Flavonoids are critical secondary metabolites that determine the health benefits and flavor of tea,while chlorophylls are important contributors to the appearance of tea.However,transcription factors(TFs)that can inte...Flavonoids are critical secondary metabolites that determine the health benefits and flavor of tea,while chlorophylls are important contributors to the appearance of tea.However,transcription factors(TFs)that can integrate both chlorophyll biosynthesis and flavonoid accumulation in response to specific light signals are rarely identified.In this study,we report that the GOLDEN 2-LIKE TF pair,CsGLK1 and CsGLK2,orchestrate UV-B-induced responses in the chlorophyll biosynthesis and flavonoid accumulation of tea leaves.The absence of solar UV-B reduced the transcriptional expression of CsGLKs in the tea leaves and was highly correlated with a decrease in flavonoid levels(especially flavonol glycosides)and the expression of genes and TFs involved in chlorophyll biosynthesis and flavonoid accumulation.In vivo and in vitro molecular analyses showed that CsGLKs could be regulated by the UV-B signal mediator CsHY5,and could directly bind to the promoters of gene and TF involved in light-harvesting(CsLhcb),chlorophyll biosynthesis(CsCHLH,CsHEMA1,and CsPORA),and flavonoid accumulation(CsMYB12,CsFLSa,CsDFRa,and CsLARa),eventually leading to UV-B-induced responses in the chlorophylls and flavonoids of tea leaves.Furthermore,UV-B exposure increased the levels of total flavonoids,CsGLK1 protein,and expression of CsGLKs and target genes in the tea leaves.These results indicate that CsGLKs may modulate tea leaf characteristics by regulating chlorophyll biosynthesis and flavonoid accumulation in response to solar UV-B.As the first report on UV-B-induced changes in flavonoid and chlorophyll regulation mediated by CsGLKs,this study improves our understanding of the environmental regulations regarding tea quality and sheds new light on UV-B-induced flavonoid responses in higher plants.展开更多
The timing of flowering is tightly controlled by signals that integrate environmental and endogenous cues.Sugars produced by carbon fixation in the chloroplast are a crucial endogenous cue for floral initiation.Chloro...The timing of flowering is tightly controlled by signals that integrate environmental and endogenous cues.Sugars produced by carbon fixation in the chloroplast are a crucial endogenous cue for floral initiation.Chloroplasts also convey information directly to the nucleus through retrograde signaling to control plant growth and development.Here,we show that mutants defective in chlorophyll biosynthesis and chloroplast development flowered early,especially under long-day conditions,although low sugar accumulation was seen in some mutants.Plants treated with the bleaching herbicide norflurazon also flowered early,suggesting that chloroplasts have a role in floral repression.Among retrograde signaling mutants,the golden2-like 1(glk1)glk2 double mutants showed early flowering under long-day conditions.This early flowering was completely suppressed by constans(co)and flowering locus t(ft)mutations.Leaf vascular-specific knockdown of both GLK1 and GLK2 phenocopied the glk1 glk2 mutants.GLK1 and GLK2 repress flowering by directly activating the expression of B-BOX DOMAIN PROTEIN 14(BBX14),BBX15,and BBX16 via CCAATC cis-elements in the BBX genes.BBX14/15/16 physically interact with CO in the nucleus,and expression of BBXs hampered CO-mediated FT transcription.Simultaneous knockdown of BBX14/15/16 by artificial miRNA(35S::amiR-BBX14/15/16)caused early flowering with increased FT transcript levels,whereas BBX overexpression caused late flowering.Flowering of glk1/2 and 35S::amiR-BBX14/15/16 plants was insensitive to norflurazon treatment.Taking these observations together,we propose that the GLK1/2-BBX14/15/16 module provides a novel mechanism explaining how the chloroplast represses flowering to balance plant growth and reproductive development.展开更多
Leaf senescence can be triggered and promoted by a large number of developmental and environmental fac- tors. Numerous lines of evidence have suggested an involvement of phytochromes in the regulation of leaf senescen...Leaf senescence can be triggered and promoted by a large number of developmental and environmental fac- tors. Numerous lines of evidence have suggested an involvement of phytochromes in the regulation of leaf senescence, but the related signaling pathways and physiological mechanisms are poorly understood. In this study, we initially identi- fied phytochrome-interacting factors （PIFs） 3, 4, and 5 as putative mediators of leaf senescence. Mutations of the PIF genes resulted in a significantly enhanced leaf longevity in age-triggered and dark-induced senescence, whereas overexpressions of these genes accelerated age-triggered and dark-induced senescence in Arabidopsis. Consistently, loss-of-function of PIF4 attenuated dark-induced transcriptional changes associated with chloroplast deterioration and reactive oxygen species （ROS） generation. ChlP-PCR and DualoLuciferase assays demonstrated that PIF4 can activate chlorophyll degradation regulatory gene NYE1 and repress chloroplast activity maintainer gene GLK2 by binding to their promoter regions. Finally, dark-induced ethylene biosynthesis and ethylene-induced senescence were both dampened in pif4, suggesting the involvement of PIF4 in both ethylene biosynthesis and signaling pathway. Our study provides evidence that PIF3, 4, and 5 are novel positive senes- cence mediators and gains an insight into the mechanism of light signaling involved in the regulation of leaf senescence.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant Nos.32072623,31700611)。
文摘Flavonoids are critical secondary metabolites that determine the health benefits and flavor of tea,while chlorophylls are important contributors to the appearance of tea.However,transcription factors(TFs)that can integrate both chlorophyll biosynthesis and flavonoid accumulation in response to specific light signals are rarely identified.In this study,we report that the GOLDEN 2-LIKE TF pair,CsGLK1 and CsGLK2,orchestrate UV-B-induced responses in the chlorophyll biosynthesis and flavonoid accumulation of tea leaves.The absence of solar UV-B reduced the transcriptional expression of CsGLKs in the tea leaves and was highly correlated with a decrease in flavonoid levels(especially flavonol glycosides)and the expression of genes and TFs involved in chlorophyll biosynthesis and flavonoid accumulation.In vivo and in vitro molecular analyses showed that CsGLKs could be regulated by the UV-B signal mediator CsHY5,and could directly bind to the promoters of gene and TF involved in light-harvesting(CsLhcb),chlorophyll biosynthesis(CsCHLH,CsHEMA1,and CsPORA),and flavonoid accumulation(CsMYB12,CsFLSa,CsDFRa,and CsLARa),eventually leading to UV-B-induced responses in the chlorophylls and flavonoids of tea leaves.Furthermore,UV-B exposure increased the levels of total flavonoids,CsGLK1 protein,and expression of CsGLKs and target genes in the tea leaves.These results indicate that CsGLKs may modulate tea leaf characteristics by regulating chlorophyll biosynthesis and flavonoid accumulation in response to solar UV-B.As the first report on UV-B-induced changes in flavonoid and chlorophyll regulation mediated by CsGLKs,this study improves our understanding of the environmental regulations regarding tea quality and sheds new light on UV-B-induced flavonoid responses in higher plants.
基金supported by a National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(no.2022R1A3B1078180).
文摘The timing of flowering is tightly controlled by signals that integrate environmental and endogenous cues.Sugars produced by carbon fixation in the chloroplast are a crucial endogenous cue for floral initiation.Chloroplasts also convey information directly to the nucleus through retrograde signaling to control plant growth and development.Here,we show that mutants defective in chlorophyll biosynthesis and chloroplast development flowered early,especially under long-day conditions,although low sugar accumulation was seen in some mutants.Plants treated with the bleaching herbicide norflurazon also flowered early,suggesting that chloroplasts have a role in floral repression.Among retrograde signaling mutants,the golden2-like 1(glk1)glk2 double mutants showed early flowering under long-day conditions.This early flowering was completely suppressed by constans(co)and flowering locus t(ft)mutations.Leaf vascular-specific knockdown of both GLK1 and GLK2 phenocopied the glk1 glk2 mutants.GLK1 and GLK2 repress flowering by directly activating the expression of B-BOX DOMAIN PROTEIN 14(BBX14),BBX15,and BBX16 via CCAATC cis-elements in the BBX genes.BBX14/15/16 physically interact with CO in the nucleus,and expression of BBXs hampered CO-mediated FT transcription.Simultaneous knockdown of BBX14/15/16 by artificial miRNA(35S::amiR-BBX14/15/16)caused early flowering with increased FT transcript levels,whereas BBX overexpression caused late flowering.Flowering of glk1/2 and 35S::amiR-BBX14/15/16 plants was insensitive to norflurazon treatment.Taking these observations together,we propose that the GLK1/2-BBX14/15/16 module provides a novel mechanism explaining how the chloroplast represses flowering to balance plant growth and reproductive development.
文摘Leaf senescence can be triggered and promoted by a large number of developmental and environmental fac- tors. Numerous lines of evidence have suggested an involvement of phytochromes in the regulation of leaf senescence, but the related signaling pathways and physiological mechanisms are poorly understood. In this study, we initially identi- fied phytochrome-interacting factors （PIFs） 3, 4, and 5 as putative mediators of leaf senescence. Mutations of the PIF genes resulted in a significantly enhanced leaf longevity in age-triggered and dark-induced senescence, whereas overexpressions of these genes accelerated age-triggered and dark-induced senescence in Arabidopsis. Consistently, loss-of-function of PIF4 attenuated dark-induced transcriptional changes associated with chloroplast deterioration and reactive oxygen species （ROS） generation. ChlP-PCR and DualoLuciferase assays demonstrated that PIF4 can activate chlorophyll degradation regulatory gene NYE1 and repress chloroplast activity maintainer gene GLK2 by binding to their promoter regions. Finally, dark-induced ethylene biosynthesis and ethylene-induced senescence were both dampened in pif4, suggesting the involvement of PIF4 in both ethylene biosynthesis and signaling pathway. Our study provides evidence that PIF3, 4, and 5 are novel positive senes- cence mediators and gains an insight into the mechanism of light signaling involved in the regulation of leaf senescence.
