OsWRKY5 Promotes Rice Leaf Senescence via Senescence-Associated NAC and Abscisic Acid Biosynthesis Pathway.

he onset of leaf senescence is triggered by external cues and internal factors such as phytohormones and signaling pathways involving transcription factors (TFs). Abscisic acid (ABA) strongly induces senescence and endogenous ABA levels are finely tuned by many senescence-associated TFs. Here, we report on the regulatory function of the senescence-induced TF OsWRKY5 TF in rice ( ). expression was rapidly upregulated in senescing leaves, especially in yellowing sectors initiated by aging or dark treatment. A T-DNA insertion activation-tagged -overexpressing mutant (termed ) promoted leaf senescence under natural and dark-induced senescence (DIS) conditions. By contrast, a T-DNA insertion -knockdown mutant (termed ) retained leaf greenness during DIS. Reverse-transcription quantitative PCR (RT-qPCR) showed that upregulates the expression of genes controlling chlorophyll degradation and leaf senescence. Furthermore, RT-qPCR and yeast one-hybrid analysis demonstrated that OsWRKY5 indirectly upregulates the expression of senescence-associated () genes including and . Precocious leaf yellowing in the mutant might be caused by elevated endogenous ABA concentrations resulting from upregulated expression of ABA biosynthesis genes , , and , indicating that OsWRKY is a positive regulator of ABA biosynthesis during leaf senescence. Furthermore, expression was suppressed by ABA treatment. Taken together, is a positive regulator of leaf senescence that upregulates senescence-induced , ABA biosynthesis, and chlorophyll degradation genes.