter 13 describes the mechanism of ethylene synthesis and homeostasis in plants. Chapter 14 deals with ethylene and nitric oxide crosstalk under salt stress. Chapter 15 presents ethylene and metabolic reprogramming under abiotic stresses. Chapter 16 deals with the regulation of thermal stress in crops by plant growth‐promoting rhizobacteria through ethylene homeostasis. Chapter 17 discusses ethylene signaling, transgenics, and their applications in crop improvement. Chapter 18 presents the role of ethylene in combating biotic stress in plants. Chapter 19 deals with ethylene and nitric oxide crosstalk in plants under abiotic stress. Chapter 20 discusses polyamine metabolism and ethylene signaling in plants.
We believe that this book will serve as an important repository for students, academics, and researchers to understand various implications of ethylene in plants ranging from plant development to stress acclimation.
Samiksha SinghTajammul HusainVijay Pratap SinghDurgesh Kumar TripathiSheo Mohan PrasadNawal Kishore Dubey
1Ethylene Implication in Root Development
Aditi Gupta1, Anshu Rastogi2, and Manjul Singh3
1 CSIR-National Botanical Research Institute (NBRI), Lucknow, India
2 Laboratory of Bioclimatology, Department of Ecology and Environmental Protection, Poznan University of Life Sciences, Poznan, Poland
3 Centre for Research in Agricultural Genomics (CRAG), CSIC-IRTA-UAB-UB, Barcelona, Spain
1.1 Ethylene and Its Role in Overall Plant Development
Ethylene (or ethene, according to International Union of Pure and Applied Chemistry [IUPAC] nomenclature) is the simplest olefin gas biosynthesized by plants. Ethylene (ET) is the smallest phytohormone and one of the first gaseous hormones discovered around 100 years ago. It is widely known to regulate fruit ripening; however, the roles of the ET signaling pathway in regulating different aspects of plant development, growth, and stress responses have also been well‐studied in the last three decades (Dubois et al. 2018). ET functions as a hormone by performing cell‐to‐cell communication of signals in plants and can also act as a pheromone by diffusing to surrounding plants and inducing ET responses in them. As a signaling molecule, ET is able to regulate various developmental processes of plants such as seed germination, seedling development, root and shoot growth, fruit ripening, senescence, and abscission (Iqbal et al. 2017). It regulates root growth through a seemingly conserved pathway across monocot and dicot species. ET signals balance cell division and differentiation processes and can negatively affect tissue extension by interfering with cell elongation and proliferation. This balance between cell division, elongation, and differentiation events caused by ET and its interaction with other phytohormones, predominantly auxin, controls root system architecture (RSA) development. Besides the general growth and developmental regulatory functions, ET has a prominent role in plant responses to different stresses, such as salinity, flooding, cold, heavy metals, drought, etc. (Tao et al. 2015; Iqbal et al. 2017; Pan et al. 2019; Sytar et al. 2019; Wang and Huang 2019; Wang et al. 2020). This chapter summarizes the current knowledge about mechanisms of root development and root growth response via ET actions both independently and via signal crosstalk with other pathways.
1.2 Ethylene Response Pathway in Plants
ET is a small gaseous hormone that can freely diffuse across membranes and permits plant‐to‐plant communication. It is synthesized from methionine in three simple steps. The direct precursor of ET is 1‐aminocyclopropane‐1‐carboxylic acid (ACC). The rate‐limiting enzyme ACC‐synthases (ACS) catalyzes ACC to ET (Dubois et al. 2018) (Figure 1.1). ET homeostasis is maintained by transcriptional and post‐translational regulation of the ACS enzymes, as the ACS transcripts are responsive to different environmental factors such as water and light availability, and the enzyme can be phosphorylated and undergo protein degradation via mitogen‐activated protein kinase (MAPK) and ubiquitin‐mediated pathways, respectively (Dubois et al. 2018).
The ET signal transduction pathway has been extensively studied, and the components of the pathway were discovered mainly by studies performed with the model plant system Arabidopsis thaliana. The ET‐induced triple response in young seedlings was utilized to identify the components of the ET response pathway in plants through genetic screens. ETHYLENE RESISTANCE1 (ETR1) was the first ET receptor discovered through this approach (Bleecker et al. 1988). Further, a family of ET receptors was identified in the membrane of the endoplasmic reticulum, and Golgi bodies that include ETR2, ETHYLENE RESPONSE SENSOR1 (ERS1), ERS2, and ETHYLENE INSENSITIVE4 (EIN4) (Guo and Ecker 2004). ET signaling is essentially linear and includes a protein kinase CONSTITUTIVE TRIPLE RESPONSE 1 (CTR1), an ER‐localized transmembrane protein ETHYLENE‐INSENSITIVE 2 (EIN2), and downstream nuclear components such as EIN3, EIN3‐LIKE (EIL), and ETHYLENE RESPONSE FACTOR (ERF) transcription factors (Guo and Ecker 2004; Dubois et al. 2018) (Figure 1.1). The phytohormone receptors are primarily positive regulators, but in the case of ET, they act as negative regulators (Dubois et al. 2018). In the absence of ET, the receptors interact with and activate CTR1 (Lacey and Binder 2014). CTR1 then phosphorylates and represses EIN2. Two F‐box proteins, ETHYLENE INSENSITIVE2 TARGETING PROTEIN1 (ETP1) and ETP2, target phosphorylated EIN2 for 26S proteasomal degradation (Ju and Chang 2015). Upon ET perception, the receptor/CTR1 is targeted for 26S proteasome degradation (Shakeel et al. 2015) (Figure 1.1). In the presence of ET, when the repression of EIN2 is released, EIN2 is dephosphorylated; this dephosphorylation leads to its cleavage, thus releasing a C‐terminal fragment (EIN2‐C) that forms processing bodies or moves to the nucleus (Li et al. 2015; Merchante et al. 2015). The cleaved EIN2‐C binds to the 3′‐untranslated regions (3′‐UTRs) of ETHYLENE INSENSITIVE3 BINDING F‐BOX1 (EBF1) and EBF2, thereby repressing their turnover. EBF1 and EBF2 belong to F‐box proteins, which target the ET‐responsive TFs EIN3 and EIN3‐LIKE 1 (EIL1) for degradation (Guo and Ecker 2003; Potuschak et al. 2003). ET‐responsive TFs bind to ethylene‐responsive element (ERE) on the promoter of target genes to regulate transcription of many ET‐responsive genes and secondary TFs (Chang et al. 2013) (Figure 1.1). ET, through hierarchical events, regulates several developmental processes in plants by regulating gene expression differentially.
Although this canonical pathway is the predominant signaling cascade, alternative pathways also affect ET responses. Noncanonical pathway components such as RTE1 (REVERSION TO ETHYLENE SENSITIVITY1) and Auxin‐Regulated Gene involved in Organ Size (ARGOS) can negatively regulate the ET receptor and promote ET sensitivity (Resnick et al. 2006; Rai et al. 2015). There are multiple evidences of the interplay between specific ET receptor isoforms with the components of other phytohormone cascades such as Abscisic acid (ABA) and cytokinin. For instance, ETR1 and ETR2 are shown to be involved in ABA‐mediated control of seed germination in Arabidopsis (Yasumura et al. 2015; Bakshi et al. 2018). It was also demonstrated that ETR1 could physically interact with cytokinin receptor protein AHPs (Arabidopsis thaliana HISTIDINE PHOSPHOTRANSFER PROTEINS) and the ARRs (RESPONSE REGULATOR protein family in Arabidopsis) by its C‐terminal portion (Scharein et al. 2008; Scharein and Groth 2011; Zdarska et al. 2019). Both AHPs and ARRs can also control ET responses such as ET sensitivity, recovery upon ET removal, stomatal opening, and root apical meristem (RAM) development (Street et al. 2015; Binder et al. 2018; Zdarska et al. 2019). Finally, the transcriptional changes caused by cytokinin also showed considerable overlap with those controlled by ET (Nemhauser et al. 2006). EIN3 can also control transcriptional output by interacting with other transcription factors, depending on the growth conditions, such as PHYTOCHROME INTERACTING FACTOR 3 (PIF3) in the dark (Liu et al. 2017).
Figure 1.1 Ethylene biosynthesis and signaling pathway in Arabidopsis. When ethylene is absent, its receptors signal CTR1 to phosphorylate EIN2, which is subsequently ubiquitinated via SCF‐E3 containing ETP1/2F‐box proteins and ultimately degraded via proteasomes. The SCF‐E3–containing EBF1/2F‐box proteins also ubiquitinate EIN3 and EIL1, causing their degradation by the proteasome and in turn preventing the transcription of target genes in the nucleus. The box shows the simplified ethylene biosynthesis pathway in plants. SAM produced from methionine via the Yang cycle is converted to ACC by the enzyme ACS, which is then converted to ethylene by the enzyme ACO. The binding of ethylene causes conformational changes in the receptors, limiting CTR1 activity and thereby preventing EIN2 phosphorylation and subsequent ubiquitination, resulting in increased EIN2 levels. Further, the EIN2 C‐terminal end (EIN2‐C) is released from the N‐terminal end (EIN2‐N) by an as‐yet‐unknown protease. EIN2‐C enables sequestering of EBF1 and EBF2 in P‐bodies, resulting in reduced ubiquitination of EIN3 and EIL1 and, in turn, promoting their levels. EIN2‐C can also translocate to the nucleus to directly promote the transcriptional activity of EIN3/EIL1 and promote ethylene responsive transcriptional changes.
Source: Created with http://BioRender.com.
1.3 Root Development in Plants
1.3.1 Organization of Plant Root Systems
The three‐dimensional structure of a plant root is specified as an RSA that acts as an interface between the plant and the rhizosphere, provides anchorage to the soil, and controls nutrient and water acquisition from the soil. Major factors defining the RSA include primary root length and direction; the number, angle, length, and patterning of lateral roots; and positioning, density, and length of the root hairs (Orman‐Ligeza et al. 2013).
A large portion of our current understanding of root growth and development is derived from studies on the dicot model species A. thaliana (Arabidopsis). Arabidopsis roots follow the typical taproot architecture with a well‐defined structure that serves as an excellent model to study root physiology. The Arabidopsis root is almost transparent and displays a thin anatomy, making it suitable for in‐depth analysis at the tissue and cell‐specific levels. Anatomically, roots are formed by several cell files: the epidermis, cortex, endodermis, and pericycle, arranged as concentric circles in that order with the vasculature located at the core (Dolan et al. 1993). The root tissue can also be differentiated into three distinct zones along the longitudinal axis: the meristematic zone (MZ), elongation zone (EZ), and differentiation zone (DZ). The root stem cells are located at the center in the MZ near the root apex that remains protected from the soil by several layers of cells forming the root cap. Stem cells originating from the meristem differentiate into diverse cell lineages and divide in this region; for example, columella cells are gravity‐sensing cells that contain statoliths (starch‐filled plastids). The cells from the meristem further elongate and gradually differentiate without further cell division in the EZ. As they enter the DZ, cells are already mature and no longer elongate but start forming secondary structures, such as root hairs and fully differentiated xylem. The epidermis differentiates into two types of cells: trichoblasts, the root hairs forming cells, and atrichoblasts, the non‐hair cells. In contrast, the pericycle cells overlaying the xylem pole initiate lateral root formation (Laskowski et al. 1995). The vascular tissues consist of xylem and phloem arranged in a bilateral symmetrical manner so that a central xylem axis is flanked by two phloem poles. A fourth region could also be classified between the MZ and the EZ: the transition zone (TZ), where cells start increasing in length and width by endoreplication processes (Dolan et al. 1993; Ishikawa and Evans 1995; Beemster et al. 2003; Verbelen et al. 2006; Takatsuka and Umeda 2014).
The monocot roots have a more complex architecture, with many showing specialized root branching near the stem called crown roots. Further, the vasculature in monocot roots follows a scattered pattern. Studies with model cereals such as rice and maize have been crucial in understanding the mechanisms of root development in monocots. The genetic mechanisms regulating root development are fairly conserved between dicots and monocots, and the signaling components involved in root organogenesis and root patterning are well understood. Depending on the species, RSAs display high variation in morphological traits that help them adapt to a highly competitive environment. The recent development of newer technologies such as advanced digital photography, 3D root imaging, transparent soils, automated Rhizotron, X‐ray computed tomography, luminescence‐fluorescence based imaging systems, and neutron tomography has enabled us to better understand the architecture of complex root systems (Motte et al. 2019; Tötzke et al. 2019). Therefore, a thorough understanding of the mechanisms involved in adaptive modifications of the RSA holds the potential to improve plant agronomic traits.
1.3.2 Factors Controlling Root Development
Root growth and development is a complex process orchestrated by the interplay between different signaling networks. Extensive studies on the Arabidopsis root system have generated crucial insights into molecular mechanisms regulating root architecture development. Plant hormones are key elements involved in the specification, development, and maintenance of the RAM as well as whole RSA (Jung and McCouch 2013). They regulate the expression of core genes, and their crosstalk is necessary for integrating external and internal signals into those processes. The signaling crosstalk controlling RSA impinges on common regulatory networks of a specific set of genes, ultimately leading to changes at the level of protein functions as well as primary and secondary metabolic conversions (Liu et al. 2014; Sengupta and Reddy 2018).
Auxin is one of the best‐studied hormones for the regulation of root growth and development. Patterns of auxin accumulation determine the positions of embryonic roots and guide the organization of different root zones along the vertical and horizontal axes (Overvoorde et al. 2010). Auxin also controls damage repair in primary roots, tropic root growth, and lateral root spacing and emergence (Reid and Ross 2011). Further, it acts as the ultimate signal at which other signaling pathways converge and regulate different aspects of root architecture (Maurel and Nacry 2020).
Cytokinin is another hormone that has drastic effects on root growth. Cytokinin mainly works antagonistically to auxin to regulate root growth and development. In fact, the spatial and temporal balance between these two hormones is essential to fine‐tune the root architecture to the best fit for its environment (Muraro et al. 2011). For example, cytokinin antagonizes auxin function by transcriptionally regulating the PIN‐FORMED (PIN) proteins, leading to RSA modulation (Lavenus et al. 2016).
Brassinosteroids (BRs) are a set of plant steroid hormones that regulate primary root elongation by controlling both cell elongation and division (Wei and Li 2016; Planas‐Riverola et al. 2019). Besides primary root elongation, BRs can also control other aspects of root development, such as maintenance of meristem size, quiescent center (QC) cell division, root hair formation, lateral root initiation, and root directional growth responses, either independently or in coordination with other signaling pathways (Singh et al. 2014b; Gupta et al. 2015; Wei and Li 2016; Planas‐Riverola et al. 2019).
ABA, which is considered a stress hormone in plants, can also regulate primary and lateral root development. ABA has been reported to show both positive and negative effects on root growth (Li et al. 2017). The gibberellic acid pathway has been reported to control root meristem size through the endodermis (Ubeda‐Tomás et al. 2008; Ubeda‐Tomás et al. 2009).
1.4 Ethylene‐Mediated Regulation of Root Development
The gaseous phytohormone ET has various physiological and morphological effects on plant growth throughout development. In the following section, we will elaborate on ET‐mediated mechanisms involved in controlling different aspects of the RSA (Figure 1.2).
1.4.1 Ethylene and Primary Root Growth
Inhibition of root growth is one of the characteristic effects of ET. Early research conducted on barley and Zea mays revealed that ET inhibits the growth of the seminal axes (Crossett et al. 1975; Whalen and Feldman 1988). More recent studies have demonstrated that exogenous application of ET or its precursor 1‐aminocyclopropane‐1‐carboxylate (ACC) restricts primary root elongation in Arabidopsis and tomatoes (Ruzicka et al. 2007; Negi et al. 2008; Negi et al. 2010). Consistently, Arabidopsis ET overproducer mutant eto1‐1 (ethylene overproducer 1‐1) and the gain of function signaling mutant ctr1‐1 (constitutive triple response 1‐1) exhibit shorter primary roots (Kieber et al. 1993; Vogel et al. 1998; Woeste et al. 1999). In contrast, a genetic mutation in the ET response pathway in the etr1, ein2, ein3, and eil1 mutants; chemical inhibition of ET biosynthesis by 2‐aminoethoxyvinylglycin (AVG) and pyrazinamide (PZA); and ET perception by silver nitrate (AgNO3) and 1‐methylcyclopropene (1‐MCP) promote root elongation (Bleecker et al. 1988; Serek et al. 1995; Le et al. 2001; Ruzicka et al. 2007; Sun et al. 2017). ET suppresses root growth by regulating cell elongation in the EZ (Ruzicka et al. 2007) and cell proliferation in the RAM (Street et al. 2015). ET was shown to restrict the elongation of cells leaving the meristem zone and entering the EZ (Ruzicka et al. 2007). However, more recent reports revealed that ET could also inhibit cell proliferation in the RAM via its canonical response (Street et al. 2015). Further, a cell/tissue‐specific expression approach revealed that ET actions from the epidermal cell files are critical to restrict cell elongation in both roots and shoots (Vaseva et al. 2018).
Figure 1.2 Role of ethylene in the regulation of the root system architecture. This schematic diagram shows the involvement of the ethylene response pathway in root growth and development and its crosstalk with other components. Ethylene primarily utilizes the components of the auxin response pathway to control different aspects of the root system such as primary root growth, lateral root development, root hair elongation, and root directional growth responses. Arrows represent promotion; flat‐ended lines symbolize inhibition; solid lines reflect confirmed interactions; dashed lines represent unresolved or indirect relations.
Source: Created with http://BioRender.com.
Several studies pointed out extensive crosstalk between ET and auxin during root growth. ET has a strong effect on auxin biosynthesis. The WEAK ETHYLENE INSENSITIVE (WEI) genes that are mainly involved in different steps of the auxin biosynthesis pathway were identified in a screen for mutants defective in root‐specific ET responses (Stepanova et al. 2005; Stepanova et al. 2008). ET induces the expression of WEI2 and WEI7, which leads to the accumulation of auxin at the root tip (Stepanova et al. 2005). Similarly, ET response analysis of auxin biosynthesis defective mutants such as tryptophan aminotransferase of arabidopsis 1 (taa1) and the quadruple mutant of YUCCA (yucQ) confirmed the link between local auxin production and tissue‐specific ET effects (Stepanova et al. 2008; Won et al. 2011). ET response pathway transcription factors such as EIN3 and ERF1 can directly bind to the promoters of auxin biosynthesis‐related genes such as YUC9 and ANTHRANILATE SYNTHASE α1 (ASA1), respectively, to regulate differential auxin accumulation in the root (Liu et al. 2016; Mao et al. 2016). Further, chemical inhibitors of auxin biosynthesis such as l‐kynurenine and yucasin were found to inhibit ET responses in roots (He et al. 2011; Nishimura et al. 2014). In addition to controlling auxin biosynthesis and accumulation, ET also controls auxin perception and transport to affect root growth, as mutants related to auxin transport, perception, and signaling are shown to display abnormal responses to ET (Stepanova et al. 2005; Ruzicka et al. 2007). Further, chemical or genetic inhibition of auxin transport, perception, or signaling can also render Arabidopsis roots insensitive to ET (Ruzicka et al. 2007). The auxin receptor mutant transport inhibitor response1 (tir1) and auxin response defective mutants auxin resistant2 (axr2‐1) and axr3‐1 have an ET‐resistance root phenotype (Alonso et al. 2003; Ruzicka et al. 2007; Stepanova et al. 2007). ET also controls auxin transport by regulating the auxin influx carrier AUXIN1 (AUX1) and efflux carrier PIN family proteins. Mutations in the members of these carriers lead to ET‐insensitive primary root phenotype (Stepanova et al. 2007). ET increases auxin transport and transcript levels of AUX1, PIN3, and PIN7 (Zemlyanskaya et al. 2018). ET control over AUX1 is possibly mediated through EIN3, as suggested by the presence of EIN3 binding sites in the promoter region of AUX1 (Chang et al. 2013b). ET regulates PIN2 through ET‐responsive HB52, which transcriptionally modulates PIN2 by directly interacting at its promoter (Miao et al. 2018). Similar studies carried out in monocot plants such as rice, maize, wheat, sorghum, and Brachypodium distachyon also suggest the inhibitory role of ET in controlling root growth mainly via crosstalk with auxin (Yang et al. 2015; Qin et al. 2017; Chen et al. 2018); (Qin et al. 2019).
1.4.2 Ethylene and Lateral Root Development
ET was thought to stimulate lateral root growth in plants such as barley and Z. mays (Crossett et al. 1975; Whalen and Feldman 1988). However, later studies in Arabidopsis and tomato demonstrated its inhibitory effect on lateral root initiation and elongation (Negi et al. 2008; Negi et al. 2010). The ET overproducer mutants eto1‐1 and ctr1‐1 also have decreased lateral root numbers, whereas the etr1 and ein2 mutants form an increased number of lateral roots (Ruzicka et al. 2007). It was observed that ET at low doses has a promotory effect on lateral root initiation, and the inhibitory effect of ET is observed at higher doses (Ivanchenko et al. 2008). It was hypothesized that ET produced in differentiating protoxylem vessels near the root tip might be the signal that triggers the process of lateral root initiation at the xylem pole (Aloni et al. 2006). Many evidences supported this hypothesis. Pesquet and Tuominen (2011) found that ET is produced in maturing vessel elements, indicating that a differentiating protoxylem vessel at the root tip can produce a low amount of ET. Moreover, the expression patterns of the ET biosynthesis genes belonging to the ACC SYNTHASE family (ACS2, ACS5, ACS6, ACS7, and ACS8) and an APETALA2/ERE encoding gene PUCHI hinted at the potential accumulation of ET, albeit at lower levels, in lateral root founder cells of pericycle (Tsuchisaka and Theologis 2004; Hirota et al. 2007). Auxin promotes ET production in xylem vessels. The compact structure of the endodermis blocks the further diffusion of ET into the cortex, which causes local accumulation of ET in the pericycle. ET inhibits elongation of the xylem‐adjacent pericycle cells at the lateral root initiation site (Ivanchenko et al. 2008). It can also control lateral root initiation and development by regulating auxin distribution and accumulation patterns (Ivanchenko et al. 2008; Negi et al. 2008; Lewis et al. 2011; Aloni 2013). In the root pericycle, ET inhibits the polar movement of low‐concentration indole acetic acid (IAA) adjacent to the differentiating protoxylem vessel. This allows the buildup of fresh IAA transported from young leaves, adjacent to this IAA inhibition site in the pericycle, and stimulates cell division to give rise to the founder cells of a new lateral root (Lewis et al. 2011; Aloni 2013). ET at higher doses can also antagonize glucose‐induced lateral root production (Singh et al. 2015).
1.4.3 Ethylene and Root Hair Development
ET has long been known as a positive influencer of root hair cell fate and differentiation (Dolan et al. 1995; Tanimoto et al. 1995). ACC treatment causes abundant root‐hair formation at otherwise non‐root‐hair‐forming cell files, leading to an overall increase in the number of root hairs in Arabidopsis (Tanimoto et al. 1995). While the ein2 mutant displays a clear short‐root‐hair phenotype, the ctr1 loss‐of‐function mutation promotes root hair elongation in Arabidopsis (Masucci and Schiefelbein 1996; Pitts et al. 1998). Whereas the exogenous application of ET/ACC and constitutively activated ET signaling promoted root hair elongation, application of ET biosynthesis or signaling inhibitors and the ET‐response defective mutants displayed significantly shorter root hairs (Song et al. 2016; Zhang et al. 2016; Feng et al. 2017).
ET also utilizes auxin‐mediated mechanisms to regulate root hair growth in a synergistic manner (Pitts et al. 1998). Auxin treatment could rescue root hair defects of the ET signaling mutant ein2‐1, and the long‐root‐hair phenotypes of the ET overproducer mutant eto1 were suppressed by auxin response defective aux1 mutant (Strader et al. 2010).
In Arabidopsis, a C2H2 transcription factor ZINC FINGER PROTEIN 5 (ZFP5) was also found to be involved in ET mediated root hair elongation, as the zfp5‐4 loss‐of‐function mutant did not show root hair elongation after ACC treatment. However, this regulation was independent of the ectopic root hair formation upon ACC application (An et al. 2012). ACC treatment promotes ROOT HAIR DEFECTIVE 6‐LIKE 4 (RSL4) expression (Zhang et al. 2016). ET executes its function on root hair development mainly via EIN3/EIL1‐mediated mechanisms. Both EIN3 and EIL1 are necessary for ET‐mediated induction of the hair‐elongation factor RSL4 (Feng et al. 2017). EIN3 can also physically interact with ROOT HAIR DEFECTIVE6 (RHD6) to promote RSL4. The coordinated actions of EIN3/EIL1 and RHD6/RSL1 are found to be crucial in defining the root hair initiation (Feng et al. 2017).
1.4.4 Ethylene and Tropic Responses of RSA
In maize, ET biosynthesis or signaling inhibition led to reduced root gravitropic curvature (Lee and Evans 1990). ET may regulate the root gravitropic response by affecting starch metabolism, as exogenous ET not only reduced the magnitude of gravitropic bending but also modulated the starch levels in Arabidopsis root columella cells (Guisinger and Kiss 1999). However, most studies of ET control of root gravitropism revealed its crosstalk with auxin (Nziengui et al. 2018). In Arabidopsis, the ET‐ and auxin‐defective 1‐aminocyclopropane‐1‐carboxylic acid‐related long hypocotyl 1 (alh1) mutant responded faster to gravi‐stimulation (Vandenbussche et al. 2003). ET was found to inhibit root gravitropic curvature by delaying the asymmetric auxin distribution upon gravity stimulation (Buer et al. 2006). Further, this ET‐induced inhibition of root gravitropism was absent in ET‐signaling‐defective etr1‐3 and ein2‐5 mutants (Buer et al. 2006). The ET biosynthesis defective acs7‐1 mutant showed reduced sensitivity to ethylene glycol‐bis‐(aminoethyl ether)‐N,N'‐tetraacetic acid (EGTA)‐ and naphthylphthalamic acid (NPA)‐mediated root gravitropism inhibition that could be restored by ACC application (Huang et al. 2013). The Arabidopsis ET‐resistant mutants in root handedness 1 (rha1), encoding a heat‐shock factor, displayed perturbed responses in terms of roots slanting and gravitropism along with other defects in the auxin response (Fortunati et al. 2008). These results confirm that ET signaling components are essential for a normal root gravitropic response. More recent studies in Arabidopsis also provided evidence of other mechanisms involving actin cytoskeleton rearrangement in the root TZ during ET‐mediated gravitropic bending response in Arabidopsis (Pozhvanov et al. 2016).
ET can also regulate other root directional growth responses such as root waving and skewing (Buer 2003; Oliva and Dunand 2007). ET suppressed root looping in the presence of sucrose and upon high nutrient availability (Buer 2003). ET also controls thigmotropism responses to control root penetration in the growth substance. In Arabidopsis, a sudden encounter with a rigid medium reduced ACC levels at the root tip. The resulting lower ET levels softened the root tip, enabling a slip or bend. Interestingly, the roots that did not bend had higher ET levels and harder root tips for better medium penetration (Yamamoto et al. 2008). During tomato seed germination, ET and auxin crosstalk is shown to be essential for better soil penetration of emerging roots. The ET perception defective Never‐ripe mutant displayed poor penetrance to the soil, whereas the roots of the polycotyledon mutant with enhanced polar auxin transport were able to penetrate soil normally even upon ET inhibition (Santisree et al. 2011). Further, exogenous application of ACC was enough to abolish the sugar‐ and BR‐mediated root directional growth response in Arabidopsis seedlings (Singh et al. 2014a). ET has also been implicated in other tropic responses of the root, such as hydrotropism and halotropism (Muthert et al. 2020).
1.5 Conclusions and Future Perspectives
Roots are the most versatile and flexible plant systems to study and manipulate, as root growth and development occur in both the radial and longitudinal axes throughout the life of the plant. Further, spatiotemporal regulation of cellular processes at the root stem cell niche and in different cell types is crucial for root architecture development. Based on previous and recent findings, it is clear that ET is an essential player in such spatiotemporal signaling events controlling root development. ET not only plays a crucial role in the developmental aspect of the RSA but also helps maintain optimal root growth direction and structure necessary for water and nutrient foraging (Figure 1.2). Moreover, ET has also shown a prominent role in plant responses to different abiotic stresses (Tao et al. 2015; Iqbal et al. 2017; Pan et al. 2019; Sytar et al. 2019; Wang and Huang 2019; Wang et al. 2020).
The synthesis of ET is controlled by several stress factors such as submergence, hypoxia, heat, salinity, and drought stress (Gunawardena et al. 2001; Larrainzar et al. 2014; Li et al. 2015; Salazar et al. 2015). Plants have developed the ET pathway as a possible mode for coping with the environment beneath and above the soil by helping seedlings modulate their differential growth. Since ET is essential for root architecture maintenance, understanding how it coordinates growth responses at cell‐specific levels and under various growth environments will drive the generation of tools that enable plants with more adaptable root architectures. Thus, understanding the interaction of ET with plant roots may help combat climate change.
References
Aloni, R. (2013). Role of hormones in controlling vascular differentiation and the mechanism of lateral root initiation.
Planta
238: 819–830.
Aloni, R., Aloni, E., Langhans, M., and Ullrich, C.I. (2006). Role of cytokinin and auxin in shaping root architecture: regulating vascular differentiation, lateral root initiation, root apical dominance and root gravitropism.
Ann. Bot.
97: 883–893.
Alonso, J.M., Stepanova, A.N., Solano, R. et al. (2003). Five components of the ethylene‐response pathway identified in a screen for weak ethylene‐insensitive mutants in
Arabidopsis
.
Proc Natl Acad Sci USA
100: 2992–2997.
An, L., Zhou, Z., Sun, L. et al. (2012). A zinc finger protein gene ZFP5 integrates phytohormone signaling to control root hair development in
Arabidopsis
.
Plant J
72: 474–490.
Bakshi, A., Piya, S., Fernandez, J.C. et al. (2018). Ethylene receptors signal via a noncanonical pathway to regulate abscisic acid responses.
Plant Physiol
176: 910–929.
Beemster, G.T., Fiorani, F., and Inze, D. (2003). Cell cycle: the key to plant growth control?
Trends Plant Sci
8: 154–158.
Binder, B.M., Chang, C., and Schaller, G.E. (2018). Perception of ethylene by plants–ethylene receptors.
Annual Plant Reviews
44: 117–145.
Bleecker, A.B., Estelle, M.A., Somerville, C., and Kende, H. (1988). Insensitivity to ethylene conferred by a dominant mutation in
Arabidopsis thaliana
.
Science
241: 1086–1089.
Buer, C.S. (2003). Ethylene modulates root‐wave responses in
Arabidopsis
.
Plant Physiol.
132: 1085–1096.
Buer, C.S., Sukumar, P., and Muday, G.K. (2006). Ethylene modulates flavonoid accumulation and gravitropic responses in roots of
Arabidopsis
.
Plant Physiol.
140: 1384–1396.
Chang, K.N., Zhong, S., Weirauch, M.T. et al. (2013). Temporal transcriptional response to ethylene gas drives growth hormone cross‐regulation in
Arabidopsis
.
Elife
2: e00675.
Chen, H., Ma, B., Zhou, Y. et al. (2018). E3 ubiquitin ligase SOR1 regulates ethylene response in rice root by modulating stability of Aux/IAA protein.
Proc Natl Acad Sci USA
115: 4513–4518.
Crossett, R. and Campbell, D.J. (1975). The effects of ethylene in the root environment upon the development of barley.
Plant Soil
42: 453–464.
Dolan, L. and Roberts, K. (1995). The development of cell pattern in the root epidermis.
Philos Trans R Soc Lond B Biol Sci
350: 95–99.
Dolan, L., Janmaat, K., Willemsen, V. et al. (1993). Cellular organisation of the
Arabidopsis thaliana
root.
Development
119: 71–84.
Dubois, M., Van den Broeck, L., and Inzé, D. (2018). The pivotal role of ethylene in plant growth.
Trends Plant Sci.
23: 311–323.
Feng, Y., Xu, P., Li, B. et al. (2017). Ethylene promotes root hair growth through coordinated EIN3/EIL1 and RHD6/RSL1 activity in
Arabidopsis
.
Proc Natl Acad Sci USA
114: 13834–13839.
Fortunati, A., Piconese, S., Tassone, P. et al. (2008). A new mutant of
Arabidopsis
disturbed in its roots, right‐handed slanting, and gravitropism defines a gene that encodes a heat‐shock factor.
J. Exp. Bot.
59: 1363–1374.
Guisinger, M.M. and Kiss, J.Z. (1999). The influence of microgravity and spaceflight on columella cell ultrastructure in starch‐deficient mutants of
Arabidopsis
.
Am. J. Bot.
86: 1357–1366.
Gunawardena, A.H., Pearce, D.M., Jackson, M.B. et al. (2001). Share characterisation of programmed cell death during aerenchyma formation induced by ethylene or hypoxia in roots of maize (
Zea mays
L.).
Planta
212 (2): 205–214.
Guo, H. and Ecker, J.R. (2003). Plant responses to ethylene gas are mediated by SCFEBF1/EBF2‐dependent proteolysis of EIN3 transcription factor.
Cell
115: 667–677.
Guo, H. and Ecker, J.R. (2004). The ethylene signaling pathway: new insights.
Curr. Opin. Plant Biol.
7: 40–49.
Gupta, A., Singh, M., and Laxmi, A. (2015). Interaction between glucose and Brassinosteroid during the regulation of lateral root development in
Arabidopsis
.
Plant Physiol.
168: 307–320.
He, W., Brumos, J., Li, H. et al. (2011). A small‐molecule screen identifies L‐kynurenine as a competitive inhibitor of TAA1/TAR activity in ethylene‐directed auxin biosynthesis and root growth in
Arabidopsis
.
Plant Cell
23: 3944–3960.
Hirota, A., Kato, T., Fukaki, H. et al. (2007). The auxin‐regulated AP2/EREBP Gene
PUCHI
is required for morphogenesis in the early lateral root primordium of
Arabidopsis
.
Plant Cell
19: 2156–2168.
Huang, S.‐J., Chang, C.‐L., Wang, P.‐H. et al. (2013). A type III ACC synthase, ACS7, is involved in root gravitropism in
Arabidopsis thaliana
.
J. Exp. Bot.
64: 4343–4360.
