VvBAP1 Is Involved in Cold Tolerance in Vitis vinifera L

The majority of commercial grape cultivars originate from the European grape. While these cultivars have excellent organoleptic qualities, they suffer from a relatively poor tolerance to the cold experienced during winter, resulting in significant damage to grapevines. Thus, low temperature is one of the bottlenecks that restrict the further growth of the grape industry. Research on the mechanism of cold tolerance in grapes is therefore very important. BON association protein 1 (BAP1) is a recently discovered phospholipid-binding protein. In Arabidopsis, the expression of AtBAP1 can be regulated via low temperature; however, the function of BAP1 in the grapevine has not been reported. The VvBAP1 gene was cloned in our previous studies in grapes, and bioinformatics analysis showed that it harbors the conservative calcium-dependent C2 protein domain. However, little is known about its function and underlying mechanism. In this study, cold treatment was applied to the cold-resistant grape varieties 'F-242' and 'Zuoyouhong' as well as to the cold-sensitive grape varieties 'Cabernet Sauvignon' and 'Chardonnay.' The expression level of VvBAP1 in the cold-resistant varieties was significantly higher than in the cold-sensitive varieties, indicating that VvBAP1 could be associated with the cold response processes in the grapevine. Using the cold-resistant grape variety 'F-242' as material, with the 4°C and CaCl₂ treatment, the relative expression of VvBAP1 was determined via qRT-PCR. Both low temperature and low-temperature signal Ca²⁺ induced VvBAP1 expression. In addition, the VvBAP1 gene was cloned and transferred into Arabidopsis to generate VvBAP1 overexpressing plants. Biochemical assays and gene expression analyses were conducted on plants subjected to low temperature treatments (4 and -8°C). The obtained results showed that the activities of superoxide dismutase and peroxidase in these transgenic plants were higher than those in wild type (WT) plants, and that cell membrane permeability and malondialdehyde content were both lower compared to WT plants. Furthermore, the content of soluble sugars and the expression levels of sugar-metabolizing related genes, such as BAM4-7, SS4, and G6PD5, were significantly higher than those of WT plants. Furthermore, the expression of low temperature response signal genes, including CBF1, CBF3, COR15a, COR6.6, COR27, and KIN1, were also enhanced. In summary, these results showed that VvBAP1 could strengthen the cold resistance in the grapevine through adjusting and controlling the sugar content and activating antioxidant enzyme activity.