title: Age-triggered and dark-induced leaf senescence require the bHLH transcription factors PIF3, 4, and 5.
abstract: Leaf senescence can be triggered and promoted by a large number of developmental and environmental factors. 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 identified 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. ChIP-PCR and Dual-Luciferase 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 senescence mediators and gains an insight into the mechanism of light signaling involved in the regulation of leaf senescence.
authors.affiliation: State Key Laboratory of Genetic Engineering, Institute of Plant Biology, School of Life Sciences, Fudan University, Shanghai 200433, People's Republic of China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Song
authors.affiliation: State Key Laboratory of Genetic Engineering, Institute of Plant Biology, School of Life Sciences, Fudan University, Shanghai 200433, People's Republic of China.
authors.forename: Chuangwei
authors.initials: C
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Genetic Engineering, Institute of Plant Biology, School of Life Sciences, Fudan University, Shanghai 200433, People's Republic of China.
authors.forename: Shan
authors.initials: S
authors.lastname: Gao
authors.affiliation: National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Genetic Engineering, Institute of Plant Biology, School of Life Sciences, Fudan University, Shanghai 200433, People's Republic of China linli@fudan.edu.cn bkkuai@fudan.edu.cn.
authors.forename: Lin
authors.initials: L
authors.lastname: Li
authors.affiliation: State Key Laboratory of Genetic Engineering, Institute of Plant Biology, School of Life Sciences, Fudan University, Shanghai 200433, People's Republic of China linli@fudan.edu.cn bkkuai@fudan.edu.cn.
authors.forename: Benke
authors.initials: B
authors.lastname: Kuai
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000502:physiology*; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000502:physiology*; D002736:Chloroplasts / Q000502:physiology; D003624:Darkness; D018506:Gene Expression Regulation, Plant; D055786:Gene Knockout Techniques; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D010834:Phytochrome / Q000502:physiology*; D018515:Plant Leaves / Q000502:physiology*; D015398:Signal Transduction
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D010834:Phytochrome; C116162:PIF3 protein, Arabidopsis; C459466:PIF4 protein, Arabidopsis; C497729:PIF5 protein, Arabidopsis
keywords: GLK2; NYE1/SGR1; chloroplast deterioration; ethylene.; leaf senescence; phytochrome-interacting factor (PIF)