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Authors: Xiaoyun Wang, Meng Cao, Hongxin Li, Ying Liu, Shuangxi Fan, Na Zhang and Yangdong Guo.
Horticultural Plant Journal (2024)
Abstract: "Melatonin is a conserved pleiotropic molecule in animals and plants. Melatonin is involved in many development processes and stress responses; thus, exploring its function in plants, particularly in horticultural plants, has become a rapidly developing field. Many studies have revealed that phytomelatonin acts as a plant biostimulant and increase its tolerance to various abiotic stressors, including extreme temperature, drought, osmotic disturbance, heavy metals, and ultraviolet (UV). Melatonin appears to have roles in the scavenging of reactive oxygen species (ROS) and other free radicals, affecting the primary and secondary metabolism of plants, regulating the transcripts of stress-related enzymes and transcription factors, and crosstalk with other hormones under different environmental conditions. This pleiotropy makes phytomelatonin an attractive regulator to improve resistance to abiotic stress in plants. The recent discovery of the potential phytomelatonin receptor CAND2/PMTR1 and the proposition of putative models related to the phytomelatonin signaling pathways makes phytomelatonin a new plant hormone. Based on relevant studies from our laboratory, this review summarizes the phytomelatonin biosynthetic and metabolic pathways in plants and the latest research progress on phytomelatonin in abiotic stress of horticultural plants. This study will provide a reference for elucidating the regulatory mechanism of phytomelatonin affecting the resistance to abiotic stress in plants."
Authors: María Ángeles Peláez-Vico, Yosef Fichman, Sara I. Zandalinas, Christine H. Foyer and Ron Mittler.
Current Opinion in Plant Biology (2024)
Highlights • The interplay between ROS and redox is deeply rooted in the biology of many different organisms. • The ROS/redox state of one cell can be transmitted to other cells generating a chain of cell-to-cell signaling events. • ROS/redox signaling is linked with other signal transduction pathways in cells controlling systemic signaling/acclimation. • Cell-to-cell transfer of ROS/redox states between different organisms links environmental stress to human health. • Hydrogen peroxide is a universal cell-to-cell signal and possibly one of the first stress hormones to emerge on Earth.
Abstract: "The interplay between reactive oxygen species (ROS) and the redox state of cells is deeply rooted in the biology of almost all organisms, regulating development, growth, and responses to the environment. Recent studies revealed that the ROS levels and redox state of one cell can be transmitted, as an information ‘state’ or ‘currency’, to other cells and spread by cell-to-cell communication within an entire community of cells or an organism. Here, we discuss the different pathways that mediate cell-to-cell signaling in plants, their hierarchy, and the different mechanisms that transmit ROS/redox signaling between different cells. We further hypothesize that ROS/redox signaling between different organisms could play a key role within the ‘one world’ principle, impacting human health and our future."
Authors: Mervin Chun-Yi Ang, Jolly Madathiparambil Saju, Thomas K. Porter, Sayyid Mohaideen, Sreelatha Sarangapani, Duc Thinh Khong, Song Wang, Jianqiao Cui, Suh In Loh, Gajendra Pratap Singh, Nam-Hai Chua, Michael S. Strano and Rajani Sarojam.
Nature Communications (2024)
Editor's view: Upon stress, plants activate a signaling cascade leading to resistance or stress adaptation. Here, Ang & Saju et al. use sensor multiplexing to elucidate the interplay between H2O2 and SA signaling as plants mount stress-specific defense responses.
Abstract: "Increased exposure to environmental stresses due to climate change have adversely affected plant growth and productivity. Upon stress, plants activate a signaling cascade, involving multiple molecules like H2O2, and plant hormones such as salicylic acid (SA) leading to resistance or stress adaptation. However, the temporal ordering and composition of the resulting cascade remains largely unknown. In this study we developed a nanosensor for SA and multiplexed it with H2O2 nanosensor for simultaneous monitoring of stress-induced H2O2 and SA signals when Brassica rapa subsp. chinensis (Pak choi) plants were subjected to distinct stress treatments, namely light, heat, pathogen stress and mechanical wounding. Nanosensors reported distinct dynamics and temporal wave characteristics of H2O2 and SA generation for each stress. Based on these temporal insights, we have formulated a biochemical kinetic model that suggests the early H2O2 waveform encodes information specific to each stress type. These results demonstrate that sensor multiplexing can reveal stress signaling mechanisms in plants, aiding in developing climate-resilient crops and pre-symptomatic stress diagnoses."
Authors: Mingjuan Zhai, Yating Chen, Xiaowu Pan, Ying Chen, Jiahao Zhou, Xiaodan Jiang, Zhijin Zhang, Guiqing Xiao and Haiwen Zhang.
Plant, Cell & Environment (2024)
One-sentence summary: The OsEIN2-OsEIL1/2 ethylene pathway has negative effect on rice tolerance to low temperature stress through transcriptionally repressing OsICE1-mediated chilling response.
Abstract: "Low temperature severely affects rice development and yield. Ethylene signal is essential for plant development and stress response. Here, we reported that the OsEIN2-OsEIL1/2 pathway reduced OsICE1-dependent chilling tolerance in rice. The overexpressing plants of OsEIN2, OsEIL1 and OsEIL2 exhibited severe stress symptoms with excessive reactive oxygen species (ROS) accumulation under chilling, while the mutants (osein2 and oseil1) and OsEIL2-RNA interference plants (OsEIL2-Ri) showed the enhanced chilling tolerance. We validated that OsEIL1 and OsEIL2 could form a heterodimer and synergistically repressed OsICE1 expression by binding to its promoter. The expression of OsICE1 target genes, ROS scavenging- and photosynthesis-related genes were downregulated by OsEIN2 and OsEIL1/2, which were activated by OsICE1, suggesting that OsEIN2-OsEIL1/2 pathway might mediate ROS accumulation and photosynthetic capacity under chilling by attenuating OsICE1 function. Moreover, the association analysis of the seedling chilling tolerance with the haplotype showed that the lower expression of OsEIL1 and OsEIL2 caused by natural variation might confer chilling tolerance on rice seedlings. Finally, we generated OsEIL2-edited rice with an enhanced chilling tolerance. Taken together, our findings reveal a possible mechanism integrating OsEIN2-OsEIL1/2 pathway with OsICE1-dependent cascade in regulating chilling tolerance, providing a practical strategy for breeding chilling-tolerant rice."
Authors: Golam Jalal Ahammed, Zhe Li, Jingying Chen, Yifan Dong, Kehao Qu, Tianmeng Guo, Fenghua Wang, Airong Liu, Shuangchen Chen and Xin Li.
Plant Physiology and Biochemistry (2024)
Highlights: • Reactive oxygen species (ROS) are crucial signaling molecules in plants. • Melatonin is an antioxidant with ROS scavenging potential and a novel plant hormone. • Environmental stress triggers ROS production and melatonin synthesis in plants. • Melatonin can safeguard plants from a wide range of biotic and abiotic stress. • RBOH-derived apoplastic ROS act downstream of melatonin to mediate stress tolerance.
Abstract: "Reactive oxygen species (ROS) are crucial signaling molecules in plants that play multifarious roles in prompt response to environmental stimuli. Despite the classical thoughts that ROS are toxic when accumulate in excess, recent advances in plant ROS signaling biology reveal that ROS participate in biotic and abiotic stress perception, signal integration, and stress-response network activation, hence contributing to plant defense and stress tolerance. ROS production, scavenging and transport are fine-tuned by plant hormones and stress-response signaling pathways. Crucially, the emerging plant hormone melatonin attenuates excessive ROS accumulation under stress, whereas ROS signaling mediates melatonin-induced plant developmental response and stress tolerance. In particular, RESPIRATORY BURST OXIDASE HOMOLOG (RBOH) proteins responsible for apoplastic ROS generation act downstream of melatonin to mediate stress response. In this review, we discuss promising developments in plant ROS signaling and how ROS might mediate melatonin-induced plant resilience to environmental stress."
Via Golam Jalal Ahammed
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: 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: Pinging Fang, Yannan Hu, Qinwei Guo, Lan Li and Pei Xu.
Plant Stress (2023)
Highlights: • The discovery and signaling transduction of KAR is summarized. • An overview of the recent advances in KAR actions under abiotic stress is provided. • The involvement of redox signals in KAR-regulated stress responses is highlighted.
Abstract: Karrikins (KARs) are bioactive butenolide molecules that were initially discovered as germination stimulants in the smoke generated from burned plant materials. The past decades have witnessed the unraveling of KARs as a group of potential plant hormones that impact various aspects of plant physiology, from regulation of light responses and controlling root morphology, to modulation of secondary metabolism. KARs share a similar structure with strigolactones (SLs), and they activate similar signaling pathways where the interaction of α/β hydrolases with the F-box protein MORE AXILLARY GROWTH 2 (MAX2) is involved. Upon binding with KARs, the α/β hydrolase KAI2 (KARRIKIN INSENSITIVE 2) interacts with MAX2, which in turn activates the downstream signals by promoting the degradation of SMAX1/SMXL2 (SUPPRESSOR OF MAX2 1/SMX1-LIKE). Recent accumulating evidence has proved that KARs act as a protective agent regulating plant adaptation to abiotic stresses, particularly drought, salinity, and extreme temperature; however, these functions have not been widely perceived. This review revisits the knowledge of the characteristics and signals transduction of KARs in plants, with a focus on the interplay of KARs and redox signals in modulating plant tolerance to abiotic stresses. This collection of information is valuable for better understanding plant-environment interactions and will help create stress-tolerant crops and achieve the goal of agricultural and ecological sustainability."
Authors: Miguel-Ángel Torres and Diego José Berlanga.
Molecular Plant (2023)
Excerpt: "In the accompanying article, Wang et al. (2023) identify in rice a new kinase that activates RBOH-dependent ROS production in ABA signaling. Rice Ca2+/CALMODULIN-DEPENDENT PROTEIN KINASE (CCaMK) DOESN'T MAKE INFECTIONS 3 (DMI3) was previously recognized as a positive regulator of ABA signaling, increasing ABA sensitivity and stress tolerance, and promoting the induction of antioxidant defences (Ni et al., 2019). In the present study, Wang et al. (2023) identify OsRBOHB as the main NADPH oxidase involved in ABA induced H2O2 production, and show that OsDMI3 interacts with and phosphorylates OsRBOHB at Ser-191. This phosphorylation positively regulates and enhances the production of H2O2 in ABA signaling, thereby increasing the sensitivity of seed germination and root growth to ABA and the tolerance of rice plants to drought and oxidative stress. The discovery of this novel regulatory mechanism of RBOH-dependent ROS production linked to Ca2+ signaling, added to the recent identification of proteins functioning as H2O2 sensors, point to the existence of positive feed-back regulatory loops to amplify H2O2 signaling and enhance downstream responses (Figure 1)."
Text of Figure: "Several amplification loops enhance H2O2 production and Ca2+ signaling in response to ABA. In the presence of ABA, loss of inhibition by class A PP2Cs activates SnRK2s (like OsSAPK8/9/10) that phosphorylate different targets, including RBOHs (Ser-140 in OsRBOHB) to trigger initial apoplastic H2O2 production. Downstream H2O2 targets comprise receptor kinases (like AtHPCA1) that activate channels allowing Ca+2 entry into the cytosol. Ca+2 will directly stimulate RBOH activity via its EF hands or indirectly through the activation of CCaMK (OsDMI3) that phosphorylates Ser-191 in OsRBOHB and further enhance RBOH activity to produce a second and sustained ABA-induced H2O2 burst. H2O2 can also contribute to enhance RBOH activity by oxidizing cysteins in clue inhibitors of ABA signaling, thus conforming additional amplification loops. H2O2 entering the cell through aquaporins (AQP) can oxidize clade K PP2Cs (OsPP45), releasing the inhibition of OsDMI3. In addition, H2O2 can oxidize thiol peroxidase PRXIIB, which forms a disulfide bridge with and inhibits clade A PP2Cs (AtABI2). Inhibition of these phosphatases allows further activation of SnRK2s to enhance downstream signaling, including phosphorylation of RBOH at Ser-140. These various positive feedback loops will augment H2O2 (and Ca+2) signaling to enhance ABA responses. Crosses indicate loss of inhibition of signaling components by ABA (blue) or H2O2 (red) that amplify signaling."
Authors: Jieting Wu, Sidi Lv, Lei Zhao, Tian Gao, Chang Yu, Jianing Hu and Fang Ma.
Planta (2023)
Main conclusion: This review summarizes the anti-stress effects of flavonoids in plants and highlights its role in the regulation of polar auxin transport and free radical scavenging mechanism.
Abstract: "As secondary metabolites widely present in plants, flavonoids play a vital function in plant growth, but also in resistance to stresses. This review introduces the classification, structure and synthetic pathways of flavonoids. The effects of flavonoids in plant stress resistance were enumerated, and the mechanism of flavonoids in plant stress resistance was discussed in detail. It is clarified that plants under stress accumulate flavonoids by regulating the expression of flavonoid synthase genes. It was also determined that the synthesized flavonoids are transported in plants through three pathways: membrane transport proteins, vesicles, and bound to glutathione S-transferase (GST). At the same time, the paper explores that flavonoids regulate polar auxin transport (PAT) by acting on the auxin export carrier PIN-FORMED (PIN) in the form of ATP-binding cassette subfamily B/P-glycoprotein (ABCB/PGP) transporter, which can help plants to respond in a more dominant form to stress. We have demonstrated that the number and location of hydroxyl groups in the structure of flavonoids can determine their free radical scavenging ability and also elucidated the mechanism by which flavonoids exert free radical removal in cells. We also identified flavonoids as signaling molecules to promote rhizobial nodulation and colonization of arbuscular mycorrhizal fungi (AMF) to enhance plant–microbial symbiosis in defense to stresses. Given all this knowledge, we can foresee that the in-depth study of flavonoids will be an essential way to reveal plant tolerance and enhance plant stress resistance."
Authors: Sarika Singh, Moin Uddin, M. Masroor A. Khan, Aman Sobia Chishti, Sangram Singh and Urooj Hassan Bhat.
Plant Stress (2023)
Highlights: • Smoke and its active ingredients promote seed germination, seedling growth and mitigation of abiotic stresses. • Plant-derived smoke and karrikin maintain oxidative equilibrium by controlling the cell's antioxidant apparatus. • Plant derived smoke and karrikin interacts with phytohormones to reduce the oxidative damage, drought, and heavy metal stress.
Abstract: "Plant-derived smoke has the potential to be used in tissue culture, agriculture, and ecological restoration. Karrikin is an active constituent of plant-derived smoke and a strong germination stimulant. Karrikin and strigolactone share comparable signaling pathways and exhibit structural similarities. Smoke and its active ingredients promote seed germination as well as other physiological activities, such as seedling growth and abiotic stress mitigation. Additionally, plant-derived smoke and karrikin maintain oxidative equilibrium by controlling the cell's antioxidant machinery. In order to reduce abiotic challenges such oxidative damage, drought, and heavy metal stress, plant derived smoke as well as karrikin interacts with a number of phytohormones. Various genomics studies have been progressed in revealing the mechanism of action of plant derived smoke and karrikin in mitigation of abiotic stresses in plants. This review article focuses on the role of plant-derived smoke and karrikinolide in improving stress tolerance."
Authors: Soumya Mukherjee, Francisco J. Corpas.
Plant, Cell & Environment (2023)
Abstract: "Hydrogen peroxide (H2O2) is a reactive oxygen species (ROS) and a key modulator of the development and architecture of the root system under physiological and adverse environmental conditions. Nitric oxide (NO) and hydrogen sulfide (H2S) also exert myriad functions on plant development and signaling. Accumulating pieces of evidence show that depending upon the dose and mode of applications, NO and H2S can have synergistic or antagonistic actions in mediating H2O2 signaling during root development. Thus, H2O2-NO- H2S crosstalk might essentially impart tolerance to elude oxidative stress in roots. Growth and proliferation of root apex involve crucial orchestration of NO- and H2S-mediated ROS signaling which also comprise other components including mitogen-activated protein kinase, cyclins, cyclin-dependent kinases, respiratory burst oxidase homolog (RBOH), and Ca2+ flux. This assessment provides a comprehensive update on the cooperative roles of NO and H2S in modulating H2O2 homeostasis during root development, abiotic stress tolerance, and root-microbe interaction. Furthermore, it also analyses the scopes of some fascinating future investigations associated with strigolactone and karrikins concerning H2O2-NO-H2S crosstalk in plant roots."
Author: Guadalupe L. Fernández-Milmanda.
Plant Physiology (2023)
Excerpts: "In this issue of Plant Physiology, Myers et al. (2023) used a highly sensitive whole-plant live ROS imaging method (Fichman et al., 2019, Figure 1) to uncover the role of several plant hormones in regulating ROS wave production in response to high light (HL) stress or mechanical wounding."
"In Arabidopsis (Arabidopsis thaliana), JA responses generally antagonize those of SA (Caarls et al., 2015), which also accumulates in local and systemic leaves of plants stressed by the local application of HL (Devireddy et al., 2018; Devireddy et al., 2020). In contrast to JA treatment, the direct application of SA enhanced the intensity of the systemic ROS wave produced after HL or wounding."
"In summary, Myers and collaborators took advantage of their whole-plant live ROS imaging system to explore the involvement of several phytohormones in the production of ROS waves in response to HL stress or wounding. They showed that JA and SA control this response in an opposite manner, i.e., SA enhances while JA represses ROS waves, although the mechanism behind this antagonism awaits further research."
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Authors: Puja Ghosh and Aryadeep Roychoudhury.
Journal of Plant Growth Regulation (2024)
Abstract: "Plants are constantly exposed to a wide range of stress situations, such as biotic stressors caused by pathogenic microbes and herbivores, as well as abiotic stress factors like drought, salinity, and severe temperature. Plants have developed an intricate and sophisticated network of molecular signaling in response to various stresses that allow them to recognize and respond to challenging circumstances. Plant peptides have emerged as key participants in orchestrating biotic and abiotic stress responses, as well as taking part in signaling pathways for reactive oxygen species (ROS). ROS play a key role as secondary messengers in stress signaling and include chemicals, including superoxide, hydrogen peroxide, and singlet oxygen. This exhaustive review investigates the multiple functions of plant peptides in ROS signaling and stress responses and clarifies the interaction between plant peptide-mediated stress responses and ROS signaling. We have highlighted several plant peptide classes such as defense peptides, antimicrobial peptides and signaling peptides that contribute to the complex interaction between abiotic and biotic stress response pathways. A thorough overview of the complex regulatory network that permits plants to flourish under demanding environmental conditions is presented by synthesizing recent gains in our knowledge of the functions of plant peptides in stress responses and ROS signaling. We have also highlighted the fact that knowledge of such peptide-mediated signaling may be used for crop improvement that would increase agricultural sustainability and stress tolerance, ultimately boosting food security and environmental resilience on a global scale."
Authors: Muhmmad Asad Ullah Asad, Zhang Yan, Lujian Zhou, Xianyue Guan and Fangmin Cheng.
Plant Physiology and Biochemistry (2024)
Highlights: • Sugars play an essential role in the regulations of leaf senescence. • Abiotic stresses trigger sugar signaling by inducing reactive oxygen species burst. • Sugar signaling interact with plant hormones and protein kinase to regulates leaf senescence. • Abiotic stresses target sugar signaling to regulate photosynthesis inhibition and programmed cell death (PCD).
Abstract: "Plants have evolved the adaptive capacity to mitigate the negative effect of external adversities at chemical, molecular, cellular, and physiological levels. This capacity is conferred by triggering the coordinated action of internal regulatory factors, in which sugars play an essential role in the regulating chloroplast degradation and leaf senescence under various stresses. In this review, we summarize the recent findings on the senescent-associated changes in carbohydrate metabolism and its relation to chlorophyll degradation, oxidative damage, photosynthesis inhibition, programmed cell death (PCD), and sink-source relation as affected by abiotic stresses. The action of sugar signaling in regulating the initiation and progression of leaf senescence under abiotic stresses involves interactions with various plant hormones, reactive oxygen species (ROS) burst, and protein kinases. This discussion aims to elucidate the complex regulatory network and molecular mechanisms that underline sugar-induced leaf senescence in response to various abiotic stresses. The imperative role of sugar signaling in regulating plant stress responses potentially enables the production of crop plants with modified sugar metabolism. This, in turn, may facilitate the engineering of plants with improved stress responses, optimal life span and higher yield achievement."
Authors: Ronald J. Myers, María Ángeles Peláez-Vico and Yosef Fichman.
Plant, Cell & Environment (2024)
One-sentence summary: Reactive oxygen species waves can be triggered by varying types of stress stimuli in local tissues and spread from cell to cell to induce systemic acclimation.
Abstract: "Reactive oxygen species (ROS) play a critical role in plant development and stress responses, acting as key components in rapid signalling pathways. The ‘ROS wave’ triggers essential acclimation processes, ultimately ensuring plant survival under diverse challenges. This review explores recent advances in understanding the composition and functionality of the ROS wave within plant cells. During their initiation and propagation, ROS waves interact with other rapid signalling pathways, hormones and various molecular compounds. Recent research sheds light on the intriguing lack of a rigid hierarchy governing these interactions, highlighting a complex interplay between diverse signals. Notably, ROS waves culminate in systemic acclimation, a crucial outcome for enhanced stress tolerance. This review emphasizes the versatility of ROS, which act as flexible players within a network of short- and long-term factors contributing to plant stress resilience. Unveiling the intricacies of these interactions between ROS and various signalling molecules holds immense potential for developing strategies to augment plant stress tolerance, contributing to improved agricultural practices and overall ecosystem well-being."
Authors: Sufian Ikram, Yang Li, Chai Lin, Debao Yi, Wang Heng, Qiang Li, Lu Tao, Yu Hongjun and Jiang Weijie.
Journal of Plant Physiology (2024)
Abstract: "Selenium (Se) is an essential micronutrient for both human and animals. Plants serve as the primary source of Se in the food chain. Se concentration and availability in plants is influenced by soil properties and environmental conditions. Optimal Se levels promote plant growth and enhance stress tolerance, while excessive Se concentration can result in toxicity. Se enhances plants ROS scavenging ability by promoting antioxidant compound synthesis. The ability of Se to maintain redox balance depends upon ROS compounds, stress conditions and Se application rate. Furthermore, Se-dependent antioxidant compound synthesis is critically reliant on plant macro and micro nutritional status. As these nutrients are fundamental for different co-factors and amino acid synthesis. Additionally, phytohormones also interact with Se to promote plant growth. Hence, utilization of phytohormones and modified crop nutrition can improve Se-dependent crop growth and plant stress tolerance. This review aims to explore the assimilation of Se into plant proteins, its intricate effect on plant redox status, and the specific interactions between Se and phytohormones. Furthermore, we highlight the proposed physiological and genetic mechanisms underlying Se-mediated phytohormone-dependent plant growth modulation and identified research opportunities that could contribute to sustainable agricultural production in the future."
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: 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: Muhammad Saad Shoaib Khan, Sulaiman Ahmed, Aziz ul Ikram, Fakhir Hannan, Muhammad Umair Yasin, Jin Wang, Biying Zhao, Faisal Islam and Jian Chen.
Physiologia Plantarum (2023)
Highlights: • Melatonin acts as a redox network regulator in plants via regulating secondary messengers signaling. • Melatonin regulates the activity of redox-sensitive proteins and transcription factors. • Melatonin influences gene expression and physiological processes in response to stresses. • Melatonin synergically work with other hormones to confer plant resistance and stress adaptability.
Abstract: "Plants being sessile in nature, are exposed to unwarranted threats as a result of constantly changing environmental conditions. These adverse factors can have negative impacts on their growth, development, and yield. Hormones are key signaling molecules enabling cells to respond rapidly to different external and internal stimuli. In plants, melatonin (MT) plays a critical role in the integration of various environmental signals and activation of stress-response networks to develop defense mechanisms and plant resilience. Additionally, melatonin can tackle the stress-induced alteration of cellular redox equilibrium by regulating the expression of redox homeostasis-related genes and proteins. The purpose of this article is to compile and summarize the scientific research pertaining to MT's effects on plants' resilience to biotic and abiotic stresses. Here, we have summarized that MT exerts a synergistic effect with other phytohormones, for instance, ethylene, jasmonic acid, and salicylic acid, and activates plant defense-related genes against phytopathogens. Furthermore, MT interacts with secondary messengers like Ca2+, nitric oxide, and reactive oxygen species to regulate the redox network. This interaction triggers different transcription factors to alleviate stress-related responses in plants. Hence, the critical synergic role of MT with diverse plant hormones and secondary messengers demonstrates phytomelatonin's importance in influencing multiple mechanisms to contribute to plant resilience against harsh environmental factors."
Authors: Verena Iven, Isabeau Vanbuel, Sophie Hendrix and Ann Cuypers.
Journal of Experimental Botany (2023)
Abstract: "Cadmium (Cd) uptake from polluted soils inhibits plant growth and disturbs physiological processes, at least partly due to disturbances in the cellular redox environment. Although the sulfur-containing antioxidant glutathione is important in maintaining redox homeostasis, its role as an antioxidant can be overruled by its involvement in Cd chelation as a phytochelatin precursor. Following Cd exposure, plants rapidly invest in phytochelatin production, thereby disturbing the redox environment by transiently depleting glutathione concentrations. Consequently, a network of signalling responses is initiated, in which the phytohormone ethylene is an important player involved in the recovery of glutathione levels. Furthermore, these responses are intricately connected to organellar stress signalling and autophagy, and contribute to cell fate determination. In general, this may pave the way for acclimation (e.g. restoration of glutathione levels and organellar homeostasis) and plant tolerance in the case of mild stress conditions. This review addresses connections between these players and discusses the possible involvement of the gasotransmitter hydrogen sulfide in plant acclimation to Cd exposure.
Authors: Qingwen Wang, Tao Shen, Lan Ni, Chao Chen, Jingjing Jiang, Zhenzhen Cui, Shuang Wang, Fengjuan Xu, Runjiao Yan and Mingyi Jiang.
Molecular Plant (2023)
Abstract: "In rice, the Ca2+/calmodulin-dependent protein kinase OsDMI3 is an important positive regulator of abscisic acid (ABA) signaling. In ABA signaling, H2O2 is required for ABA-induced activation of OsDMI3, which in turn increase H2O2 production. However, how OsDMI3 regulates H2O2 production in ABA signaling remains unknown. Here we show that OsRbohB is the main NADPH oxidase involved in ABA-induced H2O2 production and ABA-mediated physiological responses. OsDMI3 directly interacts with and phosphorylates OsRbohB at Ser-191, which is OsDMI3-mediated site-specific phosphorylation in ABA signaling. Further analyses revealed that OsDMI3-mediated OsRbohB Ser-191 phosphorylation positively regulates the activity of NADPH oxidase and the production of H2O2 in ABA signaling, thereby enhancing the sensitivity of seed germination and root growth to ABA and plant tolerance to water stress and oxidative stress. Moreover, we discovered that the OsDMI3-mediated OsRbohB phosphorylation and H2O2 production is dependent on the sucrose non-fermenting 1-related protein kinases SAPK8/9/10, which phosphorylate OsRbohB at Ser-140 in ABA signaling. Taken together, these results not only reveal an important regulatory mechanism that directly activates Rboh for ABA-induced H2O2 production but also uncover the importance of this regulatory mechanism in ABA signaling."
Authors: Lei Xu, Hongyu Zhao, Junbin Wang, Xuming Wang, Xianqing Jia, Long Wang, Zhuang Xu, Ruili Li, Kun Jiang, Zhixiang Chen, Jie Luo, Xiaodong Xie and Keke Yi.
New Phytologist (2023)
Abstract: "● The basal levels of salicylic acid (SA) vary dramatically among plant species. In the shoot, for example, rice contains almost 100 times higher SA levels than Arabidopsis. Despite its high basal levels, neither the biosynthetic pathway nor the biological functions of SA are well understood in rice. ● Combining with metabolites analysis, physiological, and genetic approaches, we found that the synthesis of basal SA in rice shoot is dependent on OsAIM1, which encodes a beta-oxidation enzyme in the phenylalanine ammonia-lyase (PAL) pathway. ● Compromised SA accumulation in the Osaim1 mutant led to a lower shoot temperature than wild-type plants. However, this shoot temperature defect resulted from increased transpiration due to elevated steady-state stomatal aperture in the mutant. Furthermore, the high basal SA level is required for sustained expression of OsWRKY45 to modulate the steady-state stomatal aperture and shoot temperature in rice. ● Taken together, these results provide the direct genetic evidence for the critical role of the PAL pathway in the biosynthesis of high basal level SA in rice, which plays an important role in the regulation of steady-state stomatal aperture to promote fitness under stress conditions."
Authors: Carolina A. Torres and Carlos R. Figueroa.
In book: "Plant Hormones and Climate Change" (2023)
Abstract: "Climate change and global warming are causing extreme and unpredictable weather during the growing season. Heat waves are more frequent and extreme in many parts of the globe, causing heat stress (HS) on top of other abiotic stress such as photooxidative stress (POS) in plant tissues including the growing fruit. Defense mechanisms and acclimation are key for these tissues to survive, for which plant hormones play a pivotal role in engaging biochemical mechanisms to accomplish this. Consequently, fruit can either grow and mature normally or develop sun-related disorders such as sunscald or sunburn. Either way, sun-exposed fruit tissue has a unique phenotype involving metabolites, physiological traits, and textural characteristics. This chapter reviews some of the biochemical events in fruit under those environmental conditions, focused on the role of phytohormones as key elements in signal transduction and gene expression in response to oxidative stress derived from exposition to high light (HL) combined with heat stress (HS), which finally implies the modulation of defense mechanisms. In addition, we discuss the role of exogenous plant growth regulators as a tool to manage adverse abiotic stresses under the current and future climate change scenario."
Authors: Shenghui Li, Sha Liu, Qiong Zhang, Meixiang Cui, Min Zhao, Nanyang Li, Suna Wang, Ruigang Wu, Lin Zhang, Yunpeng Cao and Lihu Wang.
Frontiers in Plant science (2022)
Abstract: "The plant hormone ABA (abscisic acid) plays an extremely important role in plant growth and adaptive stress, including but are not limited to seed germination, stomatal closure, pathogen infection, drought and cold stresses. Reactive oxygen species (ROS) are response molecules widely produced by plant cells under biotic and abiotic stress conditions. The production of apoplast ROS is induced and regulated by ABA, and participates in the ABA signaling pathway and its regulated plant immune system. In this review, we summarize ABA and ROS in apoplast ROS production, plant response to biotic and abiotic stresses, plant growth regulation, ABA signal transduction, and the regulatory relationship between ABA and other plant hormones. In addition, we also discuss the effects of protein post-translational modifications on ABA and ROS related factors."
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