scholarly journals The NAC transcription factor ANAC046 is a positive regulator of chlorophyll degradation and senescence in Arabidopsis leaves

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Chihiro Oda-Yamamizo ◽  
Nobutaka Mitsuda ◽  
Shingo Sakamoto ◽  
Daisuke Ogawa ◽  
Masaru Ohme-Takagi ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Transgenic Plants ◽  
Leaf Senescence ◽  
Loss Of Function ◽  
Pheophorbide A ◽  
Delayed Senescence ◽  
Positive Regulator ◽  
Catabolic Genes ◽  
Senescence Associated Genes ◽  
Senescence Phenotype

Abstract Chlorophyll (Chl) degradation occurs during leaf senescence, embryo degreening, bud breaking, and fruit ripening. The Chl catabolic pathway has been intensively studied and nearly all the enzymes involved are identified and characterized; however, the molecular regulatory mechanisms of this pathway are largely unknown. In this study, we performed yeast one-hybrid screening using a transcription factor cDNA library to search for factors controlling the expression of Chl catabolic genes. We identified ANAC046 as a common regulator that directly binds to the promoter regions of NON-YELLOW COLORING1, STAY-GREEN1 (SGR1), SGR2, and PHEOPHORBIDE a OXYGENASE. Transgenic plants overexpressing ANAC046 exhibited an early-senescence phenotype and a lower Chl content in comparison with the wild-type plants, whereas loss-of-function mutants exhibited a delayed-senescence phenotype and a higher Chl content. Microarray analysis of ANAC046 transgenic plants showed that not only Chl catabolic genes but also senescence-associated genes were positively regulated by ANAC046. We conclude that ANAC046 is a positive regulator of Arabidopsis leaf senescence and exerts its effect by controlling the expression of Chl catabolic genes and senescence-associated genes.

scholarly journals Ring/U-Box Protein AtUSR1 Functions in Promoting Leaf Senescence Through JA Signaling Pathway in Arabidopsis

2020 ◽  
Vol 11 ◽  
Author(s):  
Zenglin Zhang ◽  
Mengmeng Xu ◽  
Yongfeng Guo
Keyword(s):  
Transcription Factor ◽  
Signaling Pathway ◽  
Leaf Senescence ◽  
Luciferase Assay ◽  
Significant Delay ◽  
Delayed Senescence ◽  
Age Dependent ◽  
Ja Signaling ◽  
Senescence Phenotype

Leaf senescence is regulated by a large number of internal and environmental factors. Here, we report that AtUSR1 (U-box Senescence Related 1) which encodes a plant Ring/U-box protein, is involved in age-dependent and dark-induced leaf senescence in Arabidopsis. Expression of AtUSR1 gene in leaves was up-regulated in darkness and during aging. Plants of usr1, an AtUSR1 gene knock-down mutant, showed a significant delay in age-dependent and dark-induced leaf senescence and the delayed senescence phenotype was rescued when the AtUSR1 gene was transferred back to the mutant plants. Meanwhile, overexpression of AtUSR1 caused accelerated leaf senescence. Furthermore, the role of AtUSR1 in regulating leaf senescence is related to MYC2-mediuated jasmonic acid (JA) signaling pathway. MeJA treatments promoted the accumulation of AtUSR1 transcripts and this expression activation was dependent on the function of MYC2, a key transcription factor in JA signaling. Dual-luciferase assay results indicated that MYC2 promoted the expression of AtUSR1. Overexpression of AtUSR1 in myc2 mutant plants showed precocious senescence, while myc2 mutation alone caused a delay in leaf senescence, suggesting that AtUSR1 functions downstream to MYC2 in the JA signaling pathway in promoting leaf senescence.

scholarly journals Drought-induced Leaf Senescence and Horticultural Performance of Transgenic PSAG12-IPT Petunias

2004 ◽  
Vol 129 (1) ◽  
pp. 93-99 ◽  
Author(s):  
David G. Clark ◽  
Chris Dervinis ◽  
James E. Barrett ◽  
Harry Klee ◽  
Michelle Jones
Keyword(s):  
Transgenic Plants ◽  
Leaf Senescence ◽  
Plant Morphology ◽  
Fold Increase ◽  
Transcript Abundance ◽  
Plant Production ◽  
Mrna Levels ◽  
Delayed Senescence ◽  
Transgenic Lines ◽  
Senescence Phenotype

Cytokinins have been shown to delay the onset of leaf senescence. The focus of this project was to produce transgenic petunia (Petunia ×hybrida) plants that over-produced endogenous cytokinins in a senescence specific manner. This was achieved by transforming plants with the IPT (isopentenyl transferase) gene driven by the senescence-associated transcriptional promoter, PSAG12. Two independent transgenic events produced T1 and T2 generation seedling lines that demonstrated the desired nonsenescent phenotype in progeny trials. These lines were used to evaluate the horticultural performance of PSAG12-IPT petunia plants in terms of delayed senescence, rooting of vegetative cuttings, lateral branch growth, flower number, floral timing, and fruit set. Although both lines displayed a delayed senescence phenotype the two PSAG12-IPT transgenic lines differed from each other in regard to other horticultural traits. In addition to delayed leaf senescence, line I-1-7 also demonstrated a decrease in adventitious rooting and an increased number of branches during plant production. Line I-3-18 also demonstrated a delayed leaf senescence phenotype; however, plants of this line were not greatly altered in any other horticultural performance traits in comparison to wild-type `V26'. IPT transcript was detected in young fully expanded leaves of both lines, although mRNA levels were higher in I-1-7 plants. A greater than 50-fold increase in IPT transcript abundance was detected in leaves of transgenic plants following drought stress. These results demonstrate that it is possible to use PSAG12-IPT to produce transgenic plants with delayed leaf senescence but differences in plant morphology between transgenic lines exist, which may alter horticultural performance characteristics.

scholarly journals The leaf senescence-promoting transcription factor AtNAP activates its direct target gene CYTOKININ OXIDASE 3 to facilitate senescence processes by degrading cytokinins

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Youzhen Hu ◽  
Bin Liu ◽  
Huazhong Ren ◽  
Liping Chen ◽  
Christopher B. Watkins ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Leaf Senescence ◽  
Plant Hormones ◽  
Cytokinin Oxidase ◽  
In Planta ◽  
Delayed Senescence ◽  
Lateral Bud ◽  
Direct Target Gene ◽  
Fountain Of Youth ◽  
Senescence Phenotype

AbstractCytokinins (CKs) are a class of adenine-derived plant hormones that plays pervasive roles in plant growth and development including cell division, morphogenesis, lateral bud outgrowth, leaf expansion and senescence. CKs as a “fountain of youth” prolongs leaf longevity by inhibiting leaf senescence, and therefore must be catabolized for senescence to occur. AtNAP, a senescence-specific transcription factor has a key role in promoting leaf senescence. The role of AtNAP in regulating CK catabolism is unknown. Here we report the identification and characterization of AtNAP-AtCKX3 (cytokinin oxidase 3) module by which CKs are catabolized during leaf senescence in Arabidopsis. Like AtNAP, AtCKX3 is highly upregulated during leaf senescence. When AtNAP is chemically induced AtCKX3 is co-induced; and when AtNAP is knocked out, the expression of AtCKX3 is abolished. AtNAP physically binds to the cis element of the AtCKX3 promoter to direct its expression as revealed by yeast one-hybrid assays and in planta experiments. Leaves of the atckx3 knockout lines have higher CK concentrations and a delayed senescence phenotype compared with those of WT. In contrast, leaves with inducible expression of AtCKX3 have lower CK concentrations and exhibit a precocious senescence phenotype compared with WT. This research reveals that AtNAP transcription factor˗AtCKX3 module regulates leaf senescence by connecting two antagonist plant hormones abscisic acid and CKs.

scholarly journals Activation of the Transcription of BrGA20ox3 by a BrTCP21 Transcription Factor Is Associated with Gibberellin-Delayed Leaf Senescence in Chinese Flowering Cabbage during Storage

2019 ◽  
Vol 20 (16) ◽  
pp. 3860
Author(s):  
Xian-mei Xiao ◽  
Yan-mei Xu ◽  
Ze-xiang Zeng ◽  
Xiao-li Tan ◽  
Zong-li Liu ◽  
...  
Keyword(s):  
Transient Expression ◽  
Leaf Senescence ◽  
Biosynthetic Pathway ◽  
Transcript Level ◽  
Mobility Shift ◽  
Transient Expression Assay ◽  
Catabolic Genes ◽  
Mobility Shift Assay ◽  
Psii Quantum Yield ◽  
Senescence Associated Genes

Several lines of evidence have implicated the involvement of the phytohormone gibberellin (GA) in modulating leaf senescence in plants. However, upstream transcription factors (TFs) that regulate GA biosynthesis in association with GA-mediated leaf senescence remain elusive. In the current study, we report the possible involvement of a TEOSINTE BRANCHED1/CYCLOIDEA/PCF (TCP) TF BrTCP21 in GA-delayed leaf senescence in Chinese flowering cabbage. Exogenous GA3 treatment maintained a higher value of maximum PSII quantum yield (Fv/Fm) and total chlorophyll content, accompanied by the repression of the expression of senescence-associated genes and chlorophyll catabolic genes, which led to the delay of leaf senescence. A class I member of TCP TFs BrTCP21, was further isolated and characterized. The transcript level of BrTCP21 was low in senescing leaves, and decreased following leaf senescence, while GA3 could keep a higher expression level of BrTCP21. BrTCP21 was further found to be a nuclear protein and exhibit trans-activation ability through transient-expression analysis in tobacco leaves. Intriguingly, the electrophoretic mobility shift assay (EMSA) and transient expression assay illustrated that BrTCP21 bound to the promoter region of a GA biosynthetic gene BrGA20ox3, and activated its transcription. Collectively, these observations reveal that BrTCP21 is associated with GA-delayed leaf senescence, at least partly through the activation of the GA biosynthetic pathway. These findings expand our knowledge on the transcriptional mechanism of GA-mediated leaf senescence.

A novel BSD domain-containing transcription factor controls vegetative growth, leaf senescence, and fruit quality in tomato

2020 ◽  
Vol 71 (22) ◽  
pp. 6945-6957
Author(s):  
Youhong Fan ◽  
Xiangli Niu ◽  
Li Huang ◽  
Rachel Gross ◽  
Han Lu ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Leaf Senescence ◽  
Fruit Quality ◽  
Vegetative Growth ◽  
Soluble Solids ◽  
Loss Of Function ◽  
Physiological Processes ◽  
Associated Proteins ◽  
Leaf Tissues ◽  
Negative Role

Abstract BSD (mammalian BTF2-like transcription factors, synapse-associated proteins, and DOS2-like proteins) is a conserved domain that exists in a variety of organisms, but its function has not been well studied. Here, we identified a novel BSD domain-containing protein (SlBSD1) in tomato (Solanum lycopersicum). Biochemical and microscopy assays indicated that SlBSD1 is a functional transcription factor that is predominantly localized in the nucleus. Loss-of-function and overexpression analyses suggested that SlBSD1 is a novel regulator of vegetative growth and leaf senescence in tomato. SlBSD1-knockdown (-KD) plants exhibited retarded vegetative growth and precocious leaf senescence, whereas SlBSD1-overexpression (-OX) plants displayed the opposite phenotypes. The negative role of SlBSD1 in leaf senescence was also supported by RNA-seq analysis comparing leaf tissues from SlBSD1-KD and wild-type plants. In addition, contents of soluble solids were altered in fruits in the SlBSD1-KD and SlBSD1-OX plants. Taken together, our data suggest that the novel transcription factor SlBSD1 plays important roles in controlling fruit quality and other physiological processes in tomato, including vegetative growth and leaf senescence.

scholarly journals Regulation of Senescence by Sugar Metabolism

2003 ◽  
Author(s):  
David Granot ◽  
Richard Amasino
Keyword(s):  
Cell Death ◽  
Programmed Cell Death ◽  
Leaf Senescence ◽  
Sugar Metabolism ◽  
Regulatory Role ◽  
Tomato Plants ◽  
Hexokinase Activity ◽  
Delayed Senescence ◽  
Yeast Genes ◽  
Senescence Associated Genes

Research objectives a. Analyze transgenic plants that undergo rapid senescence due to increased expression of hexokinase. b. Determine if hexokinase-induced senescence accelerates natural senescence using senescence specific promoters that drive expression of a reporter gene (GUS) and a cytokinin producing gene (IPT - isopentyl transferase). c. Isolate and analyze plant genes that suppress sugar-induced cell death (SICD) in yeast, genes that potentially are involved in programmed cell death and senescence in plants. Background to the topic Leaf senescence is a regulated process of programmed cell death (PCD) in which metabolites are recycled to other active parts of the plant. Senescence associated genes (SAGs) are expressed throughout leaf senescence. Sugar flux and metabolism is thought to playa fundamental regulatory role in senescence. We found that transgenic tomato plants with high hexokinase activity, the initial enzymatic step of sugar (hexose) metabolism, undergo rapid leaf senescence, directly correlated with hexokinase activity. These plants provide a unique opportunity to analyze the regulatory role of sugar metabolism in senescence, and its relation to cytokinin, a senescence-inhibiting hormone. In addition, we found that sugar induces programmed cells death of yeast cells in direct correlation to hexokinase activity. We proposed to use the sugar induced cell death (SICD) to isolate Arabidopsis genes that suppress SICD. Such genes could potentially be involved in senescence induced PCD in plants. Major conclusions The promoters of Arabidopsis senescence-associated genes, SAG12 and SAGI3, are expressed in senescing tomato leaves similar to their expression in Arabidopsis leaves, indicating that these promoters are good senescence markers for tomato plants. Increased hexokinase activity accelerated senescence and induced expression of pSAG12 and pSAG13 promoters in tomato plants, suggesting that sugar regulate natural senescence via hexokinase. Expression of IPT, a cytokinin producing gene, under pSAG12 and pSAG13 promoters, delayed senescence of tomato leaves. Yet, senescence accelerated by hexokinase was epistatic over cytokinin, indicating that sugar regulation of senescence is dominant over the senescence-inhibiting hormone. A gene designated SFP1, which is similar to the major super family monosaccharide transporters, is induced during leaf senescence in Arabidopsis and may be involved in sugar transport during senescence. Accordingly, adult leaves accumulate sugars that may accelerate hexokinase activity. Light status of the entire plant affects the senescence of individual leaves. When individual leaves are darkened, senescence is induced in the covered leaves. However, whole adult plant placed in darkness show delayed senescence. In a search for Arabidopsis genes that suppress SICD we isolated 8 cDNA clones which confer partial resistance to SICD. One of the clones encodes a vesicle associated membrane protein - VAMP. This is the first evidence that vesicle trafficking might be involved in cell death. Implications Increased hexokinase activity accelerates senescence. We hypothesized that, reduced hexokinase activity may delay senescence. Preliminary experiments using a hexokinase inhibitor support this possible implication. Currently we are analyzing various practical approaches to delay leaf senescence via hexokinase inhibition. .

scholarly journals Transcription Factor NAC075 Delays Leaf Senescence by Deterring Reactive Oxygen Species Accumulation in Arabidopsis

2021 ◽  
Vol 12 ◽  
Author(s):  
Chengcheng Kan ◽  
Yi Zhang ◽  
Hou-Ling Wang ◽  
Yingbai Shen ◽  
Xinli Xia ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Transcription Factor ◽  
Leaf Senescence ◽  
Critical Role ◽  
Reactive Oxygen ◽  
Negative Regulator ◽  
Dependent Manner ◽  
Oxygen Species ◽  
Loss Of Function ◽  
Mobility Shift

Leaf senescence is a highly complex genetic process that is finely tuned by multiple layers of regulation. Among them, transcriptional regulation plays a critical role in controlling the initiation and progression of leaf senescence. Here, we found that the NAC transcription factor NAC075 functions as a novel negative regulator of leaf senescence. Loss of function of NAC075 promotes leaf senescence in an age-dependent manner, whereas constitutive overexpression of NAC075 delays senescence in Arabidopsis. Transcriptome analysis revealed that transcript levels of antioxidant enzymes such as catalase (CAT), ascorbate peroxidase (APX), and superoxide dismutase (SOD) are significantly suppressed in nac075 mutants compared with wild-type plants. Electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) analyses revealed that NAC075 directly binds the promoter of catalase 2 (CAT2). Moreover, genetic analysis showed that overexpression of CAT2 suppresses the overproduction of reactive oxygen species (ROS) and the early senescence phenotypes of nac075 mutants, suggesting that CAT2 acts downstream of NAC075 to delay leaf senescence by repressing ROS accumulation. Collectively, our findings provide a new regulatory module involving NAC075-CAT2-ROS in controlling leaf senescence in Arabidopsis.

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