PHYTOCHROME-INTERACTING FACTOR 5 (PIF5) positively regulates dark-induced senescence and chlorophyll degradation in Arabidopsis

• Published in: Plant science (Limerick) Vol. 237; pp. 57 - 68
• Main Authors: Zhang, Yongqiang, Liu, Zhongjuan, Chen, Yadi, He, Jun-Xian, Bi, Yurong
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier Ireland Ltd 01.08.2015
• Subjects: Arabidopsis - genetics; Arabidopsis - physiology; Arabidopsis - radiation effects; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Arabidopsis thaliana; Basic Helix-Loop-Helix Transcription Factors - genetics; Basic Helix-Loop-Helix Transcription Factors - metabolism; Cellular Senescence; Chlorophyll - metabolism; Chlorophyll degradation; Dark-induced senescence; Darkness; Gene Expression Regulation, Plant; Phytochrome - metabolism; PHYTOCHROME-INTERACTING FACTOR 5; Plant Leaves - genetics; Plant Leaves - physiology; Plant Leaves - radiation effects; Seedlings - genetics; Seedlings - physiology; Seedlings - radiation effects; Chlorophyll degradation; qRT-PCR; Dark-induced senescence; NOL; ORE1; TBARS; ChIP; PIF; PHYTOCHROME-INTERACTING FACTOR 5; REN LUC; Arabidopsis thaliana; CV; EMSA; SAG; fLUC; NYC1; CLH; PAO; SGR
• ISSN: 0168-9452; 1873-2259
• DOI: 10.1016/j.plantsci.2015.05.010

•Dark-induced senescence and chlorophyll degradation require PIF4 and PIF5.•Dark up-regulation of chlorophyll degradation-related genes requires PIF4 and PIF5.•PIF5 could bind to the promoters of SGR and NYC1.•PIF5 is an important upstream factor for dark-induced ORE1 expression. Darkness is a known environmental factor that induces plant senescence. Here, PHYTOCHROME-INTERACTING FACTORS (PIFs), several bHLH transcription factors involved in plant skotomorphogenesis, were examined for their roles in the regulation of dark-induced senescence and chlorophyll breakdown in Arabidopsis thaliana. After light-grown seedlings were transferred to darkness, green leaves turned yellow, and chlorophyll contents decreased, but membrane lipid peroxidation and cell death increased in wild-type Col-0. These responses were enhanced in overexpression line PIF5OX but decreased in mutant pif5-3. Darkness significantly induced expression of several genes involved in chlorophyll breakdown, including SGR, NYC1, NOL, and PAO, as well as genes encoding for transcription factors that have been shown to be required for dark-induced senescence, including WRKY22, NAP, EIN3, EIL1, and ORE1. These effects on gene expression were also enhanced in PIF5OX but decreased in pif5-3 relative to Col-0. Further analyses using ChIP-qPCR, EMSA, and protoplast transient assays indicated that PIF5 binds to the G-box motifs in the promoters of SGR, NYC1, and ORE1 genes and stimulate their expression. Collectively, our data indicate that PIF5 is a key factor that positively regulates dark-induced senescence upstream of ORE1 and regulates chlorophyll breakdown upstream of SGR and NYC1.