Genome-wide identification of BAM genes in grapevine (Vitis vinifera L.) and ectopic expression of VvBAM1 modulating soluble sugar levels to improve low-temperature tolerance in tomato.

ABSTRACT

BACKGROUND: Low temperature (LT) is one of the main limiting factors that affect growth and development in grape. Increasing soluble sugar and scavenging reactive oxygen species (ROS) play critical roles in grapevine resistance to cold stress. However, the mechanism of ß-amylase (BAM) involved in the regulation of sugar levels and antioxidant enzyme activities in response to cold stress is unclear. RESULTS: In this study, six BAM genes were identified and clustered into four groups. Multiple sequence alignment and gene structure analysis showed that VvBAM6 lacked the Glu380 residue and contained only an exon. The transcript abundance of VvBAM1 and VvBAM3 significantly increased as temperature decreased. After LT stress, VvBAM1 was highly expressed in the leaves, petioles, stems, and roots of overexpressing tomato lines. The total amylase and BAM activities increased by 6.5- and 6.01-fold in transgenic plants compared with those in wild-type tomato plants (WT) subjected to LT, respectively. The glucose and sucrose contents in transgenic plants were significantly higher than those in WT plants, whereas the starch contents in the former decreased by 1.5-fold compared with those in the latter under LT stress. The analysis of transcriptome sequencing data revealed that 541 genes were upregulated, and 663 genes were downregulated in transgenic plants. One sugar transporter protein gene (SlSTP10), two peroxidase (POD)-related genes (SlPER7 and SlPER5), and one catalase (CAT)-related gene (SlCAT1) were upregulated by 8.6-, 3.6-, 3.0-, and 2.3-fold in transgenic plants after LT stress, respectively. CONCLUSIONS: Our results suggest that VvBAM1 overexpression promotes ROS scavenging and improves cold tolerance ability by modulating starch hydrolysis to affect soluble sugar levels in tomato plants.