Functional characterisation of five SVP genes in grape bud dormancy and flowering

The SHORT VEGETATIVE PHASE (SVP) gene is a member of the MADS-box family that has a pivotal role in regulating bud dormancy and flowering of perennials. The SVP genes have been widely investigated in numerous species. However, SVP gene functions in grape have not yet been characterised. In this study, five SVP genes were designated as VvSVP1, VvSVP2, VvSVP3, VvSVP4, VvSVP5. Phylogenetic analysis has shown that VvSVP genes are distributed into three different sub-clades. Gene expression analysis presented that SVP genes exhibit distinctive and temporal features, highly expressed in vegetative tissues and dormant buds. Moreover, the expression level was higher during para-dormancy and endo-dormancy stages, while lower expression was observed before bud-break, proposing VvSVP genes might be involved in bud dormancy regulation. Overexpression of VvSVP genes in Arabidopsis resulted in abnormal flower morphology and varying degrees of delayed flowering, but only VvSVP1, VvSVP2 and VvSVP4 recovered the early-flowering phenotype of Arabidopsis svp41 mutants. Additionally, ectopic overexpression of VvSVP1, VvSVP2 and VvSVP4 genes inhibited the expression of FLOWERING LOCUS T (AtFT) and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (AtSOC1) genes in both wild type Arabidopsis and its svp41 mutants. The results concluded that VvSVP1, VvSVP2 and VvSVP4 genes might serve as potential candidate genes in bud dormancy regulation and hindered flowering in grapes.