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Phytohormones 2020

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A special issue of Biomolecules (ISSN 2218-273X). This special issue belongs to the section "Natural and Bio-inspired Molecules".

Deadline for manuscript submissions: closed (15 January 2021) | Viewed by 65748

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Special Issue Editor

Prof. Dr. Guzel Kudoyarova

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Guest Editor

Laboratory of Plant Physiology, Ufa Institute of Biology of the Russian Academy of Sciences, Ufa 450054, Russia
Interests: plant productivity; phytohormones; plant growth promoting bacteria; bacterial metabolites; plant-microorganism interaction
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Special Issue Information

Dear Colleagues,

The hormonal system plays a decisive role in the control of plant growth and development. Alongside classical plant hormones (auxins, cytokinins, gibberellins, abscisic acid), hormonal function is now attributed to jasmonates, salicylic acid, and brassinosteroids. Plant hormones are capable of influencing vital processes, including plant growth and development, adaptation to environment, and resistance to biotic and abiotic stresses and productivity. In accordance, plant hormones are attractive tools for biotechnology aimed at improving plant performance in accordance with human needs. Thus, synthesis of plant hormones by rhizosphere microorganisms is the base for their capacity to promote plant growth as well as for application of their preparations in crop production. Still, the success of the use of plant hormones depends on the knowledge of the mechanisms of their action. Advances in the study of plants hormones include discovery of their receptors and cascades of hormonal signal transduction, identification of their target genes and those controlling hormonal metabolism and signaling, revealing cross-talk between hormones and their interaction with calcium, reactive oxygen species, and nitrogen oxide signaling.

We invite investigators to contribute high-quality original research and review articles focused on the implication of plant hormones in plant growth and development, their adaptation to the environment and resistance to abiotic and biotic stresses (molecular, cellular, and whole plant aspects of the problems), cross-talk between plant hormones and their interaction with other signaling systems, and the importance of hormones for plant growth promotion by soil microorganisms.

A previous Special Issue on Phytohormones already appeared in 2019 (see: https://www.mdpi.com/journal/biomolecules/special_issues/biomolecules_phytohormones), and many interesting articles were submitted, accepted, and published. Our team did its best to simplify and speed up the processing of articles, and the comments of our invited reviewers helped to improve their quality. Many of them were accepted for publication no later than a month after their initial submission. We will aim to provide the same level of service this time around.

Dr. Guzel Kudoyarova
Guest Editor

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Keywords

auxins
cytokinins
gibberellins
abscisic acid
ethylene
jasmonates
salicylic acid
brassinosteroids
hormonal signaling
metabolism of hormones
hormonal target genes
hormonal control of plant growth and development
resistance
productivity

Published Papers (14 papers)

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Editorial

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4 pages, 180 KiB

Open AccessEditorial

Phytohormones 2020

by Guzel Kudoyarova

Biomolecules 2022, 12(9), 1305; https://doi.org/10.3390/biom12091305 - 16 Sep 2022

Cited by 1 | Viewed by 1504

Abstract

The hormonal system plays a decisive role in the control of plant growth and development [...] Full article

(This article belongs to the Special Issue Phytohormones 2020)

Research

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16 pages, 2517 KiB

Open AccessFeature PaperArticle

Rhizosphere Bacterium Rhodococcus sp. P1Y Metabolizes Abscisic Acid to Form Dehydrovomifoliol

by Oleg S. Yuzikhin, Natalia E. Gogoleva, Alexander I. Shaposhnikov, Tatyana A. Konnova, Elena V. Osipova, Darya S. Syrova, Elena A. Ermakova, Valerii P. Shevchenko, Igor Yu. Nagaev, Konstantin V. Shevchenko, Nikolay F. Myasoedov, Vera I. Safronova, Alexey L. Shavarda, Anton A. Nizhnikov, Andrey A. Belimov and Yuri V. Gogolev

Biomolecules 2021, 11(3), 345; https://doi.org/10.3390/biom11030345 - 25 Feb 2021

Cited by 18 | Viewed by 3036

Abstract

The phytohormone abscisic acid (ABA) plays an important role in plant growth and in response to abiotic stress factors. At the same time, its accumulation in soil can negatively affect seed germination, inhibit root growth and increase plant sensitivity to pathogens. ABA is an inert compound resistant to spontaneous hydrolysis and its biological transformation is scarcely understood. Recently, the strain Rhodococcus sp. P1Y was described as a rhizosphere bacterium assimilating ABA as a sole carbon source in batch culture and affecting ABA concentrations in plant roots. In this work, the intermediate product of ABA decomposition by this bacterium was isolated and purified by preparative HPLC techniques. Proof that this compound belongs to ABA derivatives was carried out by measuring the molar radioactivity of the conversion products of this phytohormone labeled with tritium. The chemical structure of this compound was determined by instrumental techniques including high-resolution mass spectrometry, NMR spectrometry, FTIR and UV spectroscopies. As a result, the metabolite was identified as (4RS)-4-hydroxy-3,5,5-trimethyl-4-[(E)-3-oxobut-1-enyl]cyclohex-2-en-1-one (dehydrovomifoliol). Based on the data obtained, it was concluded that the pathway of bacterial degradation and assimilation of ABA begins with a gradual shortening of the acyl part of the molecule. Full article

(This article belongs to the Special Issue Phytohormones 2020)

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24 pages, 2491 KiB

Open AccessArticle

Nitric Oxide Enhances Photosynthetic Nitrogen and Sulfur-Use Efficiency and Activity of Ascorbate-Glutathione Cycle to Reduce High Temperature Stress-Induced Oxidative Stress in Rice (Oryza sativa L.) Plants

by Harsha Gautam, Zebus Sehar, Md Tabish Rehman, Afzal Hussain, Mohamed F. AlAjmi and Nafees A. Khan

Biomolecules 2021, 11(2), 305; https://doi.org/10.3390/biom11020305 - 18 Feb 2021

Cited by 32 | Viewed by 4350

Abstract

The effects of nitric oxide (NO) as 100 µM sodium nitroprusside (SNP, NO donor) on photosynthetic-nitrogen use efficiency (NUE), photosynthetic-sulfur use efficiency (SUE), photosynthesis, growth and agronomic traits of rice (Oryza sativa L.) cultivars, Taipie-309 (high photosynthetic-N and SUE) and Rasi (low photosynthetic-N and SUE) were investigated under high temperature stress (40 °C for 6 h). Plants exposed to high temperature stress caused significant reduction in photosynthetic activity, use efficiency of N and S, and increment in H₂O₂ and thiobarbituric acid reactive substance (TBARS) content. The drastic effects of high temperature stress were more pronounced in cultivar Rasi than Taipie-309. However, foliar spray of SNP decreased the high temperature induced H₂O₂ and TBARS content and increased accumulation of proline and activity of ascorbate–glutathione cycle that collectively improved tolerance to high temperature stress more effectively in Taipie-309. Exogenously applied SNP alleviated the high temperature induced decrease in photosynthesis through maintaining higher photosynthetic-NUE and photosynthetic-SUE, activity of ribulose 1,5 bisphosphate carboxylase/oxygenase (Rubisco), and synthesis of reduced glutathione (GSH). The use of 2-4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxy-3-oxide (cPTIO, NO scavenger) substantiated the study that in the absence of NO oxidative stress increased, while NO increased photosynthetic-NUE and photosynthetic-SUE, net photosynthesis and plant dry mass. Taken together, the present investigation reveals that NO increased heat stress tolerance and minimized high temperature stress adversaries more effectively in cultivar Taipie-309 than Rasi by enhancing photosynthetic-NUE and SUE and strengthening the antioxidant defense system. Full article

(This article belongs to the Special Issue Phytohormones 2020)

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31 pages, 4392 KiB

Open AccessFeature PaperArticle

Ethylene-Cytokinin Interaction Determines Early Defense Response of Wheat against Stagonospora nodorum Berk.

by Svetlana V. Veselova, Tatyana V. Nuzhnaya, Guzel F. Burkhanova, Sergey D. Rumyantsev, Elza K. Khusnutdinova and Igor V. Maksimov

Biomolecules 2021, 11(2), 174; https://doi.org/10.3390/biom11020174 - 28 Jan 2021

Cited by 18 | Viewed by 2745

Abstract

Ethylene, salicylic acid (SA), and jasmonic acid are the key phytohormones involved in plant immunity, and other plant hormones have been demonstrated to interact with them. The classic phytohormone cytokinins are important participants of plant defense signaling. Crosstalk between ethylene and cytokinins has not been sufficiently studied as an aspect of plant immunity and is addressed in the present research. We compared expression of the genes responsible for hormonal metabolism and signaling in wheat cultivars differing in resistance to Stagonospora nodorum in response to their infection with fungal isolates, whose virulence depends on the presence of the necrotrophic effector SnTox3. Furthermore, we studied the action of the exogenous cytokinins, ethephon (2-chloroethylphosphonic acid, ethylene-releasing agent) and 1-methylcyclopropene (1-MCP, inhibitor of ethylene action) on infected plants. Wheat susceptibility was shown to develop due to suppression of reactive oxygen species production and decreased content of active cytokinins brought about by SnTox3-mediated activation of the ethylene signaling pathway. SnTox3 decreased cytokinin content most quickly by its activated glucosylation in an ethylene-dependent manner and, furthermore, by oxidative degradation and inhibition of biosynthesis in ethylene-dependent and ethylene-independent manners. Exogenous zeatin application enhanced wheat resistance against S. nodorum through inhibition of the ethylene signaling pathway and upregulation of SA-dependent genes. Thus, ethylene inhibited triggering of SA-dependent resistance mechanism, at least in part, by suppression of the cytokinin signaling pathway. Full article

(This article belongs to the Special Issue Phytohormones 2020)

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20 pages, 3239 KiB

Open AccessArticle

Molecular Dynamics of Chloroplast Membranes Isolated from Wild-Type Barley and a Brassinosteroid-Deficient Mutant Acclimated to Low and High Temperatures

by Iwona Sadura, Dariusz Latowski, Jana Oklestkova, Damian Gruszka, Marek Chyc and Anna Janeczko

Biomolecules 2021, 11(1), 27; https://doi.org/10.3390/biom11010027 - 29 Dec 2020

Cited by 11 | Viewed by 2634

Abstract

Plants have developed various acclimation strategies in order to counteract the negative effects of abiotic stresses (including temperature stress), and biological membranes are important elements in these strategies. Brassinosteroids (BR) are plant steroid hormones that regulate plant growth and development and modulate their reaction against many environmental stresses including temperature stress, but their role in modifying the properties of the biological membrane is poorly known. In this paper, we characterise the molecular dynamics of chloroplast membranes that had been isolated from wild-type and a BR-deficient barley mutant that had been acclimated to low and high temperatures in order to enrich the knowledge about the role of BR as regulators of the dynamics of the photosynthetic membranes. The molecular dynamics of the membranes was investigated using electron paramagnetic resonance (EPR) spectroscopy in both a hydrophilic and hydrophobic area of the membranes. The content of BR was determined, and other important membrane components that affect their molecular dynamics such as chlorophylls, carotenoids and fatty acids in these membranes were also determined. The chloroplast membranes of the BR-mutant had a higher degree of rigidification than the membranes of the wild type. In the hydrophilic area, the most visible differences were observed in plants that had been grown at 20 °C, whereas in the hydrophobic core, they were visible at both 20 and 5 °C. There were no differences in the molecular dynamics of the studied membranes in the chloroplast membranes that had been isolated from plants that had been grown at 27 °C. The role of BR in regulating the molecular dynamics of the photosynthetic membranes will be discussed against the background of an analysis of the photosynthetic pigments and fatty acid composition in the chloroplasts. Full article

(This article belongs to the Special Issue Phytohormones 2020)

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28 pages, 5090 KiB

Open AccessArticle

Cytokinin N-glucosides: Occurrence, Metabolism and Biological Activities in Plants

by Eva Pokorná, Tomáš Hluska, Petr Galuszka, H. Tucker Hallmark, Petre I. Dobrev, Lenka Záveská Drábková, Tomáš Filipi, Katarína Holubová, Ondřej Plíhal, Aaron M. Rashotte, Roberta Filepová, Jiří Malbeck, Ondřej Novák, Lukáš Spíchal, Břetislav Brzobohatý, Pavel Mazura, Lenka Zahajská and Václav Motyka

Biomolecules 2021, 11(1), 24; https://doi.org/10.3390/biom11010024 - 28 Dec 2020

Cited by 22 | Viewed by 5247

Abstract

Cytokinins (CKs) are a class of phytohormones affecting many aspects of plant growth and development. In the complex process of CK homeostasis in plants, N-glucosylation represents one of the essential metabolic pathways. Its products, CK N7- and N9-glucosides, have been largely overlooked in the past as irreversible and inactive CK products lacking any relevant physiological impact. In this work, we report a widespread distribution of CK N-glucosides across the plant kingdom proceeding from evolutionary older to younger plants with different proportions between N7- and N9-glucosides in the total CK pool. We show dramatic changes in their profiles as well as in expression levels of the UGT76C1 and UGT76C2 genes during Arabidopsis ontogenesis. We also demonstrate specific physiological effects of CK N-glucosides in CK bioassays including their antisenescent activities, inhibitory effects on root development, and activation of the CK signaling pathway visualized by the CK-responsive YFP reporter line, TCSv2::3XVENUS. Last but not least, we present the considerable impact of CK N7- and N9-glucosides on the expression of CK-related genes in maize and their stimulatory effects on CK oxidase/dehydrogenase activity in oats. Our findings revise the apparent irreversibility and inactivity of CK N7- and N9-glucosides and indicate their involvement in CK evolution while suggesting their unique function(s) in plants. Full article

(This article belongs to the Special Issue Phytohormones 2020)

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18 pages, 4035 KiB

Open AccessFeature PaperArticle

Cytokinin-Regulated Expression of Arabidopsis thaliana PAP Genes and Its Implication for the Expression of Chloroplast-Encoded Genes

by Aleksandra A. Andreeva, Radomira Vankova, Ivan A. Bychkov, Natalia V. Kudryakova, Maria N. Danilova, Jozef Lacek, Elena S. Pojidaeva and Victor V. Kusnetsov

Biomolecules 2020, 10(12), 1658; https://doi.org/10.3390/biom10121658 - 11 Dec 2020

Cited by 13 | Viewed by 2394

Abstract

Cytokinins (CKs) are known to regulate the biogenesis of chloroplasts under changing environmental conditions and at different stages of plant ontogenesis. However, the underlying mechanisms are still poorly understood. Apparently, the mechanisms can be duplicated in several ways, including the influence of nuclear genes that determine the expression of plastome through the two-component CK regulatory circuit. In this study, we evaluated the role of cytokinins and CK signaling pathway on the expression of nuclear genes for plastid RNA polymerase-associated proteins (PAPs). Cytokinin induced the expression of all twelve Arabidopsis thalianaPAP genes irrespective of their functions via canonical CK signaling pathway but this regulation might be indirect taking into consideration their different functions and versatile structure of promoter regions. The disruption of PAP genes contributed to the abolishment of positive CK effect on the accumulation of the chloroplast gene transcripts and transcripts of the nuclear genes for plastid transcription machinery as can be judged from the analysis of pap1 and pap6 mutants. However, the CK regulatory circuit in the mutants remained practically unperturbed. Knock-out of PAP genes resulted in cytokinin overproduction as a consequence of the strong up-regulation of the genes for CK synthesis. Full article

(This article belongs to the Special Issue Phytohormones 2020)

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12 pages, 2162 KiB

Open AccessArticle

Rhizobacteria Inoculation Effects on Phytohormone Status of Potato Microclones Cultivated In Vitro under Osmotic Stress

by Tatiana N. Arkhipova, Nina V. Evseeva, Oksana V. Tkachenko, Gennady L. Burygin, Lidiya B. Vysotskaya, Zarina A. Akhtyamova and Guzel R. Kudoyarova

Biomolecules 2020, 10(9), 1231; https://doi.org/10.3390/biom10091231 - 24 Aug 2020

Cited by 23 | Viewed by 2903

Abstract

Water deficits inhibit plant growth and decrease crop productivity. Remedies are needed to counter this increasingly urgent problem in practical farming. One possible approach is to utilize rhizobacteria known to increase plant resistance to abiotic and other stresses. We therefore studied the effects of inoculating the culture medium of potato microplants grown in vitro with Azospirillum brasilense Sp245 or Ochrobactrum cytisi IPA7.2. Growth and hormone content of the plants were evaluated under stress-free conditions and under a water deficit imposed with polyethylene glycol (PEG 6000). Inoculation with either bacterium promoted the growth in terms of leaf mass accumulation. The effects were associated with increased concentrations of auxin and cytokinin hormones in the leaves and stems and with suppression of an increase in the leaf abscisic acid that PEG treatment otherwise promoted in the potato microplants. O. cytisi IPA7.2 had a greater growth-stimulating effect than A. brasilense Sp245 on stressed plants, while A. brasilense Sp245 was more effective in unstressed plants. The effects were likely to be the result of changes to the plant’s hormonal balance brought about by the bacteria. Full article

(This article belongs to the Special Issue Phytohormones 2020)

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19 pages, 2461 KiB

Open AccessArticle

Effects of Jasmonic Acid in ER Stress and Unfolded Protein Response in Tomato Plants

by Zalán Czékus, Orsolya Csíkos, Attila Ördög, Irma Tari and Péter Poór

Biomolecules 2020, 10(7), 1031; https://doi.org/10.3390/biom10071031 - 10 Jul 2020

Cited by 10 | Viewed by 2957

Abstract

Endoplasmic reticulum (ER) stress elicits a protective mechanism called unfolded protein response (UPR) to maintain cellular homeostasis, which can be regulated by defence hormones. In this study, the physiological role of jasmonic acid (JA) in ER stress and UPR signalling has been investigated in intact leaves of tomato plants. Exogenous JA treatments not only induced the transcript accumulation of UPR marker gene SlBiP but also elevated transcript levels of SlIRE1 and SlbZIP60. By the application of JA signalling mutant jai1 plants, the role of JA in ER stress sensing and signalling was further investigated. Treatment with tunicamycin (Tm), the inhibitor of N-glycosylation of secreted glycoproteins, increased the transcript levels of SlBiP. Interestingly, SlIRE1a and SlIRE1b were significantly lower in jai1. In contrast, the transcript accumulation of Bax Inhibitor-1 (SlBI1) and SlbZIP60 was higher in jai1. To evaluate how a chemical chaperone modulates Tm-induced ER stress, plants were treated with sodium 4-phenylbutyrate, which also decreased the Tm-induced increase in SlBiP, SlIRE1a, and SlBI1 transcripts. In addition, it was found that changes in hydrogen peroxide content, proteasomal activity, and lipid peroxidation induced by Tm is regulated by JA, while nitric oxide was not involved in ER stress and UPR signalling in leaves of tomato. Full article

(This article belongs to the Special Issue Phytohormones 2020)

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25 pages, 4462 KiB

Open AccessArticle

Transcriptome Analysis Reveals Potential Roles of Abscisic Acid and Polyphenols in Adaptation of Onobrychis viciifolia to Extreme Environmental Conditions in the Qinghai-Tibetan Plateau

by Hengxia Yin, Huakun Zhou, Wenying Wang, Lam-Son Phan Tran and Benyin Zhang

Biomolecules 2020, 10(6), 967; https://doi.org/10.3390/biom10060967 - 26 Jun 2020

Cited by 7 | Viewed by 2738

Abstract

A detailed understanding of the molecular mechanisms of plant stress resistance in the face of ever-changing environmental stimuli will be helpful for promoting the growth and production of crop and forage plants. Investigations of plant responses to various single abiotic or biotic factors, or combined stresses, have been extensively reported. However, the molecular mechanisms of plants in responses to environmental stresses under natural conditions are not clearly understood. In this study, we carried out a transcriptome analysis using RNA-sequencing to decipher the underlying molecular mechanisms of Onobrychis viciifolia responding and adapting to the extreme natural environment in the Qinghai-Tibetan Plateau (QTP). The transcriptome data of plant samples collected from two different altitudes revealed a total of 8212 differentially expressed genes (DEGs), including 5387 up-regulated and 2825 down-regulated genes. Detailed analysis of the identified DEGs uncovered that up-regulation of genes potentially leading to changes in hormone homeostasis and signaling, particularly abscisic acid-related ones, and enhanced biosynthesis of polyphenols play vital roles in the adaptive processes of O. viciifolia. Interestingly, several DEGs encoding uridine diphosphate glycosyltransferases, which putatively regulate phytohormone homeostasis to resist environmental stresses, were also discovered. Furthermore, numerous DEGs encoding transcriptional factors, such as members of the myeloblastosis (MYB), homeodomain-leucine zipper (HD-ZIP), WRKY, and nam-ataf1,2-cuc2 (NAC) families, might be involved in the adaptive responses of O. viciifolia to the extreme natural environmental conditions. The DEGs identified in this study represent candidate targets for improving environmental stress resistance of O. viciifolia grown in higher altitudes of the QTP, and can provide deep insights into the molecular mechanisms underlying the responses of this plant species to the extreme natural environmental conditions of the QTP. Full article

(This article belongs to the Special Issue Phytohormones 2020)

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Review

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38 pages, 2533 KiB

Open AccessFeature PaperEditor’s ChoiceReview

The Hulks and the Deadpools of the Cytokinin Universe: A Dual Strategy for Cytokinin Production, Translocation, and Signal Transduction

by Tomáš Hluska, Lucia Hlusková and R. J. Neil Emery

Biomolecules 2021, 11(2), 209; https://doi.org/10.3390/biom11020209 - 03 Feb 2021

Cited by 30 | Viewed by 6142

Abstract

Cytokinins are plant hormones, derivatives of adenine with a side chain at the N⁶-position. They are involved in many physiological processes. While the metabolism of trans-zeatin and isopentenyladenine, which are considered to be highly active cytokinins, has been extensively studied, there are others with less obvious functions, such as cis-zeatin, dihydrozeatin, and aromatic cytokinins, which have been comparatively neglected. To help explain this duality, we present a novel hypothesis metaphorically comparing various cytokinin forms, enzymes of CK metabolism, and their signalling and transporter functions to the comics superheroes Hulk and Deadpool. Hulk is a powerful but short-lived creation, whilst Deadpool presents a more subtle and enduring force. With this dual framework in mind, this review compares different cytokinin metabolites, and their biosynthesis, translocation, and sensing to illustrate the different mechanisms behind the two CK strategies. This is put together and applied to a plant developmental scale and, beyond plants, to interactions with organisms of other kingdoms, to highlight where future study can benefit the understanding of plant fitness and productivity. Full article

(This article belongs to the Special Issue Phytohormones 2020)

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21 pages, 3049 KiB

Open AccessReview

Jasmonates, Ethylene and Brassinosteroids Control Adventitious and Lateral Rooting as Stress Avoidance Responses to Heavy Metals and Metalloids

by Camilla Betti, Federica Della Rovere, Diego Piacentini, Laura Fattorini, Giuseppina Falasca and Maria Maddalena Altamura

Biomolecules 2021, 11(1), 77; https://doi.org/10.3390/biom11010077 - 08 Jan 2021

Cited by 41 | Viewed by 4746

Abstract

Developmental and environmental signaling networks often converge during plant growth in response to changing conditions. Stress-induced hormones, such as jasmonates (JAs), can influence growth by crosstalk with other signals like brassinosteroids (BRs) and ethylene (ET). Nevertheless, it is unclear how avoidance of an abiotic stress triggers local changes in development as a response. It is known that stress hormones like JAs/ET and BRs can regulate the division rate of cells from the first asymmetric cell divisions (ACDs) in meristems, suggesting that stem cell activation may take part in developmental changes as a stress-avoidance-induced response. The root system is a prime responder to stress conditions in soil. Together with the primary root and lateral roots (LRs), adventitious roots (ARs) are necessary for survival in numerous plant species. AR and LR formation is affected by soil pollution, causing substantial root architecture changes by either depressing or enhancing rooting as a stress avoidance/survival response. Here, a detailed overview of the crosstalk between JAs, ET, BRs, and the stress mediator nitric oxide (NO) in auxin-induced AR and LR formation, with/without cadmium and arsenic, is presented. Interactions essential in achieving a balance between growth and adaptation to Cd and As soil pollution to ensure survival are reviewed here in the model species Arabidopsis and rice. Full article

(This article belongs to the Special Issue Phytohormones 2020)

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71 pages, 1595 KiB

Open AccessReview

Applications of Cytokinins in Horticultural Fruit Crops: Trends and Future Prospects

by Adeyemi O. Aremu, Olaniyi A. Fawole, Nokwanda P. Makunga, Nqobile A. Masondo, Mack Moyo, Nana M. D. Buthelezi, Stephen O. Amoo, Lukáš Spíchal and Karel Doležal

Biomolecules 2020, 10(9), 1222; https://doi.org/10.3390/biom10091222 - 22 Aug 2020

Cited by 21 | Viewed by 11659

Abstract

Cytokinins (CKs) are a chemically diverse class of plant growth regulators, exhibiting wide-ranging actions on plant growth and development, hence their exploitation in agriculture for crop improvement and management. Their coordinated regulatory effects and cross-talk interactions with other phytohormones and signaling networks are highly sophisticated, eliciting and controlling varied biological processes at the cellular to organismal levels. In this review, we briefly introduce the mode of action and general molecular biological effects of naturally occurring CKs before highlighting the great variability in the response of fruit crops to CK-based innovations. We present a comprehensive compilation of research linked to the application of CKs in non-model crop species in different phases of fruit production and management. By doing so, it is clear that the effects of CKs on fruit set, development, maturation, and ripening are not necessarily generic, even for cultivars within the same species, illustrating the magnitude of yet unknown intricate biochemical and genetic mechanisms regulating these processes in different fruit crops. Current approaches using genomic-to-metabolomic analysis are providing new insights into the in planta mechanisms of CKs, pinpointing the underlying CK-derived actions that may serve as potential targets for improving crop-specific traits and the development of new solutions for the preharvest and postharvest management of fruit crops. Where information is available, CK molecular biology is discussed in the context of its present and future implications in the applications of CKs to fruits of horticultural significance. Full article

(This article belongs to the Special Issue Phytohormones 2020)

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22 pages, 1903 KiB

Open AccessReview

Ethylene: A Master Regulator of Salinity Stress Tolerance in Plants

by Riyazuddin Riyazuddin, Radhika Verma, Kalpita Singh, Nisha Nisha, Monika Keisham, Kaushal Kumar Bhati, Sun Tae Kim and Ravi Gupta

Biomolecules 2020, 10(6), 959; https://doi.org/10.3390/biom10060959 - 25 Jun 2020

Cited by 124 | Viewed by 10689

Abstract

Salinity stress is one of the major threats to agricultural productivity across the globe. Research in the past three decades, therefore, has focused on analyzing the effects of salinity stress on the plants. Evidence gathered over the years supports the role of ethylene as a key regulator of salinity stress tolerance in plants. This gaseous plant hormone regulates many vital cellular processes starting from seed germination to photosynthesis for maintaining the plants’ growth and yield under salinity stress. Ethylene modulates salinity stress responses largely via maintaining the homeostasis of Na⁺/K⁺, nutrients, and reactive oxygen species (ROS) by inducing antioxidant defense in addition to elevating the assimilation of nitrates and sulfates. Moreover, a cross-talk of ethylene signaling with other phytohormones has also been observed, which collectively regulate the salinity stress responses in plants. The present review provides a comprehensive update on the prospects of ethylene signaling and its cross-talk with other phytohormones to regulate salinity stress tolerance in plants. Full article

(This article belongs to the Special Issue Phytohormones 2020)

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