Special Issue "Leaf Senescence"

A special issue of Plants (ISSN 2223-7747). This special issue belongs to the section "Plant Physiology and Metabolism".

Deadline for manuscript submissions: closed (15 October 2019).

Special Issue Editor

Prof. Dr. Ulrike Zentgraf
Website
Guest Editor
Universitat Tubingen, Centre for Plant Molecular Biology, Tubingen, Germany
Interests: senescence regulation; regulatory networks; transcription factors; oxidative stress and hydrogen peroxide as signaling molecule; leaf developmental memory

Special Issue Information

Dear Colleagues,

Senescence is the last step in leaf development and aims at remobilizing previously acquired nitrogen carbon and mineral resources out of the senescing tissue before the leaf eventually dies and is shed. Before anthesis, sequential leaf senescence leads to the repartitioning of nutrients from older leaves to newly developing non-reproductive organs. After anthesis, monocarpic leaf senescence governs nutrient reallocation to the now developing reproductive organs and, therefore, has a very critical impact on yield. In the last two decades, it has become obvious that no “master regulator” for senescence exists, but an extremely complex regulatory network controls all aspects of senescence. Leaf and plant age are the predominant parameters controlling the onset and progression of senescence; however, incoming environmental signals are constantly integrated and have the potential to induce senescence prematurely. Premature senescence serves as an exit strategy to produce offspring when biotic or abiotic stress generates long-term unfavorable conditions for the plant. However, premature senescence often correlates with diminished seed quantity and quality and has therefore high influence on productivity and yield in crop plants.

Multi-layer feedback regulatory cues are in place to control senescence, and transcriptional, post-transcriptional, post-translational regulatory mechanisms can act in concert for a single gene. Moreover, we are just beginning to understand the dynamic changes in chromatin structure and nuclear architecture during senescence. Alternative splicing and polyadenylation events have rarely been analyzed. Therefore, this Special Issue aims at collecting a wide range of different articles (original research papers, perspectives, hypotheses, opinions, reviews, modeling approaches, and methods) that focus on leaf senescence and its regulation at all levels, including biochemistry, physiology, genes, RNAs, proteins, metabolites, nutrition, and environment, in model or crop plants. In addition, comparisons of leaf senescence to senescnece processes in other plant organs or evolutionary aspects of senescence are most welcome.

Prof. Dr. Ulrike Zentgraf
Guest Editor

Manuscript Submission Information

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Keywords

  • kinetics of leaf senescence
  • sequential versus monocarpic senescence
  • ROS and phytohormone signaling
  • transcriptional networks
  • role of cellular compartments
  • nutrient repartitioning
  • alternative splicing and polyadenylation events

Published Papers (11 papers)

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Research

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Open AccessArticle
Short-Term Post-Harvest Stress that Affects Profiles of Volatile Organic Compounds and Gene Expression in Rocket Salad during Early Post-Harvest Senescence
Plants 2020, 9(1), 4; https://doi.org/10.3390/plants9010004 - 18 Dec 2019
Cited by 1
Abstract
Once harvested, leaves undergo a process of senescence which shares some features with developmental senescence. These include changes in gene expression, metabolites, and loss of photosynthetic capacity. Of particular interest in fresh produce are changes in nutrient content and the aroma, which is [...] Read more.
Once harvested, leaves undergo a process of senescence which shares some features with developmental senescence. These include changes in gene expression, metabolites, and loss of photosynthetic capacity. Of particular interest in fresh produce are changes in nutrient content and the aroma, which is dependent on the profile of volatile organic compounds (VOCs). Leafy salads are subjected to multiple stresses during and shortly after harvest, including mechanical damage, storage or transport under different temperature regimes, and low light. These are thought to impact on later shelf life performance by altering the progress of post-harvest senescence. Short term stresses in the first 24 h after harvest were simulated in wild rocket (Diplotaxis tenuifolia). These included dark (ambient temperature), dark and wounding (ambient temperature), and storage at 4 °C in darkness. The effects of stresses were monitored immediately afterwards and after one week of storage at 10 °C. Expression changes in two NAC transcription factors (orthologues of ANAC059 and ANAC019), and a gene involved in isothiocyanate production (thiocyanate methyltransferase, TMT) were evident immediately after stress treatments with some expression changes persisting following storage. Vitamin C loss and microbial growth on leaves were also affected by stress treatments. VOC profiles were differentially affected by stress treatments and the storage period. Overall, short term post-harvest stresses affected multiple aspects of rocket leaf senescence during chilled storage even after a week. However, different stress combinations elicited different responses. Full article
(This article belongs to the Special Issue Leaf Senescence)
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Open AccessArticle
Transcriptomic Analysis of Dark-Induced Senescence in Bermudagrass (Cynodon dactylon)
Plants 2019, 8(12), 614; https://doi.org/10.3390/plants8120614 - 17 Dec 2019
Abstract
Leaf senescence induced by prolonged light deficiency is inevitable whenever turfgrass is cultivated in forests, and this negatively influences the survival and aesthetic quality of the turfgrass. However, the mechanism underlying dark-induced senescence in turfgrass remained obscure. In this study, RNA sequencing was [...] Read more.
Leaf senescence induced by prolonged light deficiency is inevitable whenever turfgrass is cultivated in forests, and this negatively influences the survival and aesthetic quality of the turfgrass. However, the mechanism underlying dark-induced senescence in turfgrass remained obscure. In this study, RNA sequencing was performed to analyze how genes were regulated in response to dark-induced leaf senescence in bermudagrass. A total of 159,207 unigenes were obtained with a mean length of 948 bp. The differential expression analysis showed that a total of 59,062 genes, including 52,382 up-regulated genes and 6680 down-regulated genes were found to be differentially expressed between control leaves and senescent leaves induced by darkness. Subsequent bioinformatics analysis showed that these differentially expressed genes (DEGs) were mainly related to plant hormone (ethylene, abscisic acid, jasmonic acid, auxin, cytokinin, gibberellin, and brassinosteroid) signal transduction, N-glycan biosynthesis, and protein processing in the endoplasmic reticulum. In addition, transcription factors, such as WRKY, NAC, HSF, and bHLH families were also responsive to dark-induced leaf senescence in bermudagrass. Finally, qRT-PCR analysis of six randomly selected DEGs validated the accuracy of sequencing results. Taken together, our results provide basic information of how genes respond to darkness, and contribute to the understanding of comprehensive mechanisms of dark-induced leaf senescence in turfgrass. Full article
(This article belongs to the Special Issue Leaf Senescence)
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Open AccessArticle
Asparagine Synthesis during Tobacco Leaf Curing
Plants 2019, 8(11), 492; https://doi.org/10.3390/plants8110492 - 11 Nov 2019
Cited by 1
Abstract
Senescence is a genetically controlled mechanism that modifies leaf chemistry. This involves significant changes in the accumulation of carbon- and nitrogen-containing compounds, including asparagine through the activity of asparagine synthetases. These enzymes are required for nitrogen re-assimilation and remobilization in plants; however, their [...] Read more.
Senescence is a genetically controlled mechanism that modifies leaf chemistry. This involves significant changes in the accumulation of carbon- and nitrogen-containing compounds, including asparagine through the activity of asparagine synthetases. These enzymes are required for nitrogen re-assimilation and remobilization in plants; however, their mechanisms are not fully understood. Here, we report how leaf curing—a senescence-induced process that allows tobacco leaves to dry out—modifies the asparagine metabolism. We show that leaf curing strongly alters the concentration of the four main amino acids, asparagine, glutamine, aspartate, and glutamate. We demonstrate that detached tobacco leaf or stalk curing has a different impact on the expression of asparagine synthetase genes and accumulation of asparagine. Additionally, we characterize the main asparagine synthetases involved in the production of asparagine during curing. The expression of ASN1 and ASN5 genes is upregulated during curing. The ASN1-RNAi and ASN5-RNAi tobacco plant lines display significant alterations in the accumulation of asparagine, glutamine, and aspartate relative to wild-type plants. These results support the idea that ASN1 and ASN5 are key regulators of asparagine metabolism during leaf curing. Full article
(This article belongs to the Special Issue Leaf Senescence)
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Open AccessArticle
Exogenous Melatonin Delays Dark-Induced Grape Leaf Senescence by Regulation of Antioxidant System and Senescence Associated Genes (SAGs)
Plants 2019, 8(10), 366; https://doi.org/10.3390/plants8100366 - 23 Sep 2019
Cited by 5
Abstract
Leaf senescence is a developmentally programmed and degenerative process which comprises the last stage of the life cycle of leaves. In order to understand the melatonin effect on grapevine leaf senescence, the dark treatment on detached leaves of Vitis vinifera L. cv. Red [...] Read more.
Leaf senescence is a developmentally programmed and degenerative process which comprises the last stage of the life cycle of leaves. In order to understand the melatonin effect on grapevine leaf senescence, the dark treatment on detached leaves of Vitis vinifera L. cv. Red Globe was performed to induce leaf senescence at short period of time. Then, a series of physiological and molecular changes in response to exogenous melatonin were measured. Results showed that 100 μM of melatonin treatment could significantly delay the dark induced leaf senescence, which is accompanied by the decreased production of reactive oxygen species (ROS). Meanwhile, melatonin treatment could increase the scavenging activity of antioxidant enzymes, such as peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT). Simultaneously, ascorbate (AsA) and glutathione (GSH) contents, the activities of ascorbate peroxidase (APX), and glutathione reductase (GR) were significantly higher than control treatment in samples treated with melatonin. Furthermore, melatonin treatment showed to suppress the expression of leaf senescence-associated genes (SAGs). All these results demonstrated that melatonin could activate the antioxidant and Ascorbate-Glutathione (AsA-GSH) cycle system and repress the expression of SAGs that lead to delay the dark induced grape leaf senescence. Full article
(This article belongs to the Special Issue Leaf Senescence)
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Open AccessArticle
Expression of Genes Related to Sugar and Amino Acid Transport and Cytokinin Metabolism during Leaf Development and Senescence in Pisum sativum L.
Plants 2019, 8(3), 76; https://doi.org/10.3390/plants8030076 - 25 Mar 2019
Cited by 1
Abstract
Gene editing is becoming the plant breeding tool of choice, but prior to targeting a gene for editing, a knowledge of the gene family members (GFMs) controlling yield is required in the specific crop plant. Critical to yield are components from senescing leaves. [...] Read more.
Gene editing is becoming the plant breeding tool of choice, but prior to targeting a gene for editing, a knowledge of the gene family members (GFMs) controlling yield is required in the specific crop plant. Critical to yield are components from senescing leaves. We targeted genes controlling senescence in Pisum sativum and the release and transport of carbohydrates and amino acids from the source leaves to the pods and seeds. The expression of GFMs for cytokinin biosynthesis (IPT) and destruction (CKX), sucrose transporters (SUT), Sugar Will Eventually be Exported Transporters (SWEET), amino acid permeases (AAP), and cell wall invertases, was determined using RT-qPCR. GFMs were differentially expressed in leaves of different ages. The expression of many gene family members was lower in the expanding sink leaves compared with the senescing leaves, with the exception of two PsAAP GFMs and PsCKX5, which were highly expressed. Expression of specific PsSWEETs, SUTs, and AAPs increased in the mature and/or senescing leaves. Expression of PsIPTs was least in the mature source leaves, but as strong in the senescing leaves as in the young source leaves. PsCKX7 was expressed in source and senescing leaves. We discuss the potential impact of the targeted reduction of specific PsCKX GFMs on source-sink relationships. Full article
(This article belongs to the Special Issue Leaf Senescence)
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Review

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Open AccessReview
Genetic Network between Leaf Senescence and Plant Immunity: Crucial Regulatory Nodes and New Insights
Plants 2020, 9(4), 495; https://doi.org/10.3390/plants9040495 - 13 Apr 2020
Cited by 2
Abstract
Leaf senescence is an essential physiological process that is accompanied by the remobilization of nutrients from senescent leaves to young leaves or other developing organs. Although leaf senescence is a genetically programmed process, it can be induced by a wide variety of biotic [...] Read more.
Leaf senescence is an essential physiological process that is accompanied by the remobilization of nutrients from senescent leaves to young leaves or other developing organs. Although leaf senescence is a genetically programmed process, it can be induced by a wide variety of biotic and abiotic factors. Accumulating studies demonstrate that senescence-associated transcription factors (Sen-TFs) play key regulatory roles in controlling the initiation and progression of leaf senescence process. Interestingly, recent functional studies also reveal that a number of Sen-TFs function as positive or negative regulators of plant immunity. Moreover, the plant hormone salicylic acid (SA) and reactive oxygen species (ROS) have been demonstrated to be key signaling molecules in regulating leaf senescence and plant immunity, suggesting that these two processes share similar or common regulatory networks. However, the interactions between leaf senescence and plant immunity did not attract sufficient attention to plant scientists. Here, we review the regulatory roles of SA and ROS in biotic and abiotic stresses, as well as the cross-talks between SA/ROS and other hormones in leaf senescence and plant immunity, summarize the transcriptional controls of Sen-TFs on SA and ROS signal pathways, and analyze the cross-regulation between senescence and immunity through a broad literature survey. In-depth understandings of the cross-regulatory mechanisms between leaf senescence and plant immunity will facilitate the cultivation of high-yield and disease-resistant crops through a molecular breeding strategy. Full article
(This article belongs to the Special Issue Leaf Senescence)
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Open AccessReview
Arabidopsis WRKY53, a Node of Multi-Layer Regulation in the Network of Senescence
Plants 2019, 8(12), 578; https://doi.org/10.3390/plants8120578 - 06 Dec 2019
Cited by 4
Abstract
Leaf senescence is an integral part of plant development aiming at the remobilization of nutrients and minerals out of the senescing tissue into developing parts of the plant. Sequential as well as monocarpic senescence maximize the usage of nitrogen, mineral, and carbon resources [...] Read more.
Leaf senescence is an integral part of plant development aiming at the remobilization of nutrients and minerals out of the senescing tissue into developing parts of the plant. Sequential as well as monocarpic senescence maximize the usage of nitrogen, mineral, and carbon resources for plant growth and the sake of the next generation. However, stress-induced premature senescence functions as an exit strategy to guarantee offspring under long-lasting unfavorable conditions. In order to coordinate this complex developmental program with all kinds of environmental input signals, complex regulatory cues have to be in place. Major changes in the transcriptome imply important roles for transcription factors. Among all transcription factor families in plants, the NAC and WRKY factors appear to play central roles in senescence regulation. In this review, we summarize the current knowledge on the role of WRKY factors with a special focus on WRKY53. In contrast to a holistic multi-omics view we want to exemplify the complexity of the network structure by summarizing the multilayer regulation of WRKY53 of Arabidopsis. Full article
(This article belongs to the Special Issue Leaf Senescence)
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Open AccessReview
Leaf Senescence: The Chloroplast Connection Comes of Age
Plants 2019, 8(11), 495; https://doi.org/10.3390/plants8110495 - 12 Nov 2019
Cited by 1
Abstract
Leaf senescence is a developmental process critical for plant fitness, which involves genetically controlled cell death and ordered disassembly of macromolecules for reallocating nutrients to juvenile and reproductive organs. While natural leaf senescence is primarily associated with aging, it can also be induced [...] Read more.
Leaf senescence is a developmental process critical for plant fitness, which involves genetically controlled cell death and ordered disassembly of macromolecules for reallocating nutrients to juvenile and reproductive organs. While natural leaf senescence is primarily associated with aging, it can also be induced by environmental and nutritional inputs including biotic and abiotic stresses, darkness, phytohormones and oxidants. Reactive oxygen species (ROS) are a common thread in stress-dependent cell death and also increase during leaf senescence. Involvement of chloroplast redox chemistry (including ROS propagation) in modulating cell death is well supported, with photosynthesis playing a crucial role in providing redox-based signals to this process. While chloroplast contribution to senescence received less attention, recent findings indicate that changes in the redox poise of these organelles strongly affect senescence timing and progress. In this review, the involvement of chloroplasts in leaf senescence execution is critically assessed in relation to available evidence and the role played by environmental and developmental cues such as stress and phytohormones. The collected results indicate that chloroplasts could cooperate with other redox sources (e.g., mitochondria) and signaling molecules to initiate the committed steps of leaf senescence for a best use of the recycled nutrients in plant reproduction. Full article
(This article belongs to the Special Issue Leaf Senescence)
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Open AccessReview
New Aspects of HECT-E3 Ligases in Cell Senescence and Cell Death of Plants
Plants 2019, 8(11), 483; https://doi.org/10.3390/plants8110483 - 08 Nov 2019
Abstract
Plant cells undergo massive orderly changes in structure, biochemistry, and gene expression during cell senescence. These changes cannot be distinguished from the hydrolysis/degradation function controlled by the ubiquitination pathway, autophagy, and various hydrolases in cells. In this mini-review, we summarized current research progress [...] Read more.
Plant cells undergo massive orderly changes in structure, biochemistry, and gene expression during cell senescence. These changes cannot be distinguished from the hydrolysis/degradation function controlled by the ubiquitination pathway, autophagy, and various hydrolases in cells. In this mini-review, we summarized current research progress that the human HECT (homologous to the E6AP carboxyl terminus)-type ubiquitin E3 ligases have non-redundant functions in regulating specific signaling pathways, involved in a number of human diseases, especially aging-related diseases, through the influence of DNA repair, protein stability, and removal efficiency of damaged proteins or organelles. We further compared HECT E3 ligases’ structure and functions between plant and mammalian cells, and speculated new aspects acting as degrading signals and regulating signals of HECT E3 ligase in cell senescence and the cell death of plants. Full article
(This article belongs to the Special Issue Leaf Senescence)
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Open AccessReview
Transcription Factors Associated with Leaf Senescence in Crops
Plants 2019, 8(10), 411; https://doi.org/10.3390/plants8100411 - 14 Oct 2019
Cited by 9
Abstract
Leaf senescence is a complex mechanism controlled by multiple genetic and environmental variables. Different crops present a delay in leaf senescence with an important impact on grain yield trough the maintenance of the photosynthetic leaf area during the reproductive stage. Additionally, because of [...] Read more.
Leaf senescence is a complex mechanism controlled by multiple genetic and environmental variables. Different crops present a delay in leaf senescence with an important impact on grain yield trough the maintenance of the photosynthetic leaf area during the reproductive stage. Additionally, because of the temporal gap between the onset and phenotypic detection of the senescence process, candidate genes are key tools to enable the early detection of this process. In this sense and given the importance of some transcription factors as hub genes in senescence pathways, we present a comprehensive review on senescence-associated transcription factors, in model plant species and in agronomic relevant crops. This review will contribute to the knowledge of leaf senescence process in crops, thus providing a valuable tool to assist molecular crop breeding. Full article
(This article belongs to the Special Issue Leaf Senescence)
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Open AccessReview
Signal Transduction in Leaf Senescence: Progress and Perspective
Plants 2019, 8(10), 405; https://doi.org/10.3390/plants8100405 - 10 Oct 2019
Cited by 1
Abstract
Leaf senescence is a degenerative process that is genetically controlled and involves nutrient remobilization prior to the death of leaf tissues. Age is a key developmental determinant of the process along with other senescence inducing factors. At the cellular level, different hormones, signaling [...] Read more.
Leaf senescence is a degenerative process that is genetically controlled and involves nutrient remobilization prior to the death of leaf tissues. Age is a key developmental determinant of the process along with other senescence inducing factors. At the cellular level, different hormones, signaling molecules, and transcription factors contribute to the regulation of senescence. This review summarizes the recent progress in understanding the complexity of the senescence process with primary focuses on perception and transduction of senescence signals as well as downstream regulatory events. Future directions in this field and potential applications of related techniques in crop improvement will be discussed. Full article
(This article belongs to the Special Issue Leaf Senescence)
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