Zhang Yongqiang, Liu Zhongjuan, Chen Yadi, He Jun-Xian, Bi Yurong
Key Laboratory of Cell Activities and Stress Adaptations, Ministry of Education, School of Life Sciences, Lanzhou University, Lanzhou, Gansu 730000, People's Republic of China; School of Life Sciences and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong Special Administrative Region, China.
State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, Gansu 730000, People's Republic of China.
Plant Sci. 2015 Aug;237:57-68. doi: 10.1016/j.plantsci.2015.05.010. Epub 2015 May 19.
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.
黑暗是一种已知的诱导植物衰老的环境因素。在此，研究了植物光敏色素互作因子（PIFs），即几种参与植物暗形态建成的bHLH转录因子，在拟南芥黑暗诱导衰老和叶绿素降解调控中的作用。光照生长的幼苗转移到黑暗中后，野生型Col-0的绿叶变黄，叶绿素含量降低，但膜脂过氧化和细胞死亡增加。这些反应在过表达系PIF5OX中增强，而在突变体pif5-3中减弱。黑暗显著诱导了几个参与叶绿素降解的基因的表达，包括SGR、NYC1、NOL和PAO，以及编码已被证明是黑暗诱导衰老所必需的转录因子的基因，包括WRKY22、NAP、EIN3、EIL1和ORE1。相对于Col-0，这些对基因表达的影响在PIF5OX中也增强，而在pif5-3中减弱。使用ChIP-qPCR、EMSA和原生质体瞬时分析的进一步分析表明，PIF5与SGR、NYC1和ORE1基因启动子中的G-box基序结合并刺激它们的表达。总体而言，我们的数据表明，PIF5是在ORE1上游正向调节黑暗诱导衰老并在SGR和NYC1上游调节叶绿素降解的关键因子。
