Li Shou, Gao Jiong, Yao Lingya, Ren Guodong, Zhu Xiaoyu, Gao Shan, Qiu Kai, Zhou Xin, Kuai Benke
State Key Laboratory of Genetic Engineering, Institute of Plant Biology, School of Life Sciences, Fudan University, 220 Handan Road, Shanghai, 200433, China.
Plant Cell Rep. 2016 Aug;35(8):1729-41. doi: 10.1007/s00299-016-1991-1. Epub 2016 May 6.
ANAC072 positively regulates both age- and dark-induced leaf senescence through activating the transcription of NYE1. Leaf senescence is integral to plant development, which is age-dependent and strictly regulated by internal and environmental signals. Although a number of senescence-related mutants and senescence-associated genes (SAGs) have been identified and characterized in the past decades, the general regulatory network of leaf senescence is still far from being elucidated. Here, we report the role of ANAC072, an SAG identified through bioinformatics analysis, in the regulation of chlorophyll degradation during natural and dark-induced leaf senescence. The expression of ANAC072 was increased with advancing leaf senescence in Arabidopsis. Leaf degreening was significantly delayed under normal or dark-induced conditions in anac072-1, a knockout mutant of ANAC072, with a higher chlorophyll level detected. In contrast, an overexpression mutant, anac072-2, with ANAC072 transcription markedly upregulated, showed an early leaf-yellowing phenotype. Consistently, senescent leaves of the loss-of-function mutant anac072-1 exhibited delays in the decrease of photosynthesis efficiency of photosystem II (F v/F m ratio) and the increase of plasma membrane ion leakage rate as compared with corresponding leaves of wild-type Col-0 plants, whereas the overexpression mutant anac072-2 showed opposite changes. Our data suggest that ANAC072 plays a positive role during natural and dark-induced leaf senescence. In addition, the transcript level of NYE1, a key regulatory gene in chlorophyll degradation, relied on the function of ANAC072. Combining these analyses with electrophoretic mobility shift assay and chromatin immunoprecipitation, we demonstrated that ANAC072 directly bound to the NYE1 promoter in vitro and in vivo, so ANAC072 may promote chlorophyll degradation by directly upregulating the expression of NYE1.
ANAC072通过激活NYE1的转录正向调控衰老和黑暗诱导的叶片衰老。叶片衰老对于植物发育不可或缺，它受年龄影响，并受到内部和环境信号的严格调控。尽管在过去几十年中已经鉴定并表征了许多衰老相关突变体和衰老相关基因（SAG），但叶片衰老的总体调控网络仍远未阐明。在此，我们报道了通过生物信息学分析鉴定的SAG——ANAC072在自然和黑暗诱导的叶片衰老过程中对叶绿素降解的调控作用。在拟南芥中，ANAC072的表达随着叶片衰老的推进而增加。在正常或黑暗诱导条件下，ANAC072的敲除突变体anac072 - 1的叶片褪绿显著延迟，检测到的叶绿素水平更高。相反，ANAC072转录明显上调的过表达突变体anac072 - 2表现出早期叶片黄化表型。一致地，与野生型Col - 0植物的相应叶片相比，功能缺失突变体anac072 - 1的衰老叶片在光系统II的光合效率降低（F v/F m比值）和质膜离子渗漏率增加方面表现出延迟，而过表达突变体anac072 - 2则表现出相反的变化。我们的数据表明，ANAC072在自然和黑暗诱导的叶片衰老过程中起积极作用。此外，叶绿素降解的关键调控基因NYE1的转录水平依赖于ANAC072的功能。结合这些分析以及电泳迁移率变动分析和染色质免疫沉淀，我们证明ANAC072在体外和体内直接与NYE1启动子结合，因此ANAC072可能通过直接上调NYE1的表达来促进叶绿素降解。
