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Authors: Lei Wang, Mohsin Tanveer, Hongling Wang and Marino B. Arnao.
Journal of Pineal Research (2024)
Abstract: "Seed germination (SG) is the first stage in a plant's life and has an immense importance in sustaining crop production. Abiotic stresses reduce SG by increasing the deterioration of seed quality, and reducing germination potential, and seed vigor. Thus, to achieve a sustainable level of crop yield, it is important to improve SG under abiotic stress conditions. Melatonin (MEL) is an important biomolecule that interplays in developmental processes and regulates many adaptive responses in plants, especially under abiotic stresses. Thus, this review specifically summarizes and discusses the mechanistic basis of MEL-mediated SG under abiotic stresses. MEL regulates SG by regulating some stress-specific responses and some common responses. For instance, MEL induced stress specific responses include the regulation of ionic homeostasis, and hydrolysis of storage proteins under salinity stress, regulation of C-repeat binding factors signaling under cold stress, starch metabolism under high temperature and heavy metal stress, and activation of aquaporins and accumulation of osmolytes under drought stress. On other hand, MEL mediated regulation of gibberellins biosynthesis and abscisic acid catabolism, redox homeostasis, and Ca2+ signaling are amongst the common responses. Nonetheless factors such as endogenous MEL contents, plant species, and growth conditions also influence above-mentioned responses. In conclusion, MEL regulates SG under abiotic stress conditions by interacting with different physiological mechanisms."
Authors: Takuya Furumoto, Shohei Yamaoka, Takayuki Kohchi, Hiroyasu Motose and Taku Takahashi.
Plant and Cell Physiology (2024)
Abstract: "Thermospermine suppresses auxin-inducible xylem differentiation, whereas its structural isomer, spermine, is involved in stress responses in angiosperms. The thermospermine synthase, ACAULIS5 (ACL5), is conserved from algae to land plants, but its physiological functions remain elusive in non-vascular plants. Here, we focused on MpACL5, a gene in the liverwort Marchantia polymorpha, that rescued the dwarf phenotype of the acl5 mutant in Arabidopsis. In the Mpacl5 mutants generated by genome editing, severe growth retardation was observed in the vegetative organ, thallus, and the sexual reproductive organ, gametangiophore. The mutant gametangiophores exhibited remarkable morphological defects such as short stalks, fasciation, and indeterminate growth. Two gametangiophores fused together and new gametangiophores were often initiated from the old ones. Furthermore, Mpacl5 showed altered responses to heat and salt stresses. Given the absence of spermine in bryophytes, these results suggest that thermospermine has a dual primordial function in organ development and stress responses in M. polymorpha. The stress response function may have eventually been assigned to spermine during land plant evolution."
Authors: Ming-Che James Liu, Fang-Ling Jessica Yeh, Robert Yvon, Kelly Simpson, Samuel Jordan, James Chambers, Hen-Ming Wu and Alice Y. Cheung.
Cell (2024)
Editor's view: In deciphering the global signaling capacity of FERONIA receptor kinase, Liu, Yeh, et al. discovered an extracellular phase separation process driven by FERONIA peptide ligand RALF-cell wall polysaccharide pectin interaction, which leads to cognate and non-cognate receptor clustering and promiscuous endocytosis as a coping mechanism in response to environmental stressors.
Highlights: • Cell surface pectin-RALF1 phase separation recruits FERONIA-LLG1 into condensates • RALF induces FERONIA-LLG1-dependent promiscuous receptor clustering and endocytosis • RALF1-pectin molecular condensates function as surface sensors for stress signals • FERONIA-LLG1-mediated global endocytosis ensures plant resilience under stress
Abstract: "The FERONIA (FER)-LLG1 co-receptor and its peptide ligand RALF regulate myriad processes for plant growth and survival. Focusing on signal-induced cell surface responses, we discovered that intrinsically disordered RALF triggers clustering and endocytosis of its cognate receptors and FER- and LLG1-dependent endocytosis of non-cognate regulators of diverse processes, thus capable of broadly impacting downstream responses. RALF, however, remains extracellular. We demonstrate that RALF binds the cell wall polysaccharide pectin. They phase separate and recruit FER and LLG1 into pectin-RALF-FER-LLG1 condensates to initiate RALF-triggered cell surface responses. We show further that two frequently encountered environmental challenges, elevated salt and temperature, trigger RALF-pectin phase separation, promiscuous receptor clustering and massive endocytosis, and that this process is crucial for recovery from stress-induced growth attenuation. Our results support that RALF-pectin phase separation mediates an exoskeletal mechanism to broadly activate FER-LLG1-dependent cell surface responses to mediate the global role of FER in plant growth and survival."
Authors: Ming Wu, Elshan Musazade, Xiao Yang, Le Yin, Zizhu Zhao, Yu Zhang, Jingmei Lu and Liquan Guo.
Journal of Agricultural and Food Chemistry (2023)
Abstract: "Plants actively develop intricate regulatory mechanisms to counteract the harmful effects of environmental stresses. The ubiquitin–proteasome pathway, a crucial mechanism, employs E3 ligases (E3s) to facilitate the conjugation of ubiquitin to specific target substrates, effectively marking them for proteolytic degradation. E3s play critical roles in many biological processes, including phytohormonal signaling and adaptation to environmental stresses. Arabidopsis Toxicos en Levadura (ATL) proteins, belonging to a subfamily of RING-H2 E3s, actively modulate diverse physiological processes and plant responses to environmental stresses. Despite studies on the functions of certain ATL family members in rice and Arabidopsis, most ATLs still need more comprehensive study. This review presents an overview of the ubiquitin–proteasome system (UPS), specifically focusing on the pivotal role of E3s and associated enzymes in plant development and environmental adaptation. Our study seeks to unveil the active modulation of plant responses to environmental stresses by E3s and ATLs, emphasizing the significance of ATLs within this intricate process. By emphasizing the importance of studying the roles of E3s and ATLs, our review contributes to developing more resilient plant varieties and promoting sustainable agricultural practices while establishing a research roadmap for the future."
Authors: Tanya Singh, Nikita Bisht, Mohd Mogees Ansari and Puneet Singh Chauhan.
Plant Physiology and Biochemistry (2024)
Highlights • Plant roots play an essential role in adapting to environmental cues. • Coordinated cellular processes are driven by ROS and plant hormones. • Bidirectional interaction of ROS and hormones shapes plant root development. • ROS-hormone interplay offers agricultural potential to enhance plant stress resilience.
Abstract: "Root system architecture, encompassing lateral roots and root hairs, plays a vital in overall plant growth and stress tolerance. Reactive oxygen species (ROS) and plant hormones intricately regulate root growth and development, serving as signaling molecules that govern processes such as cell proliferation and differentiation. Manipulating the interplay between ROS and hormones has the potential to enhance nutrient absorption, stress tolerance, and agricultural productivity. In this review, we delve into how studying these processes provides insights into how plants respond to environmental changes and optimize growth patterns to better control cellular processes and stress responses in crops. We discuss various factors and complex signaling networks that may exist among ROS and phytohormones during root development. Additionally, the review highlights possible role of reactive nitrogen species (RNS) in ROS-phytohormone interactions and in shaping root system architecture according to environmental cues."
Authors: Ze Liu, Hengrui Dai, Jinjiang Hao, Rongrong Li, Xiaojun Pu, Miao Guan and Qi Chen.
Stress Biology (2023)
Abstract: "Seed germination is a complex process regulated by internal and external factors. Melatonin (N-acetyl-5-methoxytryptamine) is a ubiquitous signaling molecule, playing an important role in regulating seed germination under normal and stressful conditions. In this review, we aim to provide a comprehensive overview on melatonin's effects on seed germination on the basis of existing literature. Under normal conditions, exogenous high levels of melatonin can suppress or delay seed germination, suggesting that melatonin may play a role in maintaining seed dormancy and preventing premature germination. Conversely, under stressful conditions (e.g., high salinity, drought, and extreme temperatures), melatonin has been found to accelerate seed germination. Melatonin can modulate the expression of genes involved in ABA and GA metabolism, thereby influencing the balance of these hormones and affecting the ABA/GA ratio. Melatonin has been shown to modulate ROS accumulation and nutrient mobilization, which can impact the germination process. In conclusion, melatonin can inhibit germination under normal conditions while promoting germination under stressful conditions via regulating the ABA/GA ratios, ROS levels, and metabolic enzyme activity. Further research in this area will deepen our understanding of melatonin's intricate role in seed germination and may contribute to the development of improved seed treatments and agricultural practices."
Authors: Yun-Jing Bao, Jia-Xu Chen, Youjun Zhang, Alisdair R. Fernie, Jianhua Zhang, Bao-Xing Huang, Fu-Yuan Zhu and Fu-Liang Cao.
Advanced Agrochem (2024)
Highlights: • This review addresses the multiple roles served by JA-involved regulatory networks in different woody species, which have similar properties and differential regulation within their herbaceous counterparts, especially focusing on developmental growth. • The potential role of AS a regulatory mechanism of JA modulation, which is concerned with plant development and stress responses. The utilization of proteogenomic analysis would further advance our standing of JA-mediated AS regulation and elucidate the specific mechanisms in woody plants.
Abstract: "Jasmonic acid is a crucial phytohormone that plays a pivotal role, serving as a regulator to balancing plant development and resistance. However, there are analogous and distinctive characteristics exhibited in JA biosynthesis, perception, and signal transduction pathways in both herbaceous and woody plants. Moreover, the majority of research subjects have predominantly focused on the function of JA in model or herbaceous plants. Consequently, there is a significant paucity of studies investigating JA regulation networks in woody plants, particularly concerning post-transcriptional regulatory events such as alternative splicing (AS). This review article aims to conduct a comprehensive summary of advancements that JA signals regulate plant development across various woody species, comparing the analogous features and regulatory differences to herbaceous counterparts. In addition, we summarized the involvement of AS events including splicing factor (SF) and transcripts in the JA regulatory network, highlighting the effectiveness of high-throughput proteogenomic methods. A better understanding of the JA signaling pathway in woody plants has pivotal implications for forestry production, including optimizing plant management and enhancing secondary metabolite production."
Authors: Ariel Cerda and José M. Alvarez.
New Phytologist (2024)
Abstract: "Drought and the availability of nitrate, the predominant source of nitrogen (N) in agriculture, are major factors limiting plant growth and crop productivity. The dissection of the transcriptional networks' components integrating drought stress and nitrate responses provides valuable insights into how plants effectively balance stress response with growth programs. Recent evidence in Arabidopsis thaliana indicates that transcription factors (TFs) involved in abscisic acid (ABA) signaling affect N metabolism and nitrate responses, and reciprocally, components of nitrate signaling might affect ABA and drought gene responses. Advances in understanding regulatory circuits of nitrate and drought crosstalk in plant tissues empower targeted genetic modifications to enhance plant development and stress resistance, critical traits for optimizing crop yield and promoting sustainable agriculture."
Authors: Oded Pri-Tal, Yufei Sun, Armin Dadras, Janine M. R. Fürst-Jansen, Gil Zimran, Daphna Michaeli, Akila Wijerathna-Yapa, Michal Shpilman, Ebe Merilo, Dmitry Yarmolinsky, Idan Efroni, Jan de Vries, Hannes Kollist and Assaf Mosquna.
New Phytologist (2024)
Abstract: "Abscisic acid (ABA) is best known for regulating the responses to abiotic stressors. Thus, applications of ABA signaling pathways are considered promising targets for securing yield under stress. ABA levels rise in response to abiotic stress, mounting physiological and metabolic responses that promote plant survival under unfavorable conditions. ABA elicits its effects by binding to a family of soluble receptors found in monomeric and dimeric states, differing in their affinity to ABA and co-receptors. However, the in vivo significance of the biochemical differences between these receptors remains unclear. We took a gain-of-function approach to study receptor-specific functionality. First, we introduced activating mutations that enforce active ABA-bound receptor conformation. We then transformed Arabidopsis ABA-deficient mutants with the constitutive receptors and monitored suppression of the ABA deficiency phenotype. Our findings suggest that PYL4 and PYL5, monomeric ABA receptors, have differential activity in regulating transpiration and transcription of ABA biosynthesis and stress response genes. Through genetic and metabolic data, we demonstrate that PYR1, but not PYL5, is sufficient to activate the ABA positive feedback mechanism. We propose that ABA signaling – from perception to response – flows differently when triggered by different PYLs, due to tissue and transcription barriers, thus resulting in distinct circuitries."
Authors: Quy Thi Cam Nguyen and Jungmook Kim.
Plant Signaling & Behavior (2023)
Abstract: "Leucine-rich repeat-receptor kinases (LRR-RKs) perceive various endogenous peptide hormones that control plant growth and development. However, the majority of corresponding ligands and their direct ligand-binding receptors have not been identified yet. A recent study demonstrated that three LRR-RK PLANT PEPTIDE CONTAINING SULFATED TYROSINE RECEPTORS (PSYRs) act as ligand-receptors of the PSY family peptides that mediate the trade-off between the optimal plant growth and stress tolerance responses. The genetic, biochemical, and transcriptome analyses suggested that PSYR1, PSYR2, and PSYR3 function as negative regulators of plant growth in the absence of PSY peptides and induce stress tolerance responses, whereas the PSY family peptides repress PSYR signaling, allowing plant growth. This trade-off mechanism between plant growth and stress responses mediated by the PSY–PSYR signaling module allows plants to survive under ever changing environmental stresses."
Authors: Takuya Yoshida and Alisdair R. Fernie
Journal of Experimental Botany (2024)
Abstract: "Phytohormones are essential signaling molecules globally regulating many processes of plants, including their growth, development and stress responses. The promotion of growth and the enhancement of stress resistance have to be balanced, especially under adverse conditions such as drought stress, because of limited resources. Plants cope with drought stress via various strategies, including the transcriptional regulation of stress-responsive genes and the adjustment of metabolism, and phytohormones play roles in these processes. However, besides abscisic acid (ABA) is an important signal under drought, less attention has been paid to other phytohormones. In this review, we summarize progress in the understanding of phytohormone-regulated primary metabolism under water-limited conditions, especially in Arabidopsis thaliana, and highlight recent findings concerning the amino acids associated with ABA metabolism and signaling. We also discuss how phytohormones function antagonistically and synergistically in order to balance growth and stress responses."
Authors: Sompop Pinit, Lalichat Ariyakulkiat and Juthamas Chaiwanon.
Scientific Reports (2023)
Abstract: "Plant-derived smoke has been shown to promote plant growth and seed germination, but its roles and mechanisms in response to nutrient deficiency stress remain unclear. Plants respond to phosphorus (P) deficiency by undergoing morphological, physiological, and transcriptional changes in order to improve nutrient uptake efficiency. Here, we showed that rice straw-derived smoke water could promote root growth in rice (Oryza sativa cv. Nipponbare) grown under P-sufficient and P-deficient conditions. Transcriptome analysis of the root tissues identified 1309 genes up-regulated and 1311 genes down-regulated by smoke water under P-deficient conditions. The GO terms ‘glutathione transferase activity’ and ‘photosynthesis—light reaction’ were found to be significantly enriched among the genes that were up- and down-regulated by smoke water, respectively. Biochemical analysis showed that smoke water reduced P-deficient-induced accumulation of H2O2 and malondialdehyde (MDA), a lipid peroxidation marker, reduced sucrose contents, but increased Fe accumulation. Furthermore, smoke water suppressed the expression of strigolactone biosynthesis genes, which were strongly induced by P deficiency as an adaptive strategy to improve root P uptake. These results revealed a potential mechanism by which smoke water promotes root growth and interacts with P deficiency-induced transcriptional regulation to mitigate P deficiency stress in rice."
Authors: Gustavo Ravelo-Ortega, Karen M. García-Valle, Ramón Pelagio-Flores and José López-Bucio.
In book: Melatonin: Role in Plant Signaling, Growth and Stress Tolerance (2023)
Abstract: "In recent years, knowledge has been gained into the mechanisms of action of melatonin in plants and its regulation of morphogenesis. Melatonin accumulates in several organs, such as the root, stem, and leaves, and can be transported from the major site of synthesis in leaves to distant tissues through the vascular bundles, where it affects cell signaling in crosstalk with major phytohormones. The structural similarity of melatonin with indole-3-acetic acid (IAA) led some authors to suggest a potential auxinic effect in plant signal transduction, particularly root branching and stem elongation. However, its physiological roles throughout the life cycle of plants did not support an auxinic role, but in contrast suggest independent mechanisms of action for each molecule, in agreement with the recent discovery of the melatonin receptor CAND2 that differs from the auxin receptors. This chapter describes the recent roles of melatonin in seed germination, root architecture, shoot development, reproduction, and senescence, and the genes and proteins targeted by melatonin signaling. The function of melatonin in these processes goes beyond its function as an antioxidant, and their possible applications represent a valuable input to optimize plant productivity and confer protection against stressing growth conditions."
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Authors: Xin Zhang, Yongchen Yu, Jin Zhang, Xiaona Qian, Xiwang Li and Xiaoling Sun.
International Journal of Molecular Sciences (2024)
Abstract: "Tea plants have to adapt to frequently challenging environments due to their sessile lifestyle and perennial evergreen nature. Jasmonates regulate not only tea plants’ responses to biotic stresses, including herbivore attack and pathogen infection, but also tolerance to abiotic stresses, such as extreme weather conditions and osmotic stress. In this review, we summarize recent progress about jasmonic acid (JA) biosynthesis and signaling pathways, as well as the underlying mechanisms mediated by jasmonates in tea plants in responses to biotic stresses and abiotic stresses. This review provides a reference for future research on the JA signaling pathway in terms of its regulation against various stresses of tea plants. Due to the lack of a genetic transformation system, the JA pathway of tea plants is still in the preliminary stages. It is necessary to perform further efforts to identify new components involved in the JA regulatory pathway through the combination of genetic and biochemical methods."
Authors: Hikaru Sato, Junya Mizoi, Kazuo Shinozaki and Kazuko Yamaguchi-Shinozaki.
The Plant Journal (2024)
Significance Statement: In this review, we explain how plants respond to drought, heat, and their combined stress at both physiological and molecular levels. Additionally, we summarize novel resilience mechanisms revealed through natural variations and discuss strategies for developing crops resilient to the increasing dry and hot conditions resulting from climate change.
Abstract: "Global climate change is predicted to result in increased yield losses of agricultural crops caused by environmental conditions. In particular, heat and drought stress are major factors that negatively affect plant development and reproduction, and previous studies have revealed how these stresses induce plant responses at physiological and molecular levels. Here, we provide a comprehensive overview of current knowledge concerning how drought, heat, and combinations of these stress conditions affect the status of plants, including crops, by affecting factors such as stomatal conductance, photosynthetic activity, cellular oxidative conditions, metabolomic profiles, and molecular signaling mechanisms. We further discuss stress-responsive regulatory factors such as transcription factors and signaling factors, which play critical roles in adaptation to both drought and heat stress conditions and potentially function as ‘hubs’ in drought and/or heat stress responses. Additionally, we present recent findings based on forward genetic approaches that reveal natural variations in agricultural crops that play critical roles in agricultural traits under drought and/or heat conditions. Finally, we provide an overview of the application of decades of study results to actual agricultural fields as a strategy to increase drought and/or heat stress tolerance. This review summarizes our current understanding of plant responses to drought, heat, and combinations of these stress conditions."
Authors: Hayet Houmani and Francisco J. Corpas.
Plant Physiology and Biochemistry (2024)
Highlights • Mineral nutrients are determinant factors for plant growth and development. • Some minerals have signaling properties and can mediate a stress response. • Nutrients such as Ca2+, K+, N, or Fe interact with other signaling molecules (hormones, NO, H2O2 or H2S) to exert their signaling function.
Abstract: "Plant cells are in constant communication to coordinate development processes and environmental reactions. Under stressful conditions, such communication allows the plant cells to adjust their activities and development. This is due to intercellular signaling events which involve several components. In plant development, cell-to-cell signaling is ensured by mobile signals hormones, hydrogen peroxide (H2O2), nitric oxide (NO), or hydrogen sulfide (H2S), as well as several transcription factors and small RNAs. Mineral nutrients, including macro and microelements, are determinant factors for plant growth and development and are, currently, recognized as potential signal molecules. This review aims to highlight the role of nutrients, particularly calcium, potassium, magnesium, nitrogen, phosphorus, and iron as signaling components with special attention to the mechanism of response against stress conditions."
Authors: Sampurna Kashyap, Niraj Agarwala and Ramanjulu Sunkar.
Plant Science (2024)
Highlights • Like animals, plants can also memorize past threats and respond robustly to future episodes of the same or similar circumstances. • Stress memory might be generated due to hypersensitive immune responses, epigenetic changes, modulation in hormonal signalling, etc. • The ingenious adaptability of the crop wild relatives (CWRs) in challenging climatic conditions might be due to their peculiar memory functions. • Exploitation of CWRs memory traits may help crop breeders develop more resilient and climate-smart crops. • The ability of plants to modulate root exudation patterns in response to stress conditions can be a component of plant memory.
Abstract: "Being sessile, plants encounter a variety of biotic and abiotic threats in their life cycle. To minimize the damages caused by such threats, plants have acquired sophisticated response mechanisms. One major such response includes memorizing the encountered stimuli in the form of a metabolite, hormone, protein, or epigenetic marks. All of these individually as well as together, facilitate effective transcriptional and post-transcriptional responses upon encountering the stress episode for a second time during the life cycle and in some instances even in the future generations. This review attempts to highlight the recent advances in the area of plant memory. A detailed understanding of plant memory has the potential to offer solutions for developing climate-resilient crops for sustainable agriculture."
Authors: Pan Luo,Ting-Ting Li, Wei-Ming Shi, Qi Ma and Dong-Wei Di.
Plants (2024)
Abstract: "The precise control of free auxin (indole-3-acetic acid, IAA) gradient, which is orchestrated by biosynthesis, conjugation, degradation, hydrolyzation, and transport, is critical for all aspects of plant growth and development. Of these, the GRETCHEN HAGEN 3 (GH3) acyl acid amido synthetase family, pivotal in conjugating IAA with amino acids, has garnered significant interest. Recent advances in understanding GH3-dependent IAA conjugation have positioned GH3 functional elucidation as a hot topic of research. This review aims to consolidate and discuss recent findings on (i) the enzymatic mechanisms driving GH3 activity, (ii) the influence of chemical inhibitor on GH3 function, and (iii) the transcriptional regulation of GH3 and its impact on plant development and stress response. Additionally, we explore the distinct biological functions attributed to IAA-amino acid conjugates."
Authors: Manvi Sharma and Petra Marhava.
Current Opinion in Plant Biology (2023)
Abstract: "Plants have evolved robust adaptive mechanisms to withstand the ever-changing environment. Tightly regulated distribution of the hormone auxin throughout the plant body controls an impressive variety of developmental processes that tailor plant growth and morphology to environmental conditions. The proper flow and directionality of auxin between cells is mainly governed by asymmetrically localized efflux carriers – PINs – ensuring proper coordination of developmental processes in plants. Discerning the molecular players and cellular dynamics involved in the establishment and maintenance of PINs in specific membrane domains, as well as their ability to readjust in response to abiotic stressors is essential for understanding how plants balance adaptability and stability. While much is known about how PINs get polarized, there is still limited knowledge about how abiotic stresses alter PIN polarity by acting on these systems. In this review, we focus on the current understanding of mechanisms involved in (re)establishing and maintaining PIN polarity under abiotic stresses."
Authors: Jong Hee Im, Seungmin Son, Won-Chan Kim, Kihwan Kim, Nobutaka Mitsuda, Jae-Heung Ko and Kyung-Hwan Han.
The Plant Journal (2024)
Abstract: "Formation of secondary cell wall (SCW) is tightly regulated spatiotemporally by various developmental and environmental signals. Successful fine-tuning of the trade-off between SCW biosynthesis and stress responses requires a better understanding of how plant growth is regulated under environmental stress conditions. However, the current understanding of the interplay between environmental signaling and SCW formation is limited. The lipid-derived plant hormone jasmonate (JA) and its derivatives are important signaling components involved in various physiological processes including plant growth, development, and abiotic/biotic stress responses. Recent studies suggest that JA is involved in SCW formation but the signaling pathway has not been studied for how JA regulates SCW formation. We tested this hypothesis using the transcription factor MYB46, a master switch for SCW biosynthesis, and JA treatments. Both the transcript and protein levels of MYB46, a master switch for SCW formation, were significantly increased by JA treatment, resulting in the upregulation of SCW biosynthesis. We then show that this JA-induced upregulation of MYB46 is mediated by MYC2, a central regulator of JA signaling, which binds to the promoter of MYB46. We conclude that this MYC2-MYB46 module is a key component of the plant response to JA in SCW formation."
Authors: Jian-Jun Tao, Cui-Cui Yin, Yang Zhou, Yi-Hua Huang, Shou-Yi Chen and Jin-Song Zhang.
Environmental and Experimental Botany (2024)
Highlights: • Universal and divergent functions of ethylene in different crops under salinity. • The opposite role of ethylene signaling in rice compared to some other crops. • The dual roles of ethylene being a stress signal and a stress substance.
Abstract: "Soil salinization severely hinders plant growth and decreases crop yield, and is increasingly an obstacle for the sustainability of agriculture. As a stress hormone, ethylene is known to function as a signal molecule to coordinate plant growth and stress response in the dicotyledonous model plant Arabidopsis. However, the roles of ethylene in most crop plants under salinity have received less attention, and underlying mechanisms are still undefined. According to reported results, the functions of ethylene as a stress signal in some crop species like the semiaquatic monocotyledonous plant rice turn out to be much different. Moreover, there exist some contradictions between ethylene production and signaling in salt response. Therefore, in this review, besides making a summary of the universal roles, we also focus on the divergent roles of ethylene under salinity in rice and some other crop species, in terms of ethylene biosynthesis and signal transduction. In addition, the discrepancies between ethylene production and signaling in salt response are discussed."
Authors: Shiyi Xie, Hongbing Luo, Wei Huang, Weiwei Jin and Zhaobin Dong.
International Journal of Plant Biology (2024)
Abstract: "Maize (Zea mays) cultivation is strongly affected by both abiotic and biotic stress, leading to reduced growth and productivity. It has recently become clear that regulators of plant stress responses, including the phytohormones abscisic acid (ABA), ethylene (ET), and jasmonic acid (JA), together with reactive oxygen species (ROS), shape plant growth and development. Beyond their well-established functions in stress responses, these molecules play crucial roles in balancing growth and defense, which must be finely tuned to achieve high yields in crops while maintaining some level of defense. In this review, we provide an in-depth analysis of recent research on the developmental functions of stress regulators, focusing specifically on maize. By unraveling the contributions of these regulators to maize development, we present new avenues for enhancing maize cultivation and growth while highlighting the potential risks associated with manipulating stress regulators to enhance grain yields in the face of environmental challenges."
Authors: Zhang You, Shiyuan Guo, Qiao Li, Yanjun Fang, Panpan Huang, Chuanfeng Ju and Cun Wang.
Nature Communications (2023)
Editor's view: ABA signaling and Ca2+ signaling regulatory networks are crucial for how plants respond to drought stress. Here, the authors reported that the functional module of the CBL1/9-CIPK1-PYLs regulatory network plays a negative role in ABA signaling and its response to drought stress.
Abstract: "The stress hormone, Abscisic acid (ABA), is crucial for plants to respond to changes in their environment. It triggers changes in cytoplasmic Ca2+ levels, which activate plant responses to external stresses. However, how Ca2+ sensing and signaling feeds back into ABA signaling is not well understood. Here we reveal a calcium sensing module that negatively regulates drought stress via modulating ABA receptor PYLs. Mutants cbl1/9 and cipk1 exhibit hypersensitivity to ABA and drought resilience. Furthermore, CIPK1 is shown to interact with and phosphorylate 7 of 14 ABA receptors at the evolutionarily conserved site corresponding to PYL4 Ser129, thereby suppressing their activities and promoting PP2C activities under normal conditions. Under drought stress, ABA impedes PYLs phosphorylation by CIPK1 to respond to ABA signaling and survive in unfavorable environment. These findings provide insights into a previously unknown negative regulatory mechanism of the ABA signaling pathway, which is mediated by CBL1/9-CIPK1-PYLs, resulting in plants that are more sensitive to drought stress. This discovery expands our knowledge about the interplay between Ca2+ signaling and ABA signaling."
Authors: Omid Karami, Hanna de Jong, Victor J. Somovilla, Beatriz Villanueva Acosta, Aldo Bryan Sugiarta, Marvin Ham, Azadeh Khadem, Tom Wennekes and Remko Offringa.
The Plant Journal (2023)
Significance Statement: The synthetic auxin 2,4-D effectively induces somatic embryogenesis in Arabidopsis thaliana, and the stress-related effects triggered by 2,4-D are considered important for this process. By testing a library of forty 2,4-D analogues and using auxin receptor mutants we show that auxin signalling is required for both stress and somatic embryogenesis induction by 2,4-D.
Abstract: "2,4-dichlorophenoxyacetic acid (2,4-D) is a synthetic analogue of the plant hormone auxin that is commonly used in many in vitro plant regeneration systems, such as somatic embryogenesis (SE). Its effectiveness in inducing SE, compared to the natural auxin indole-3-acetic acid (IAA), has been attributed to the stress triggered by this compound rather than its auxinic activity. However, this hypothesis has never been thoroughly tested. Here we used a library of forty 2,4-D analogues to test the structure–activity relationship with respect to the capacity to induce SE and auxinic activity in Arabidopsis thaliana. Four analogues induced SE as effectively as 2,4-D and 13 analogues induced SE but were less effective. Based on root growth inhibition and auxin response reporter expression, the 2,4-D analogues were classified into different groups, ranging from very active to not active auxin analogues. A halogen at the 4-position of the aromatic ring was important for auxinic activity, whereas a halogen at the 3-position resulted in reduced activity. Moreover, a small substitution at the carboxylate chain was tolerated, as was extending the carboxylate chain with an even number of carbons. The auxinic activity of most 2,4-D analogues was consistent with their simulated TIR1-Aux/IAA coreceptor binding characteristics. A strong correlation was observed between SE induction efficiency and auxinic activity, which is in line with our observation that 2,4-D-induced SE and stress both require TIR1/AFB auxin co-receptor function. Our data indicate that the stress-related effects triggered by 2,4-D and considered important for SE induction are downstream of auxin signalling."
Authors: Aung Htay Naing, Sangcheol Baek, Jova Riza Campol, Hyunhee Kang and Chang Kil Kim.
Plant Physiology and Biochemistry (2023)
Highlights: • Abiotic stress-induced growth inhibition in petunia was linked to ethylene production. • Loss of ACO4 in petunia reduced stress-induced ethylene and ROS. • ACO4 acts as a negative regulator of stress tolerance.
Abstract: "To investigate the role of ethylene (ET) in abiotic stress tolerance in petunia cv. ‘Mirage Rose’, petunia plants in which the ET biosynthesis gene 1-aminocyclopropane-1-carboxylic acid oxidase 4 (ACO4) was knocked out (phaco4 mutants) and wild-type (WT) plants were exposed to heat and drought conditions. Loss of function of ACO4 significantly delayed leaf senescence and chlorosis under heat and drought stress by maintaining the SPAD values and the relative water content, indicating a greater stress tolerance of phaco4 mutants than that of WT plants. This tolerance was related to the lower ET and reactive oxygen species levels in the mutants than in WT plants. Furthermore, the stress-induced expression of genes related to ET signal transduction, antioxidant and proline activities, heat response, and biosynthesis of abscisic acid was higher in the mutants than in WT plants, indicating a greater stress tolerance in the former than in the latter. These results demonstrate the deleterious effects of stress-induced ET on plant growth and provide a better physiological and molecular understanding of the role of stress ET in the abiotic stress response of petunia. Because the loss of function of ACO4 in petunia improved stress tolerance, we suggest that ACO4 plays a vital role in stress-induced leaf senescence and acts as a negative regulator of abiotic stress tolerance."
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