A Tripartite Amplification Loop Involving the Transcription Factor WRKY75, Salicylic Acid, and Reactive Oxygen Species Accelerates Leaf Senescence

Pengru Guo, Zhonghai Li, Peixin Huang, Bosheng Li, Shuang Fang, Jinfang Chu, Hongwei Guo
2017 The Plant Cell  
Leaf senescence is a highly coordinated, complicated process involving the integration of numerous internal and environmental signals. Salicylic acid (SA) and reactive oxygen species (ROS) are two well-defined inducers of leaf senescence whose contents progressively and interdependently increase during leaf senescence via an unknown mechanism. Here, we characterized the transcription factor WRKY75 as a positive regulator of leaf senescence in Arabidopsis thaliana. Knockdown or knockout of
more » ... delayed age-dependent leaf senescence, while overexpression of WRKY75 accelerated this process. WRKY75 transcription is induced by age, SA, H 2 O 2 , and multiple plant hormones. Meanwhile, WRKY75 promotes SA production by inducing the transcription of SA INDUCTION-DEFICIENT2 (SID2) and suppresses H 2 O 2 scavenging, partly by repressing the transcription of CATALASE2 (CAT2). Genetic analysis revealed that the mutation of SID2 or an increase in catalase activity rescued the precocious leaf senescence phenotype evoked by WRKY75 overexpression. Based on these results, we propose a tripartite amplification loop model in which WRKY75, SA, and ROS undergo a gradual but self-sustained rise driven by three interlinking positive feedback loops. This tripartite amplification loop provides a molecular framework connecting upstream signals, such as age and plant hormones, to the downstream regulatory network executed by SA-and H 2 O 2 -responsive transcription factors during leaf senescence.
doi:10.1105/tpc.17.00438 pmid:29061866 pmcid:PMC5728132 fatcat:z2tvmne3nfcstle4l5evfpw2u4