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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: Tianshun Zhou, Dong Yu, Liubing Wu, Yusheng Xu, Meijuan Duan and Dingyang Yuan.
Rice Science (2024)
Abstract: "Long-term storage of crop seeds is critical for germplasm resource conservation, food supply and sustainable production. As a major food, rice has a huge stock for production and consumption worldwide, while easily losing food value and seed viability during storage. Thus, understanding the physiological responses and molecular mechanisms of aging tolerance lays the foundation for improving seed storability in rice. This review illustrates the current advances in influential factors, evaluation methods, and identification indexes of seed storability. It also discusses the physiological consequences, molecular mechanisms, and methods to breed aging-tolerant rice in detail. Finally, it points out some challenges in the research of seed storability that need to be addressed in the future. This review provides a theoretical basis and research direction for revealing the mechanisms underlying seed storability and breeding aging tolerant rice."
Authors: Hanqian Feng, Jinjuan Tan and Zhiping Deng.
Journal of Experimental Botany (2023)
Abstract: "Ubiquitination, a vital post-translational modification in plants, plays a significant role in regulating protein activity, localization, and stability. This process occurs through a complex enzyme cascade that involves E1, E2, and E3 enzymes, leading to the covalent attachment of ubiquitin molecules to substrate proteins. Conversely, deubiquitinating enzymes (DUBs) work in opposition to this process by removing ubiquitin moieties. Despite extensive research on ubiquitination in plants, our understanding of the function of DUBs is still emerging. UBP12 and UBP13, two plant DUBs, have received much attention recently and are shown to play pivotal roles in hormone signaling, light perception, photoperiod responses, leaf development, senescence, and epigenetic transcriptional regulation. This review summarizes current knowledge about these two enzymes, highlighting the central role of deubiquitination in regulating the abundance and activity of critical regulators like receptor kinases and transcriptional factors during phytohormone and developmental signaling."
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."
Authors: Jenna Lihavainen, Jan Šimura, Pushan Bag, Nazeer Fataftah, Kathryn Megan Robinson, Nicolas Delhomme, Ondřej Novák, Karin Ljung and Stefan Jansson.
Nature Communications (2023)
Editor's view: Deciduous trees exhibit autumn senescence driven by environmental seasonality. Here, the authors show that senescence timing in aspen tree genotypes depends on environmental changes but also on the ability of each genotype to sustain stress tolerance mediated by the phytohormone salicylic acid.
Abstract: "Deciduous trees exhibit a spectacular phenomenon of autumn senescence driven by the seasonality of their growth environment, yet there is no consensus which external or internal cues trigger it. Senescence starts at different times in European aspen (Populus tremula L.) genotypes grown in same location. By integrating omics studies, we demonstrate that aspen genotypes utilize similar transcriptional cascades and metabolic cues to initiate senescence, but at different times during autumn. The timing of autumn senescence initiation appeared to be controlled by two consecutive “switches”; 1) first the environmental variation induced the rewiring of the transcriptional network, stress signalling pathways and metabolic perturbations and 2) the start of senescence process was defined by the ability of the genotype to activate and sustain stress tolerance mechanisms mediated by salicylic acid. We propose that salicylic acid represses the onset of leaf senescence in stressful natural conditions, rather than promoting it as often observed in annual plants."
Authors: Aishwarye Sharma, Harsha Samtani, Karishma Sahu, Arun Kumar Sharma, Jitendra Paul Khurana and Paramjit Khurana.
International Journal of Biological Macromolecules (2023)
Abstract: "Transcription factors play important roles in governing plant responses upon changes in their ambient conditions. Any fluctuation in the supply of critical requirements for plants, such as optimum light, temperature, and water leads to the reprogramming of gene-signaling pathways. At the same time, plants also evaluate and shift their metabolism according to the various stages of development. Phytochrome-Interacting Factors are one of the most important classes of transcription factors that regulate both developmental and external stimuli-based growth of plants. This review focuses on the identification of PIFs in various organisms, regulation of PIFs by various proteins, functions of PIFs of Arabidopsis in diverse developmental pathways such as seed germination, photomorphogenesis, flowering, senescence, seed and fruit development, and external stimuli-induced plant responses such as shade avoidance response, thermomorphogenesis, and various abiotic stress responses. Recent advances related to the functional characterization of PIFs of crops such as rice, maize, and tomato have also been incorporated in this review, to ascertain the potential of PIFs as key regulators to enhance the agronomic traits of these crops. Thus, an attempt has been made to provide a holistic view of the function of PIFs in various processes in plants.
Authors: Omar A. Hewedy, Nabil I. Elsheery, Ali M. Karkour, Neveen Elhamouly, Ramadan A. Arafa, Ghada Abd-Elmonsef Mahmoud, Mona F.-A. Dawood, Walaa E. Hussein, Abdelaziz Mansour, Dina H. Amin, Suleyman I. Allakhverdiev, Marek Zivcak, Marian Brestic.
Environmental and Experimental Botany (2023)
Highlights • Jasmonic acid (JA) plays crucial roles in crop development, organ formation and functions • There is a high diversity of phytohormone signaling pathways and genes associated with jasmonates • JA crosstalk with other plant hormones and regulates numerous enzymes and proteins associated with plant resistance • An integrated view of JA biosynthesis at the molecular levels, gene expression regulation, and functional role of JA in helping plant species respond to stressful conditions is presented
Abstract: "Jasmonic acid (JA) or methyl jasmonate (MeJA) are master regulators of plant development and stress response against pathogens and environmental fluctuations. Thus, JA is an important stress-associated phytohormone that can promote various defense interactions, regulate stomatal openness, synthesis of antimicrobial substances, or plant cell reprogramming. Numerous studies also demonstrated that plants thriving under environmental fluctuations stresses are linked to the JA response, revealing that JA application can alleviate the damage of abiotic stress by improving plant tolerance. Therefore, jasmonic acid and amino acid conjugate (JA-Ile) represent stress hormones that improve crop resilience under environmental fluctuations. In addition, JA modulates the plant growth and developmental stages by regulating the crosstalk between JA and the main plant hormone groups, balancing plant development and defense mechanism against pathogen attacks. The effects on various processes and plant structures, such as seed germination, primary root/root hair growth, fruit development, pollen maturation, senescence, and regeneration, have been documented for jasmonates. Therefore, we reviewed the functional influence of jasmonates, involving sensing and regulating their signaling under harsh conditions, which is becoming a top priority for agriculture. In addition, the crosstalks with other phytohormones, such as auxin, salicylic acid, ethylene, and the plant-pathogen interactions, are discussed."
Authors: Peixin Huang, Zhonghai Li and Hongwei Guo.
Frontiers in Plant Science (2022)
Abstract: "Leaf senescence is the last stage of leaf development, manifested by leaf yellowing due to the loss of chlorophyll, along with the degradation of macromolecules and facilitates nutrient translocation from the sink to the source tissues, which is essential for the plants' fitness. Leaf senescence is controlled by a sophisticated genetic network that has been revealed through the study of the molecular mechanisms of hundreds of senescence-associated genes (SAGs), which are involved in multiple layers of regulation. Leaf senescence is primarily regulated by plant age, but also influenced by a variety of factors, including phytohormones and environmental stimuli. Phytohormones, as important signaling molecules in plant, contribute to the onset and progression of leaf senescence. Recently, peptide hormones have been reported to be involved in the regulation of leaf senescence, enriching the significance of signaling molecules in controlling leaf senescence. This review summarizes recent advances in the regulation of leaf senescence by classical and peptide hormones, aiming to better understand the coordinated network of different pathways during leaf senescence."
Authors: Jenna Lihavainen, Jan Šimura, Pushan Bag, Nazeer Fataftah, Kathryn Megan Robinson, Nicolas Delhomme, Ondřej Novák, Karin Ljung and Stefan Jansson.
bioRxiv (2022)
Abstract: "European aspen (Populus tremula L.) undergoes a coordinated senescence program during autumn; however, it is not known what exactly triggers it. To identify the cellular program leading to senescence, we utilized natural variation among Swedish aspen genotypes in a common garden to study senescence timing and the underlying changes in leaf phytohormone and transcriptome profiles. Apart from the patterns of major transcriptional cascade that was similar between the genotypes and closely associated with cytokinin and auxin metabolite levels and gradually decreasing air temperature during autumn, we detected patterns that consistently preceded or coincided with senescence onset in individual genotypes. Another cascade seemed to respond to short-term changes in weather conditions that re-wired the transcriptional network; the up-regulation of genes related to ethylene and abiotic stress, programmed cell death and translation occurred first in the early-senescing genotypes and later in the late one. Network analyses displayed a connection between the two cascades, metabolic stress and immunity responses mediated by salicylic acid (SA)-signalling pathway that was repressed along with SA levels at senescence onset. We propose that autumn senescence in aspen trees is affected by environmental variation that evokes stress and the timing is fine-tuned by their stress tolerance mechanism."
Authors: Aakansha Kanojia, Deny K. Shrestha and Paul P. Dijkwel.
Cellular and Molecular Life Sciences (2021)
Abstract: "Ageing in plants is a highly coordinated and complex process that starts with the birth of the plant or plant organ and ends with its death. A vivid manifestation of the final stage of leaf ageing is exemplified by the autumn colours of deciduous trees. Over the past decades, technological advances have allowed plant ageing to be studied on a systems biology level, by means of multi-omics approaches. Here, we review some of these studies and argue that these provide strong support for basic metabolic processes as drivers for ageing. In particular, core cellular processes that control the metabolism of chlorophyll, amino acids, sugars, DNA and reactive oxygen species correlate with leaf ageing. However, while multi-omics studies excel at identifying correlative processes and pathways, molecular genetic approaches can provide proof that such processes and pathways control ageing, by means of knock-out and ectopic expression of predicted regulatory genes. Therefore, we also review historic and current molecular evidence to directly test the hypotheses unveiled by the systems biology approaches. We found that the molecular genetic approaches, by and large, confirm the multi-omics-derived hypotheses with notable exceptions, where there is scant evidence that chlorophyll and DNA metabolism are important drivers of leaf ageing. We present a model that summarises the core cellular processes that drive leaf ageing and propose that developmental processes are tightly linked to primary metabolism to inevitably lead to ageing and death."
Authors: Yongfeng Guo, Guodong Ren, Kewei Zhang, Zhonghai Li, Ying Miao and Hongwei Guo.
Molecular Horticulture (2021)
Abstract: "Leaf senescence, the last stage of leaf development, is a type of postmitotic senescence and is characterized by the functional transition from nutrient assimilation to nutrient remobilization which is essential for plants’ fitness. The initiation and progression of leaf senescence are regulated by a variety of internal and external factors such as age, phytohormones, and environmental stresses. Significant breakthroughs in dissecting the molecular mechanisms underpinning leaf senescence have benefited from the identification of senescence-altered mutants through forward genetic screening and functional assessment of hundreds of senescence-associated genes (SAGs) via reverse genetic research in model plant Arabidopsis thaliana as well as in crop plants. Leaf senescence involves highly complex genetic programs that are tightly tuned by multiple layers of regulation, including chromatin and transcription regulation, post-transcriptional, translational and post-translational regulation. Due to the significant impact of leaf senescence on photosynthesis, nutrient remobilization, stress responses, and productivity, much effort has been made in devising strategies based on known senescence regulatory mechanisms to manipulate the initiation and progression of leaf senescence, aiming for higher yield, better quality, or improved horticultural performance in crop plants. This review aims to provide an overview of leaf senescence and discuss recent advances in multi-dimensional regulation of leaf senescence from genetic and molecular network perspectives. We also put forward the key issues that need to be addressed, including the nature of leaf age, functional stay-green trait, coordination between different regulatory pathways, source-sink relationship and nutrient remobilization, as well as translational researches on leaf senescence."
Authors: Marina Pérez-Llorca and Sergi Munné-Bosch.
GeroScience (2021)
Review: "Aging, stress, and senescence in plants are interconnected processes that determine longevity. We focus here on compiling and discussing our current knowledge on the mechanisms of development that long-lived perennial plants have evolved to prevent and delay senescence. Clonal and nonclonal perennial herbs of various life forms and longevities will be particularly considered to illustrate what biological diversity can teach us about aging as a universal phenomenon. Source–sink relations and redox signaling will also be discussed as examples of regulatory mechanisms of senescence at the organ level. Whether or not effective mechanisms that biological diversity has evolved to completely prevent the wear and tear of aging will be applicable to human aging in the near future ultimately depends on ethical aspects."
Authors: Yu-Qing Zhao, Zhong-Wei Zhang, Yang-Er Chen, Chun-Bang Ding, Shu Yuan, Russel J. Reiter and Ming Yuan
Critical Reviews in Plant Sciences (2021)
Abstract: "Delaying early leaf senescence is important for improving photosynthetic efficiency and crop productivity. Melatonin, a multitasking bio-stimulator, participates widely in plant development and stress responses. In recent years, the cumulative researches show that melatonin has the ability to delay senescence in plants. This review covers the most recent advances on the mechanisms of melatonin-mediated leaf senescence. Melatonin biosynthesis in senescing leaves employs an alternative pathway and is significantly regulated by light. Melatonin increases the thickness of leaf cuticle, wax accumulation and the ratio of palisade/spongy of senescing leaves to maintain intact leaf structure. Melatonin eliminates free radicals through a scavenging cascade reaction and induces antioxidants and antioxidant enzymes; and provides better protection against lipid peroxidation via arranging parallel to the bilayers at high concentration. Meanwhile, melatonin’s ability to ensure high photosynthetic efficiency is predominantly attributed to the reduction of chlorophylls and chloroplast proteins degradation, and the acceleration of chlorophyll de novo synthesis. The dual role of melatonin-regulated autophagy is beneficial for maintaining cellular homeostasis. NACs, WRKYs and DREBs play essential roles in melatonin-controlled transcriptional reprogramming of senescing leaves. Additionally, melatonin improves the activity of cytokinin and auxin; and inhibits the action of abscisic acid, ethylene and jasmonic acid to impact indirectly leaf senescence. Epigenetic modification may be part of mechanisms of melatonin-mediated alterations in gene expression. Moreover, selection of germplasms rich in melatonin and application of genetic modification in agriculture are extensively discussed. Further studies are needed to detail the mechanisms of melatonin-mediated signaling transduction in leaf senescence."
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Authors: Kangning Zhang, Hongli Xie, Jiangqi Wen, Jing Zhang, Zeng-Yu Wang, Bin Xu and Maofeng Chai.
Grass Research (2024)
Abstract: "Leaf senescence is a complex biological process regulated by development, phytohormones, and various environmental factors. For forage and turf grasses, controlling leaf senescence can greatly improve forage quality, the amenity of lawn and turf, and the grasses’ stress tolerances. Leaf senescence involves a multitude of gene regulation and metabolic changes, including the alteration of chlorophyll metabolism. Here, we summarized the recent progress of studies on leaf senescence in major forage and turf grass species, such as Medicago truncatula, M. sativa, Lolium perenne, Panicum virgatum, and Agrostis stolonifera, to provide an insight into the development of effective methods for delaying leaf senescence in grass species."
Authors: Foziya Altaf, Shazia Parveen, Sumira Farooq, Mohammad Lateef Lone, Aehsan Ul Haq and Inayatullah Tahir
Theoretical and Experimental Plant Physiology (2024)
Abstract: "Due to the already strained and severely challenged agricultural ecosystems of the modern world, predicted changes in life cycle of plants, including leaf senescence are receiving significant attention from stakeholders. The onset, progression and terminal phases of leaf senescence are greatly influenced by plant hormones. The senescence of leaves is accelerated by ethylene, jasmonic acid (JA), salicylic acid (SA), abscisic acid (ABA), brassinosteroids and strigolactones (SLs), whereas it is postponed by cytokinins (CKs), gibberellic acid (GA) and auxins. The crosstalk and signal transduction pathways between these growth regulators have been found to regulate leaf senescence by orchestrating various developmental and environmental factors. Premature leaf senescence lessens the plant’s nutritional capacity and shortens the vegetative production schedule, prompting an early transition from the vegetative to the reproductive stage and diminishing crop potential. As a result, a complete understanding of leaf senescence and finding novel ways to delay it is crucial for agricultural productivity. The ability to manipulate leaf senescence for agricultural enhancement has been made possible by significant advances in physiological and molecular awareness of leaf senescence. Although studies pertaining to leaf senescence have been given steadily more attention, there are still numerous challenges that need to be resolved. In this perspective, this review focuses on current advances in understanding the leaf senescence by molecular and genetic analyses with an emphasis on hormonal regulation of leaf senescence. We also hypothesize future research to better comprehend leaf senescence by employing various current technologies."
Authors: Muhammad Asad Ullah Asad, Xianyue Guan, Lujian Zhou, Zhao Qian, Zhang Yan and Fangmin Cheng.
Plant Science (2023)
Highlights • Metabolic network and regulatory mechanism underlying nitrogen deficiency-induced leaf senescence are comprehensively discussed. • Sugar acts as a key regulator for leaf senescence and root C/N ratio by connecting with hormone signaling and N metabolism. • Nitrogen deficiency-induced leaf senescence was closely associated with BRs-mediated autophagy and circadian clock response.
Abstract: "Nitrogen (N) is a basic building block that plays an essential role in the maintenance of normal plant growth and its metabolic functions through complex regulatory networks. Such the N metabolic network comprises a series of transcription factors (TFs), with the coordinated actions of phytohormone and sugar signaling to sustain cell homeostasis. The fluctuating N concentration in plant tissues alters the sensitivity of several signaling pathways to stressful environments and regulates the senescent-associated changes in cellular structure and metabolic process. Here, we review recent advances in the interaction between N assimilation and carbon metabolism in response to N deficiency and its regulation to the nutrient remobilization from source to sink during leaf senescence. The regulatory networks of N and sugar signaling for N deficiency-induced leaf senescence is further discussed to explain the effects of N deficiency on chloroplast disassembly, reactive oxygen species (ROS) burst, asparagine metabolism, sugar transport, autophagy process, Ca2+ signaling, circadian clock response, brassinazole-resistant 1 (BZRI), and other stress cell signaling. A comprehensive understanding for the metabolic mechanism and regulatory network underlying N deficiency-induced leaf senescence may provide a theoretical guide to optimize the source-sink relationship during grain filling for the achievement of high yield by a selection of crop cultivars with the properly prolonged lifespan of functional leaves and/or by appropriate agronomic managements."
Authors: Woei-Jiun Guo, Benjamin Pommerrenig, H. Ekkehard Neuhaus and Isabel Keller.
Journal of Plant Physiology (2023)
Abstract: "Endogenous programs and constant interaction with the environment regulate the development of the plant organism and its individual organs. Sugars are necessary building blocks for plant and organ growth and at the same time act as critical integrators of the metabolic state into the developmental program. There is a growing recognition that the specific type of sugar and its subcellular or tissue distribution is sensed and translated to developmental responses. Therefore, the transport of sugars across membranes is a key process in adapting plant organ properties and overall development to the nutritional state of the plant. In this review, we discuss how plants exploit various sugar transporters to signal growth responses, for example, to control the development of sink organs such as roots or fruits. We highlight which sugar transporters are involved in root and shoot growth and branching, how intracellular sugar allocation can regulate senescence, and, for example, control fruit development. We link the important transport processes to downstream signaling cascades and elucidate the factors responsible for the integration of sugar signaling and plant hormone responses.
Author: Hilary J. Rogers.
Biochemical Society Transactions (2023)
Abstract: "Floral senescence is of fundamental interest in understanding plant developmental regulation, it is of ecological and agricultural interest in relation to seed production, and is of key importance to the production of cut flowers. The biochemical changes occurring are well-studied and involve macromolecular breakdown and remobilisation of nutrients to developing seeds or other young organs in the plant. However, the initiation and regulation of the process and inter-organ communication remain to be fully elucidated. Although ethylene emission, which becomes autocatalytic, is a key regulator in some species, in other species it appears not to be as important. Other plant growth regulators such as cytokinins, however, seem to be important in floral senescence across both ethylene sensitive and insensitive species. Other plant growth regulators are also likely involved. Omics approaches have provided a wealth of data especially in ornamental species where genome data is lacking. Two families of transcription factors: NAC and WRKY emerge as major regulators, and omics information has been critical in understanding their functions. Future progress would greatly benefit from a single model species for understanding floral senescence; however, this is challenging due to the diversity of regulatory mechanisms. Combining omics data sets can be powerful in understanding different layers of regulation, but in vitro biochemical and or genetic analysis through transgenics or mutants is still needed to fully verify mechanisms and interactions between regulators."
Author: Ziqiang Zhu.
Journal of Experimental Botany (2023)
Abstract: "Jasmonate is a well-known defence hormone for plants, but it is also necessary for growth and development. Indeed, the identification of the COI1 receptor was based on the jasmonate-triggered response of root growth inhibition. In this special issue, a collection of review papers and two research papers discuss the current state of progress in this field, covering areas from seed germination and flowering to the Jasminum sambac genome."
Authors: Sirisha Kaniganti, Joorie Bhattacharya, Petla Bhanu Prakash and Palakolanu Sudhakar Reddy.
Environmental and Experimental Botany (2022)
Highlights: • SL plays a crucial role in host-parasite interaction. • SL functions in root and shoot architecture regulation, nutrition uptake. • Involved in physiological responses of the plant with phytohormones. • Regulate developmental processes like root hair elongation, leaf senescence. • Play a vital role in biotic and abiotic stress tolerance.
Abstract: "Strigolactones (SLs), initially reported as germination stimulants for Striga lutea were later described for their role in Phelipanche and Orobanche species. SLs were reported in major cereals such as sorghum and maize, which established their importance in host-parasite interaction. Over the past decade, several roles of SLs have been elucidated in root and shoot architecture, pathogen interaction, plant defense mechanism, and nutrition uptake. Additionally, SL plays a key role in abiotic and biotic stress tolerance associated with other phytohormones. The review provides a comprehensive overview of various aspects of SLs and their complex interaction networks with other phytohormones, including ethylene, that exist in the plant system. The review also highlights pivotal points for establishing SLs in commercial agriculture to fully explore their potential in crop improvement and shaping modern agriculture."
Authors: Fengbo Yang, Yuchen Miao, Yuyue Liu, Jose R. Botella, Weiqiang Li, Kun Li and Chun-Peng Song.
Frontiers in Plant Science (2022)
Abstract: "Leaf senescence is an evolutionarily acquired process and it is critical for plant fitness. During senescence, macromolecules and nutrients are disassembled and relocated to actively growing organs. Plant leaf senescence process can be triggered by developmental cues and environmental factors, proper regulation of this process is essential to improve crop yield. Protein kinases are enzymes that modify their substrates activities by changing the conformation, stability, and localization of those proteins, to play a crucial role in the leaf senescence process. Impressive progress has been made in understanding the role of different protein kinases in leaf senescence recently. This review focuses on the recent progresses in plant leaf senescence-related kinases. We summarize the current understanding of the function of kinases on senescence signal perception and transduction, to help us better understand how the orderly senescence degeneration process is regulated by kinases, and how the kinase functions in the intricate integration of environmental signals and leaf age information."
Authors: Riyaz Ahmad Dar, Shaziya Nisar and Inayatullah Tahir.
Scientia Horticulturae (2021)
Highlight: • The present review highlights the current understanding of flower senescence in ethylene sensitive species. • The review gives an updated information and provide the range of genes putatively involved in the implicated pathways leading to flower aging that may be blocked or induced to modify the progression of senescence. • The review also highlights implications of sugars in modulating the effects of ethylene on flower senescence. • The review presents a detailed perspective for future studies to unravel the basic underlying mechanism of flower senescence in general and senescence of ethylene sensitive flowers in particular.
Abstract: "Ethylene plays an important role in the regulation of senescence in ethylene sensitive flowers with little or no role in case of ethylene insensitive flowers. Different growth regulators like gibberellic acid, cytokinins, abscisic acid and polyamines play vital role in regulating important developmental processes of plants through the inhibition of ethylene biosynthesis or perception. These interactions trigger a signaling cascade that regulates several developmental processes including petal wilting/senescence. Recent flower senescence studies have shown that the function of ethylene and its crosstalk with other growth regulators and sugars directly regulates flower senescence by influencing the genes involved in the ethylene-sensitive flower senescence. Additionally, the ethylene response genes involved in the ethylene sensitive flower senescence have been deciphered from a number of plant species. The regulation and characterization of these genes (such as ACC oxidase and ACC synthase) could open new vistas for research in understanding the mechanism of flower senescence. The review presents an in-depth perspective to unravel the basic underlying mechanism of flower senescence in general and senescence of ethylene sensitive flowers in particular."
Authors: Zheng Chen, Wei Jia, Songwei Li, Jiayang Xu and Zicheng Xu.
Frontiers in Plant Science (2021)
Abstract: "Melatonin (MEL) is a pleiotropic agent with crucial functions reported in a variety of stress responses and developmental processes. Although MEL involvement in plant defense against natural leaf senescence has been widely reported, the precise regulatory mechanisms by which it delays stress-induced senescence remain unclear. In this study, we found that foliar spraying of melatonin markedly ameliorated dehydration-induced leaf senescence in Nicotiana tabacum, accompanied by attenuated oxidative damage, expression of senescence-related genes, and reduced endogenous ABA production. Metabolite profiling indicated that melatonin-treated plants accumulated higher concentrations of sugars, sugar alcohol, and organic acids, but fewer concentrations of amino acids in the leaves, than untreated plants after exposure to dehydration. Gene expression analysis revealed that the delayed senescence of stressed plants achieved by melatonin treatment might be partially ascribed to the upregulated expression of genes involved in ROS scavenging, chlorophyll biosynthesis, photosynthesis, and carbon/nitrogen balances, and downregulated expression of senescence-associated genes. Furthermore, hormone responses showed an extensively modulated expression, complemented by carotenoid biosynthesis regulation to achieve growth acceleration in melatonin-treated plants upon exposure to dehydration stress. These findings may provide more comprehensive insights into the role of melatonin in alleviating leaf senescence and enhancing dehydration resistance."
Authors: Na Li, Cunpei Bo, Yuanyuan Zhang and Lei Wang.
Journal of Experimental Botany (2021)
Abstract: "Leaf senescence can be triggered by multiple abiotic stresses including dark, nutrient limitation, salinity and drought. Recently, heat waves occurred more often than ever, which dramatically affect plant growth and development. However, the underlying molecular networks of heat stress-induced leaf senescence remain largely uncharacterized. Here we showed that PHYTOCHROME INTERACTING FACTOR 4 (PIF4) and PIF5 proteins could efficiently promote heat stress-induced leaf senescence in Arabidopsis. Transcriptomic profiling analysis revealed that PIF4 and PIF5 function likely through multiple biological processes including hormone signaling pathways. Further, we characterized NAC019, SAG113 and IAA29 as direct transcriptional targets of PIF4 and PIF5. The transcriptional expression of the NAC019, SAG113 and IAA29 changes significantly in daytime after heat treatment. In addition, we demonstrated that PIF4 and PIF5 proteins were accumulated during the recovery after heat treatment. Moreover, we showed that heat stress-induced leaf senescence is gated by circadian clock, and plants might be more actively responsive to heat stress-induced senescence during the day. Taken together, our findings proposed important roles of PIF4 and PIF5 in mediating heat stress-induced leaf senescence, which may benefit to fully illustrate the molecular network of heat stress-induced leaf senescence in higher plants and facilitates to generate heat stress-tolerant crops."
Authors: Tom Rankenberg, Batist Geldhof, Hans van Veen, Kristof Holsteens, Bram Van de Poel and Rashmi Sasidharan.
Trends in Plant Science (2021)
Highlights: The processes of aging, such as leaf development, senescence, and phase transitions from juvenile to adult plants, are genetically programmed and highly controlled by complex regulatory pathways. During aging, plants alter their organ morphology, sink–source balances, and chemical composition, including changes in redox status and hormone levels, which will collectively determine how abiotic stress signals are perceived and processed. The actual abiotic stress resilience of a plant organ (e.g., a leaf) is determined by the complex integration of age-related developmental factors and stress response pathways. Age-related abiotic stress resilience manifests by differential responses with respect to (i) morphological plasticity to allow stress escape or endurance; (ii) an altered tolerance toward photoinhibition and reactive oxygen species (ROS) build-up preventing oxidative damage; and (iii) a changing sensitivity toward induced senescence to facilitate resource allocation and stress survival.
Abstract: "Developmental age is a strong determinant of stress responses in plants. Differential susceptibility to various environmental stresses is widely observed at both the organ and whole-plant level. While it is clear that age determines stress susceptibility, the causes, regulatory mechanisms, and functions are only now beginning to emerge. Compared with concepts on age-related biotic stress resilience, advancements in the abiotic stress field are relatively limited. In this review, we focus on current knowledge of ontogenic resistance to abiotic stresses, highlighting examples at the organ (leaf) and plant level, preceded by an overview of the relevant concepts in plant aging. We also discuss age-related abiotic stress resilience mechanisms, speculate on their functional relevance, and outline outstanding questions."
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