Overexpression of ZmSAG39 in maize accelerates leaf senescence in Arabidopsis thaliana

Maize (Zea mays L.) is an annual gramineous herb and the second-largest food crop globally. Maize leaf senescence can restrict its yields. PLCP, a subfamily of cysteine proteases, plays a significant role in leaf senescence. However, the underlying regulatory mechanisms of maize leaf senescence remain unclear. In this study, the ZmSAG39 gene with significantly different expression levels was screened using the transcriptome sequencing analysis of maize cultivar H8186 in the laboratory in the early stage and the PLCP subfamily gene ZmSAG39 was cloned. The transgenic plants were treated with dark, drought and MeJA, and the relevant indexes were measured. In addition, the accumulation of reactive oxygen species (ROS) and the expression of related genes were analyzed. The expression of ZmSAG39 was up-regulated with the progression of leaf senescence in response to dark, drought, and MeJA treatments in maize. Ectopic overexpression of ZmSAG39 in Arabidopsis thaliana accelerated maize leaf senescence by up-regulating the expression of several leaf senescence-regulating genes and down-regulating photosynthesis-related genes. The senescence process of detached leaves of overexpressed lines was accelerated under MeJA and dark treatment, while drought treatment inhibited the germination rate of overexpressed lines and promoted ROS accumulation. In this study, we analyzed the function of the ZmSAG39 gene in maize leaf senescence, laying a foundation for further elucidating the molecular mechanism of maize leaf senescence and providing potential application value for maize breeding.