The overexpression of SlBRI1 driven by Atrd29A promoter-transgenic plants improves the chilling stress tolerance of tomato

Main conclusion Overexpression of SlBRI1 driven by the Atrd29A promoter could increase the cold resistance of tomato plants during chilling stress but did not improve the expression of SlBRI1 and plant growth under normal conditions . Abstract Low temperature is the main limiting factor severely affecting tomato plant development, growth, and fruit quality in winter and spring. Brassinosteroids (BRs) and key BR signaling genes positively regulate tomato plant development and response to chilling stress. Brassinosteroid-insensitive 1 (BRI1) is a major BR receptor that initiates BR signaling. Our results showed that overexpression of SlBRI1 driven by the Atrd29A promoter in transgenic plants did not increase the expression of SlBRI1 under normal conditions but rapidly induced the expression of SlBRI1 during chilling stress. The degree of wilting was lower in Atrd29A promoter-transgenic plants than in wild-type (WT) plants after chilling stress. Atrd29A promoter-transgenic plants exhibited low relative electrolyte leakage and reactive oxygen species (ROS) accumulation under chilling stress. Transgenic plants showed higher photosynthetic ability and antioxidant enzyme activity than WT plants under chilling stress. The BR content and expression levels of key genes involved in BR biosynthesis in Atrd29A-promoter transgenic plants were significantly lower than those in WT plants during chilling stress. The abscisic acid (ABA) content and expression levels of key ABA biosynthesis genes in the Atrd29A promoter-transgenic plants were significantly higher than those in the WT plants during chilling stress. In addition, Atrd29A promoter-transgenic plants positively enhanced the expression levels of ICE–CBF–COR cold-responsive pathway genes. Therefore, the overexpression of SlBRI1 driven by the Atrd29A promoter in transgenic plants can be a valuable tool for reducing chilling stress.