College of Agro-Grassland Science, Nanjing Agricultural University, Nanjing 210095, China.
Department of Plant Biology, Rutgers University, New Brunswick, New Jersey 08901, USA.
Plant Physiol. 2022 Jun 1;189(2):595-610. doi: 10.1093/plphys/kiac070.
Expression of chlorophyll (Chl) catabolic genes during leaf senescence is tightly controlled at the transcriptional level. Here, we identified a NAC family transcription factor, LpNAL, involved in regulating Chl catabolic genes via the yeast one-hybrid system based on truncated promoter analysis of STAYGREEN (LpSGR) in perennial ryegrass (Lolium perenne L.). LpNAL was found to be a transcriptional repressor, directly repressing LpSGR as well as the Chl b reductase gene, NONYELLOWING COLORING1. Perennial ryegrass plants over-expressing LpNAL exhibited delayed leaf senescence or stay-green phenotypes, whereas knocking down LpNAL using RNA interference accelerated leaf senescence. Comparative transcriptome analysis of leaves at 30 d after emergence in wild-type, LpNAL-overexpression, and knock-down transgenic plants revealed that LpNAL-regulated stay-green phenotypes possess altered light reactions of photosynthesis, antioxidant metabolism, ABA and ethylene synthesis and signaling, and Chl catabolism. Collectively, the transcriptional repressor LpNAL targets both Chl a and Chl b catabolic genes and acts as a brake to fine-tune the rate of Chl degradation during leaf senescence in perennial ryegrass.
叶绿素（Chl）分解代谢基因在叶片衰老过程中的表达受到转录水平的严格控制。在这里，我们通过基于多年生黑麦草（Lolium perenne L.）中 STAYGREEN（LpSGR）的截短启动子分析，利用酵母单杂交系统鉴定了一个参与调节 Chl 分解代谢基因的 NAC 家族转录因子 LpNAL。发现 LpNAL 是一个转录抑制子，直接抑制 LpSGR 以及叶绿素 b 还原酶基因 NONYELLOWING COLORING1。过表达 LpNAL 的多年生黑麦草植物表现出叶片衰老延迟或保持绿色的表型，而使用 RNA 干扰敲低 LpNAL 则加速了叶片衰老。在野生型、LpNAL 过表达和敲低转基因植物中，出芽后 30 天叶片的比较转录组分析表明，LpNAL 调节的保持绿色表型具有改变的光合作用光反应、抗氧化代谢、ABA 和乙烯合成和信号转导以及 Chl 分解代谢。总的来说，转录抑制因子 LpNAL 靶向 Chl a 和 Chl b 分解代谢基因，并作为制动器，在多年生黑麦草叶片衰老过程中精细调节 Chl 降解的速度。
