Cloning, characterization and expression analysis of a brassinosteroids biosynthetic gene VvDET2 in Cabernet Sauvignon ( Vitis vinifera L.)

Brassinosteroids (BRs) play a crucial role in plant growth, development, and adaptation to environmental stress. DEETIOLATED2 (DET2) encodes 5α-reductases which catalyzes a rate-limiting step during the biosynthesis of BRs in plants. However, bioinformatic analysis and quantification of DET2 in grapes are rarely reported. Here, VvDET2 from the leaves of Cabernet Sauvignon ( Vitis vinifera L.) was isolated and characterized. The open reading frame of VvDET2 was 774 bp, encoding a peptide of 257 amino acids. The VvDET2 -predicted protein has a theoretical molecular mass of 29.69 kDa and an isoelectric point (pI) of 9.49. The phylogenetic analysis revealed that VvDET2 had a close evolutionary relationship with EpDET2 in Echinacea purpurea . The transcription of VvDET2 was detected in roots, leaves, stems, tendrils, and grape berries, as well as the occurrence of endogenous BRs. In fruit, the expression of VvDET2 decreased in both skins and seeds from E-L 31 to E-L 38 stage, while the content of total BRs peaked at E-L 36 stage. In addition, water stress substantially down-regulated the expression of VvDET2 and the content of total BRs in the leaves of grapevines. These results demonstrate that the regulation of grape berries ripeness and water stress response in Cabernet Sauvignon was closely associated with transcript levels of the VvDET2 and the content of total BRs.