The BES1/BZR1 transcriptional factor SlBES2 cross talks with abscisic acid to regulate fruit maturation in tomato

Abscisic acid plays a pivotal role in initiating fruit maturation, yet the underlying mechanism is still far from being clearly revealed. This study identified a tomato BES1/BZR1 transcriptional factor SlBES2 as a regulator of fruit maturation through comparative observation of SlBES2-overexpressing and SlBES2-repressing tomato lines. The peaks of fruit abscisic acid content were advanced in SlBES2-overexpressing lines but delayed in SlBES2-repressing lines. And the variations of fruit abscisic acid content were negatively correlated with the gene expression patterns of SlBES2 during fruit maturation. Comparative transcriptome and gene expression analysis revealed that SlBES2 regulates expression levels of genes involved in abscisic acid biosynthesis and catabolism pathway. In turn, both the gene expression level and unphosphorylated protein abundance of SlBES2 are negatively regulated by abscisic acid with the approach of fruit maturation. In addition, SlBES2 physically interacts with type 2C protein phosphatases and the interaction could be inhibited by abscisic acid, indicating that type 2C protein phosphatases might mediate the crosstalk between SlBES2 and abscisic acid signaling pathway. Together, this study demonstrates that SlBES2 cross talks with abscisic acid during fruit maturation, coordinatively regulating fruit maturation and synchronism of maturity. Our findings contribute a new actor to the complex mechanisms underlying fruit maturation and may provide insights for potential breeding strategies aimed at improving synchronism of fruit maturity.