RNA-Seq of Arabidopsis thaliana

Leaf senescence is the final stage of leaf development, which is jointly affected by various exogenous and endogenous factors. Among them, salicylic acid (SA), jasmonic acid (JA), and transcription factors are the key regulatory factors of leaf senescence, whereas the molecular mechanisms remain largely unclear. In this study, we found that the leaf senescence of myb59 mutant plants was significantly earlier than that of wild-type plants, and the compensatory lines under the background of myb59-1 plants restored the leaf senescence to wild-type level, which proved that MYB59 was a negative regulator of age-dependent leaf senescence. Expression pattern analysis showed that MYB59 was dominantly expressed in the rosette leaves at early senescence stage. RNA sequencing revealed that a large number of senescence-related genes were differentially expressed between wild-type and myb59-1 plants. Chromatin immunoprecipitation assays and transient dual-luciferase reporter analysis demonstrated that MYB59 directly bound to SENESCENCE ASSOCIATED GENE 18 (SAG18) promoter and repressed its transcriptional activity. Moreover, MYB59 inhibited SA production by directly repressing ISOCHORISMATE SYNTHASE 1 (ICS1) and PHENYLALANINE AMMONIA-LYASE 2 (PAL2) expression and restrained JA biosynthesis by directly suppressing LIPOXYGENASE 2 (LOX2) expression. Application of exogenous SA, MeJA, and their inhibitors proved that MYB59 negatively regulated SA- and JA-mediated leaf senescence. These results help us to understand the novel function of MYB59 and provide new insights into the regulatory network of transcription factors controlling leaf senescence in Arabidopsis thaliana.