SlGAD2is the target of SlTHM27, positively regulates cold tolerance by mediating anthocyanin biosynthesis in tomato

Cold stress significantly limits the yield and quality of tomato. Deciphering the key genes related to cold tolerance is important for selecting and breeding superior cold-tolerant varieties. γ-aminobutyric acid (GABA) responds to various types of stress by rapidly accumulating in plant. In this study, glutamic acid decarboxylase (GAD2) was a positive regulator to enhance cold stress tolerance of tomato. Overexpression of SlGAD2decreased the extent of cytoplasmic membrane damage and increased the endogenous GABA content, antioxidant enzyme activities, and reactive oxygen species (ROS) scavenging capacity in response to cold stress, whereas Slgad2mutant plants showed the opposite trend. In addition, SlGAD2induced anthocyanin biosynthesis in response to cold stress by increasing the content of endogenous GABA. Further study revealed that SlGAD2expression was negatively regulated by the transcription factor SlTHM27. However, the transcript levels of SlTHM27were repressed under cold stress. Antioxidant enzyme activities, SlGAD2transcript levels, GABA and anthocyanin contents were significantly increased in Slthm27mutant plants. Further, our study demonstrated that SlTHM27 decreases SlGAD2-promoted cold resistance in tomato by repressing SlGAD2transcription. Overall, our results showed that the SlTHM27-SlGAD2model regulates the cold tolerance in tomato by regulating GABA and anthocyanin.