Overexpression of VaSS4 negatively regulates cold tolerance by disturbing ROS balance and decreasing soluble sugar content

Abstract

Cold stress is one of the major limiting factors for grapevine growth and yield. Sucrose synthetase (SS) is a glycosyl transferase enzyme involved in plant sugar metabolism, which is essential for plant growth and development and response to abiotic stress. However, the function of SS genes in grape cold resistance has not been systematically understood. In the present study, a SS gene from Vitis amurensis named VaSS4 was identified, which was significantly suppressed in response to cold stress. The physicochemical properties, evolutionary relationships, synteny, and selection pressure of VaSS4 were analyzed. Furthermore, VaSS4-overexpressed Arabidopsis and grape calli were obtained to characterize their tolerance to cold stress. Amino acid sequence analysis demonstrated that VaSS4 protein encoded 806 amino acids and contained conserved sucrose synthase domain and glycosyl transferase domain. Overexpression of VaSS4 decreased SS decomposition activity and soluble sugar accumulation under cold stress. Meanwhile, VaSS4 overexpression decreased the reactive oxygen scavenging ability and cold tolerance of Arabidopsis and grape calli. Importantly, overexpression of VaSS4 negatively regulated the expression of cold-related genes in the CBF-dependent pathway compared with WT plants. Overall, these findings not only provide extensive systematic information for Vitis amurensis VaSS4 gene research, but also provide valuable germplasm resources for grape cold resistance breeding.