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Plant Senescence
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Plant Senescence

A special issue of Plants (ISSN 2223-7747).

Deadline for manuscript submissions: closed (31 May 2015) | Viewed by 161626

Special Issue Editor

Dr. Salma Balazadeh

E-Mail Website1 Website2
Guest Editor
Institute of Molecular Plant Physiology, University of Potsdam and Max-Planck, Potsdam-Golm, Germany
Interests: transcription factors (TFs), gene regulatory networks (GRNs), leaf growth, senescence, abiotic stress, priming and memory

Special Issue Information

Dear Colleagues,

Leaf senescence is the final stage in leaf development and is a highly regulated, systematic process with a great impact on yield, biomass and nitrogen partitioning. During senescence, nutrients are mobilized from photosynthetically inefficient leaves to actively growing organs including young leaves and seeds. Thus senescence is a process that supports whole-plant development. Although developmental age is the primary factor mediating the initiation and progression of leaf senescence, additional factors such as environmental parameters and abiotic stresses can alter the timing of the senescence process to a great extent. Both types of senescence, developmental and stress-induced, are mediated by signaling molecules including phytohormones (e.g., ethylene and ABA) and reactive oxygen species (ROS), among others, and involve the action of transcription factors (TFs) that regulate target genes and altogether establish gene regulatory networks (GRNs). Besides leaves, other organs, such as flowers, fruits and roots, eventually undergo senescence which affects the whole-plant nutrient economy and developmental patterns.

During the past decade, much attention has been directed towards understanding the molecular mechanisms underlying senescence of leaves and other organs. This Special Issue is aimed at establishing a wide collection of articles (original research papers, hypotheses, opinions, reviews, modeling approaches and methods) that focus on the process of senescence at different levels of biological organization, from individual cells to entire plants. We are particularly interested in receiving contributions that address regulation of leaf and organ senescence from various layers, such as the epigenome, transcriptome, proteome and metabolome in dicot or monocot species. Additionally, articles addressing evolution of senescence are highly welcome.

Dr. Salma Balazadeh
Guest Editor

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Keywords

  • leaf senescence;
  • abiotic stress;
  • photosynthesis;
  • nutrient remobilization;
  • yield;
  • transcription factors;
  • gene regulatory networks (GRNs)

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Published Papers (14 papers)

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1888 KiB  
Article
Knockdown of WHIRLY1 Affects Drought Stress-Induced Leaf Senescence and Histone Modifications of the Senescence-Associated Gene HvS40
by Bianka Janack, Paula Sosoi, Karin Krupinska and Klaus Humbeck
Plants 2016, 5(3), 37; https://doi.org/10.3390/plants5030037 - 6 Sep 2016
Cited by 38 | Viewed by 7879
Abstract
The plastid-nucleus located protein WHIRLY1 has been described as an upstream regulator of leaf senescence, binding to the promoter of senescence-associated genes like HvS40. To investigate the impact of WHIRLY1 on drought stress-induced, premature senescence, transgenic barley plants with an RNAi-mediated knockdown [...] Read more.
The plastid-nucleus located protein WHIRLY1 has been described as an upstream regulator of leaf senescence, binding to the promoter of senescence-associated genes like HvS40. To investigate the impact of WHIRLY1 on drought stress-induced, premature senescence, transgenic barley plants with an RNAi-mediated knockdown of the HvWHIRLY1 gene were grown under normal and drought stress conditions. The course of leaf senescence in these lines was monitored by physiological parameters and studies on the expression of senescence- and drought stress-related genes. Drought treatment accelerated leaf senescence in WT plants, whereas WHIRLY 1 knockdown lines (RNAi-W1) showed a stay-green phenotype. Expression of both senescence-associated and drought stress-responsive genes, was delayed in the transgenic plants. Notably, expression of transcription factors of the WRKY and NAC families, which are known to function in senescence- and stress-related signaling pathways, was affected in plants with impaired accumulation of WHIRLY1, indicating that WHIRLY1 acts as an upstream regulator of drought stress-induced senescence. To reveal the epigenetic indexing of HvS40 at the onset of drought-induced senescence in WT and RNAi-W1 lines, stress-responsive loading with histone modifications of promoter and coding sequences of HvS40 was analyzed by chromatin immunoprecipitation and quantified by qRT-PCR. In the wildtype, the euchromatic mark H3K9ac of the HvS40 gene was low under control conditions and was established in response to drought treatment, indicating the action of epigenetic mechanisms in response to drought stress. However, drought stress caused no significant increase in H3K9ac in plants impaired in accumulation of WHIRLY1. The results show that WHIRLY1 knockdown sets in motion a delay in senescence that involves all aspects of gene expression, including changes in chromatin structure. Full article
(This article belongs to the Special Issue Plant Senescence)
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1783 KiB  
Article
A Comparative Study of Proteolytic Mechanisms during Leaf Senescence of Four Genotypes of Winter Oilseed Rape Highlighted Relevant Physiological and Molecular Traits for NRE Improvement
by Alexandra Girondé, Marine Poret, Philippe Etienne, Jacques Trouverie, Alain Bouchereau, Françoise Le Cahérec, Laurent Leport, Marie-Françoise Niogret and Jean-Christophe Avice
Plants 2016, 5(1), 1; https://doi.org/10.3390/plants5010001 - 22 Dec 2015
Cited by 10 | Viewed by 6165
Abstract
Winter oilseed rape is characterized by a low N use efficiency related to a weak leaf N remobilization efficiency (NRE) at vegetative stages. By investigating the natural genotypic variability of leaf NRE, our goal was to characterize the relevant physiological traits and the [...] Read more.
Winter oilseed rape is characterized by a low N use efficiency related to a weak leaf N remobilization efficiency (NRE) at vegetative stages. By investigating the natural genotypic variability of leaf NRE, our goal was to characterize the relevant physiological traits and the main protease classes associated with an efficient proteolysis and high leaf NRE in response to ample or restricted nitrate supply. The degradation rate of soluble proteins and D1 protein (a thylakoid-bound protein) were correlated to N remobilization, except for the genotype Samouraï which showed a low NRE despite high levels of proteolysis. Under restricted nitrate conditions, high levels of soluble protein degradation were associated with serine, cysteine and aspartic proteases at acidic pH. Low leaf NRE was related to a weak proteolysis of both soluble and thylakoid-bound proteins. The results obtained on the genotype Samouraï suggest that the timing between the onset of proteolysis and abscission could be a determinant. The specific involvement of acidic proteases suggests that autophagy and/or senescence-associated vacuoles are implicated in N remobilization under low N conditions. The data revealed that the rate of D1 degradation could be a relevant indicator of leaf NRE and might be used as a tool for plant breeding. Full article
(This article belongs to the Special Issue Plant Senescence)
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581 KiB  
Review
Molecular Mechanisms of Phosphorus Metabolism and Transport during Leaf Senescence
by Kyla A. Stigter and William C. Plaxton
Plants 2015, 4(4), 773-798; https://doi.org/10.3390/plants4040773 - 16 Dec 2015
Cited by 96 | Viewed by 11437
Abstract
Leaf senescence, being the final developmental stage of the leaf, signifies the transition from a mature, photosynthetically active organ to the attenuation of said function and eventual death of the leaf. During senescence, essential nutrients sequestered in the leaf, such as phosphorus (P), [...] Read more.
Leaf senescence, being the final developmental stage of the leaf, signifies the transition from a mature, photosynthetically active organ to the attenuation of said function and eventual death of the leaf. During senescence, essential nutrients sequestered in the leaf, such as phosphorus (P), are mobilized and transported to sink tissues, particularly expanding leaves and developing seeds. Phosphorus recycling is crucial, as it helps to ensure that previously acquired P is not lost to the environment, particularly under the naturally occurring condition where most unfertilized soils contain low levels of soluble orthophosphate (Pi), the only form of P that roots can directly assimilate from the soil. Piecing together the molecular mechanisms that underpin the highly variable efficiencies of P remobilization from senescing leaves by different plant species may be critical for devising effective strategies for improving overall crop P-use efficiency. Maximizing Pi remobilization from senescing leaves using selective breeding and/or biotechnological strategies will help to generate P-efficient crops that would minimize the use of unsustainable and polluting Pi-containing fertilizers in agriculture. This review focuses on the molecular mechanisms whereby P is remobilized from senescing leaves and transported to sink tissues, which encompasses the action of hormones, transcription factors, Pi-scavenging enzymes, and Pi transporters. Full article
(This article belongs to the Special Issue Plant Senescence)
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794 KiB  
Review
Leaf Senescence by Magnesium Deficiency
by Keitaro Tanoi and Natsuko I. Kobayashi
Plants 2015, 4(4), 756-772; https://doi.org/10.3390/plants4040756 - 11 Dec 2015
Cited by 74 | Viewed by 11972
Abstract
Magnesium ions (Mg2+) are the second most abundant cations in living plant cells, and they are involved in various functions, including photosynthesis, enzyme catalysis, and nucleic acid synthesis. Low availability of Mg2+ in an agricultural field leads to a decrease [...] Read more.
Magnesium ions (Mg2+) are the second most abundant cations in living plant cells, and they are involved in various functions, including photosynthesis, enzyme catalysis, and nucleic acid synthesis. Low availability of Mg2+ in an agricultural field leads to a decrease in yield, which follows the appearance of Mg-deficient symptoms such as chlorosis, necrotic spots on the leaves, and droop. During the last decade, a variety of physiological and molecular responses to Mg2+ deficiency that potentially link to leaf senescence have been recognized, allowing us to reconsider the mechanisms of Mg2+ deficiency. This review focuses on the current knowledge about the physiological responses to Mg2+ deficiency including a decline in transpiration, accumulation of sugars and starch in source leaves, change in redox states, increased oxidative stress, metabolite alterations, and a decline in photosynthetic activity. In addition, we refer to the molecular responses that are thought to be related to leaf senescence. With these current data, we give an overview of leaf senescence induced by Mg deficiency. Full article
(This article belongs to the Special Issue Plant Senescence)
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1441 KiB  
Article
Phosphorylation Affects DNA-Binding of the Senescence-Regulating bZIP Transcription Factor GBF1
by Anja Smykowski, Stefan M. Fischer and Ulrike Zentgraf
Plants 2015, 4(3), 691-709; https://doi.org/10.3390/plants4030691 - 16 Sep 2015
Cited by 18 | Viewed by 7679 | Correction
Abstract
Massive changes in the transcriptome of Arabidopsis thaliana during onset and progression of leaf senescence imply a central role for transcription factors. While many transcription factors are themselves up- or down-regulated during senescence, the bZIP transcription factor G-box-binding factor 1 (GBF1/bZIP41) is constitutively [...] Read more.
Massive changes in the transcriptome of Arabidopsis thaliana during onset and progression of leaf senescence imply a central role for transcription factors. While many transcription factors are themselves up- or down-regulated during senescence, the bZIP transcription factor G-box-binding factor 1 (GBF1/bZIP41) is constitutively expressed in Arabidopsis leaf tissue but at the same time triggers the onset of leaf senescence, suggesting posttranscriptional mechanisms for senescence-specific GBF1 activation. Here we show that GBF1 is phosphorylated by the threonine/serine CASEIN KINASE II (CKII) in vitro and that CKII phosphorylation had a negative effect on GBF1 DNA-binding to G-boxes of two direct target genes, CATALASE2 and RBSCS1a. Phosphorylation mimicry at three serine positions in the basic region of GBF1 also had a negative effect on DNA-binding. Kinase assays revealed that CKII phosphorylates at least one serine in the basic domain but has additional phosphorylation sites outside this domain. Two different ckII α subunit1 and one α subunit2 T-DNA insertion lines showed no visible senescence phenotype, but in all lines the expression of the senescence marker gene SAG12 was remarkably diminished. A model is presented suggesting that senescence-specific GBF1 activation might be achieved by lowering the phosphorylation of GBF1 by CKII. Full article
(This article belongs to the Special Issue Plant Senescence)
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830 KiB  
Article
Green Leaf Volatile Emissions during High Temperature and Drought Stress in a Central Amazon Rainforest
by Kolby J. Jardine, Jeffrey Q. Chambers, Jennifer Holm, Angela B. Jardine, Clarissa G. Fontes, Raquel F. Zorzanelli, Kimberly T. Meyers, Vinicius Fernadez De Souza, Sabrina Garcia, Bruno O. Gimenez, Luani R. de O. Piva, Niro Higuchi, Paulo Artaxo, Scot Martin and Antônio O. Manzi
Plants 2015, 4(3), 678-690; https://doi.org/10.3390/plants4030678 - 15 Sep 2015
Cited by 49 | Viewed by 14347
Abstract
Prolonged drought stress combined with high leaf temperatures can induce programmed leaf senescence involving lipid peroxidation, and the loss of net carbon assimilation during early stages of tree mortality. Periodic droughts are known to induce widespread tree mortality in the Amazon rainforest, but [...] Read more.
Prolonged drought stress combined with high leaf temperatures can induce programmed leaf senescence involving lipid peroxidation, and the loss of net carbon assimilation during early stages of tree mortality. Periodic droughts are known to induce widespread tree mortality in the Amazon rainforest, but little is known about the role of lipid peroxidation during drought-induced leaf senescence. In this study, we present observations of green leaf volatile (GLV) emissions during membrane peroxidation processes associated with the combined effects of high leaf temperatures and drought-induced leaf senescence from individual detached leaves and a rainforest ecosystem in the central Amazon. Temperature-dependent leaf emissions of volatile terpenoids were observed during the morning, and together with transpiration and net photosynthesis, showed a post-midday depression. This post-midday depression was associated with a stimulation of C5 and C6 GLV emissions, which continued to increase throughout the late afternoon in a temperature-independent fashion. During the 2010 drought in the Amazon Basin, which resulted in widespread tree mortality, green leaf volatile emissions (C6 GLVs) were observed to build up within the forest canopy atmosphere, likely associated with high leaf temperatures and enhanced drought-induced leaf senescence processes. The results suggest that observations of GLVs in the tropical boundary layer could be used as a chemical sensor of reduced ecosystem productivity associated with drought stress. Full article
(This article belongs to the Special Issue Plant Senescence)
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624 KiB  
Review
Possible Roles of Strigolactones during Leaf Senescence
by Yusuke Yamada and Mikihisa Umehara
Plants 2015, 4(3), 664-677; https://doi.org/10.3390/plants4030664 - 11 Sep 2015
Cited by 56 | Viewed by 10661
Abstract
Leaf senescence is a complicated developmental process that involves degenerative changes and nutrient recycling. The progress of leaf senescence is controlled by various environmental cues and plant hormones, including ethylene, jasmonic acid, salicylic acid, abscisic acid, cytokinins, and strigolactones. The production of strigolactones [...] Read more.
Leaf senescence is a complicated developmental process that involves degenerative changes and nutrient recycling. The progress of leaf senescence is controlled by various environmental cues and plant hormones, including ethylene, jasmonic acid, salicylic acid, abscisic acid, cytokinins, and strigolactones. The production of strigolactones is induced in response to nitrogen and phosphorous deficiency. Strigolactones also accelerate leaf senescence and regulate shoot branching and root architecture. Leaf senescence is actively promoted in a nutrient-poor soil environment, and nutrients are transported from old leaves to young tissues and seeds. Strigolactones might act as important signals in response to nutrient levels in the rhizosphere. In this review, we discuss the possible roles of strigolactones during leaf senescence. Full article
(This article belongs to the Special Issue Plant Senescence)
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1423 KiB  
Article
Rice Phytochrome B (OsPhyB) Negatively Regulates Dark- and Starvation-Induced Leaf Senescence
by Weilan Piao, Eun-Young Kim, Su-Hyun Han, Yasuhito Sakuraba and Nam-Chon Paek
Plants 2015, 4(3), 644-663; https://doi.org/10.3390/plants4030644 - 1 Sep 2015
Cited by 29 | Viewed by 9740
Abstract
Light regulates leaf senescence and light deprivation causes large-scale transcriptional reprogramming to dismantle cellular components and remobilize nutrients to sink organs, such as seeds and storage tissue. We recently reported that in Arabidopsis (Arabidopsis thaliana), Phytochrome-Interacting Factor4 (PIF4) and PIF5 promote [...] Read more.
Light regulates leaf senescence and light deprivation causes large-scale transcriptional reprogramming to dismantle cellular components and remobilize nutrients to sink organs, such as seeds and storage tissue. We recently reported that in Arabidopsis (Arabidopsis thaliana), Phytochrome-Interacting Factor4 (PIF4) and PIF5 promote dark-induced senescence and natural senescence by directly activating the expression of typical senescence-associated genes (SAGs), including ORESARA1 (ORE1) and ETHYLENE INSENSITIVE3 (EIN3). In contrast, phytochrome B (PhyB) inhibits leaf senescence by repressing PIF4 and PIF5 at the post-translational level. Although we found how red light signaling represses leaf senescence in Arabidopsis, it remains unknown whether PhyB and/or PhyA are involved in leaf senescence in rice (Oryza sativa). Here we show that rice phyB knockout mutants (osphyB-1, -2, and -3) exhibited an early senescence phenotype during dark-induced senescence, but an osphyA knockout mutant (osphyA-3) senesced normally. The RT-qPCR analysis revealed that several senescence-associated genes, including OsORE1 and OsEIN3, were significantly up-regulated in osphyB-2 mutants, indicating that OsPhyB also inhibits leaf senescence, like Arabidopsis PhyB. We also found that leaf segments of osphyB-2 senesced faster even under light conditions. Supplementation with nitrogen compounds, such as KNO3 and NH4NO3, rescued the early senescence phenotype of osphyB-2, indicating that starvation is one of the major signaling factors in the OsPhyB-dependent leaf senescence pathway. Full article
(This article belongs to the Special Issue Plant Senescence)
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1252 KiB  
Article
Sulfite Oxidase Activity Is Essential for Normal Sulfur, Nitrogen and Carbon Metabolism in Tomato Leaves
by Galina Brychkova, Dmitry Yarmolinsky, Albert Batushansky, Vladislav Grishkevich, Inna Khozin-Goldberg, Aaron Fait, Rachel Amir, Robert Fluhr and Moshe Sagi
Plants 2015, 4(3), 573-605; https://doi.org/10.3390/plants4030573 - 14 Aug 2015
Cited by 17 | Viewed by 9700
Abstract
Plant sulfite oxidase [SO; E.C.1.8.3.1] has been shown to be a key player in protecting plants against exogenous toxic sulfite. Recently we showed that SO activity is essential to cope with rising dark-induced endogenous sulfite levels in tomato plants (Lycopersicon esculentum/Solanum lycopersicum [...] Read more.
Plant sulfite oxidase [SO; E.C.1.8.3.1] has been shown to be a key player in protecting plants against exogenous toxic sulfite. Recently we showed that SO activity is essential to cope with rising dark-induced endogenous sulfite levels in tomato plants (Lycopersicon esculentum/Solanum lycopersicum Mill. cv. Rheinlands Ruhm). Here we uncover the ramifications of SO impairment on carbon, nitrogen and sulfur (S) metabolites. Current analysis of the wild-type and SO-impaired plants revealed that under controlled conditions, the imbalanced sulfite level resulting from SO impairment conferred a metabolic shift towards elevated reduced S-compounds, namely sulfide, S-amino acids (S-AA), Co-A and acetyl-CoA, followed by non-S-AA, nitrogen and carbon metabolite enhancement, including polar lipids. Exposing plants to dark-induced carbon starvation resulted in a higher degradation of S-compounds, total AA, carbohydrates, polar lipids and total RNA in the mutant plants. Significantly, a failure to balance the carbon backbones was evident in the mutants, indicated by an increase in tricarboxylic acid cycle (TCA) cycle intermediates, whereas a decrease was shown in stressed wild-type plants. These results indicate that the role of SO is not limited to a rescue reaction under elevated sulfite, but SO is a key player in maintaining optimal carbon, nitrogen and sulfur metabolism in tomato plants. Full article
(This article belongs to the Special Issue Plant Senescence)
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1306 KiB  
Article
Early Autumn Senescence in Red Maple (Acer rubrum L.) Is Associated with High Leaf Anthocyanin Content
by Rachel Anderson and Peter Ryser
Plants 2015, 4(3), 505-522; https://doi.org/10.3390/plants4030505 - 5 Aug 2015
Cited by 21 | Viewed by 10323
Abstract
Several theories exist about the role of anthocyanins in senescing leaves. To elucidate factors contributing to variation in autumn leaf anthocyanin contents among individual trees, we analysed anthocyanins and other leaf traits in 27 individuals of red maple (Acer rubrum L.) over [...] Read more.
Several theories exist about the role of anthocyanins in senescing leaves. To elucidate factors contributing to variation in autumn leaf anthocyanin contents among individual trees, we analysed anthocyanins and other leaf traits in 27 individuals of red maple (Acer rubrum L.) over two growing seasons in the context of timing of leaf senescence. Red maple usually turns bright red in the autumn, but there is considerable variation among the trees. Leaf autumn anthocyanin contents were consistent between the two years of investigation. Autumn anthocyanin content strongly correlated with degree of chlorophyll degradation mid to late September, early senescing leaves having the highest concentrations of anthocyanins. It also correlated positively with leaf summer chlorophyll content and dry matter content, and negatively with specific leaf area. Time of leaf senescence and anthocyanin contents correlated with soil pH and with canopy openness. We conclude that the importance of anthocyanins in protection of leaf processes during senescence depends on the time of senescence. Rather than prolonging the growing season by enabling a delayed senescence, autumn anthocyanins in red maple in Ontario are important when senescence happens early, possibly due to the higher irradiance and greater danger of oxidative damage early in the season. Full article
(This article belongs to the Special Issue Plant Senescence)
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808 KiB  
Review
Keeping Control: The Role of Senescence and Development in Plant Pathogenesis and Defense
by Eva Häffner, Sandra Konietzki and Elke Diederichsen
Plants 2015, 4(3), 449-488; https://doi.org/10.3390/plants4030449 - 13 Jul 2015
Cited by 67 | Viewed by 11706
Abstract
Many plant pathogens show interactions with host development. Pathogens may modify plant development according to their nutritional demands. Conversely, plant development influences pathogen growth. Biotrophic pathogens often delay senescence to keep host cells alive, and resistance is achieved by senescence-like processes in the [...] Read more.
Many plant pathogens show interactions with host development. Pathogens may modify plant development according to their nutritional demands. Conversely, plant development influences pathogen growth. Biotrophic pathogens often delay senescence to keep host cells alive, and resistance is achieved by senescence-like processes in the host. Necrotrophic pathogens promote senescence in the host, and preventing early senescence is a resistance strategy of plants. For hemibiotrophic pathogens both patterns may apply. Most signaling pathways are involved in both developmental and defense reactions. Increasing knowledge about the molecular components allows to distinguish signaling branches, cross-talk and regulatory nodes that may influence the outcome of an infection. In this review, recent reports on major molecular players and their role in senescence and in pathogen response are reviewed. Examples of pathosystems with strong developmental implications illustrate the molecular basis of selected control strategies. A study of gene expression in the interaction between the hemibiotrophic vascular pathogen Verticillium longisporum and its cruciferous hosts shows processes that are fine-tuned to counteract early senescence and to achieve resistance. The complexity of the processes involved reflects the complex genetic control of quantitative disease resistance, and understanding the relationship between disease, development and resistance will support resistance breeding. Full article
(This article belongs to the Special Issue Plant Senescence)
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1381 KiB  
Review
NAC Transcription Factors in Senescence: From Molecular Structure to Function in Crops
by Dagmara Podzimska-Sroka, Charlotte O'Shea, Per L. Gregersen and Karen Skriver
Plants 2015, 4(3), 412-448; https://doi.org/10.3390/plants4030412 - 13 Jul 2015
Cited by 106 | Viewed by 15184
Abstract
Within the last decade, NAC transcription factors have been shown to play essential roles in senescence, which is the focus of this review. Transcriptome analyses associate approximately one third of Arabidopsis NAC genes and many crop NAC genes with senescence, thereby implicating NAC [...] Read more.
Within the last decade, NAC transcription factors have been shown to play essential roles in senescence, which is the focus of this review. Transcriptome analyses associate approximately one third of Arabidopsis NAC genes and many crop NAC genes with senescence, thereby implicating NAC genes as important regulators of the senescence process. The consensus DNA binding site of the NAC domain is used to predict NAC target genes, and protein interaction sites can be predicted for the intrinsically disordered transcription regulatory domains of NAC proteins. The molecular characteristics of these domains determine the interactions in gene regulatory networks. Emerging local NAC-centered gene regulatory networks reveal complex molecular mechanisms of stress- and hormone-regulated senescence and basic physiological steps of the senescence process. For example, through molecular interactions involving the hormone abscisic acid, Arabidopsis NAP promotes chlorophyll degradation, a hallmark of senescence. Furthermore, studies of the functional rice ortholog, OsNAP, suggest that NAC genes can be targeted to obtain specific changes in lifespan control and nutrient remobilization in crop plants. This is also exemplified by the wheat NAM1 genes which promote senescence and increase grain zinc, iron, and protein content. Thus, NAC genes are promising targets for fine-tuning senescence for increased yield and quality. Full article
(This article belongs to the Special Issue Plant Senescence)
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689 KiB  
Review
Senescence, Stress, and Reactive Oxygen Species
by Ivan Jajic, Tadeusz Sarna and Kazimierz Strzalka
Plants 2015, 4(3), 393-411; https://doi.org/10.3390/plants4030393 - 8 Jul 2015
Cited by 234 | Viewed by 18910
Abstract
Generation of reactive oxygen species (ROS) is one of the earliest responses of plant cells to various biotic and abiotic stresses. ROS are capable of inducing cellular damage by oxidation of proteins, inactivation of enzymes, alterations in the gene expression, and decomposition of [...] Read more.
Generation of reactive oxygen species (ROS) is one of the earliest responses of plant cells to various biotic and abiotic stresses. ROS are capable of inducing cellular damage by oxidation of proteins, inactivation of enzymes, alterations in the gene expression, and decomposition of biomembranes. On the other hand, they also have a signaling role and changes in production of ROS can act as signals that change the transcription of genes that favor the acclimation of plants to abiotic stresses. Among the ROS, it is believed that H2O2 causes the largest changes in the levels of gene expression in plants. A wide range of plant responses has been found to be triggered by H2O2 such as acclimation to drought, photooxidative stress, and induction of senescence. Our knowledge on signaling roles of singlet oxygen (1O2) has been limited by its short lifetime, but recent experiments with a flu mutant demonstrated that singlet oxygen does not act primarily as a toxin but rather as a signal that activates several stress-response pathways. In this review we summarize the latest progress on the signaling roles of ROS during senescence and abiotic stresses and we give a short overview of the methods that can be used for their assessment. Full article
(This article belongs to the Special Issue Plant Senescence)
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620 KiB  
Review
Senescence Meets Dedifferentiation
by Yemima Givaty Rapp, Vanessa Ransbotyn and Gideon Grafi
Plants 2015, 4(3), 356-368; https://doi.org/10.3390/plants4030356 - 29 Jun 2015
Cited by 11 | Viewed by 13313
Abstract
Senescence represents the final stage of leaf development but is often induced prematurely following exposure to biotic and abiotic stresses. Leaf senescence is manifested by color change from green to yellow (due to chlorophyll degradation) or to red (due to de novo synthesis [...] Read more.
Senescence represents the final stage of leaf development but is often induced prematurely following exposure to biotic and abiotic stresses. Leaf senescence is manifested by color change from green to yellow (due to chlorophyll degradation) or to red (due to de novo synthesis of anthocyanins coupled with chlorophyll degradation) and frequently culminates in programmed death of leaves. However, the breakdown of chlorophyll and macromolecules such as proteins and RNAs that occurs during leaf senescence does not necessarily represent a one-way road to death but rather a reversible process whereby senescing leaves can, under certain conditions, re-green and regain their photosynthetic capacity. This phenomenon essentially distinguishes senescence from programmed cell death, leading researchers to hypothesize that changes occurring during senescence might represent a process of trans-differentiation, that is the conversion of one cell type to another. In this review, we highlight attributes common to senescence and dedifferentiation including chromatin structure and activation of transposable elements and provide further support to the notion that senescence is not merely a deterioration process leading to death but rather a unique developmental state resembling dedifferentiation. Full article
(This article belongs to the Special Issue Plant Senescence)
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