The VvBZR1-VvHY5 Module Integrates Brassinosteroid and Light Signaling to Regulate Anthocyanin Biosynthesis in Grape

Area of Science:

• Plant Biology
• Molecular Biology
• Biochemistry

Background:

• Brassinosteroid (BR) and light are known to promote anthocyanin synthesis in grape berries.
• The precise molecular mechanisms driving the synergistic interaction between BR and light signaling in this process are not fully understood.

Purpose of the Study:

• To elucidate the synergistic relationship between brassinosteroid (BR) and light signaling pathways in promoting anthocyanin accumulation in grape berries.
• To identify key regulatory components integrating these two signaling pathways.

Main Methods:

• Physiological and molecular analyses of gene expression.
• Overexpression studies in grape calli and Arabidopsis.
• Analysis of gene promoter activity using dual-luciferase assays.
• Protein-protein interaction studies including Yeast two-hybrid (Y2H), bimolecular fluorescence complementation (BiFC), and co-immunoprecipitation (Co-IP).

Main Results:

• VvBZR1 and VvHY5 were identified as key components mediating the synergistic effect.
• These proteins activate crucial anthocyanin biosynthesis genes (VvCHS1 and VvUFGT).
• Overexpression of VvBZR1 or VvHY5 increased anthocyanin content, with synergistic enhancement under combined light and 24-Epibrassinolide (EBR) treatment.
• VvBZR1 binds to the E-box in the VvUFGT promoter, and VvHY5 binds to the G-box in the VvCHS1 promoter.
• VvBZR1 and VvHY5 physically interact in vivo and in vitro, and this interaction enhances their transcriptional activation capabilities.

Conclusions:

• The VvBZR1-VvHY5 module acts as a critical positive regulator integrating BR and light signaling pathways.
• This regulatory module promotes anthocyanin synthesis in grape berries through direct transcriptional activation of key biosynthetic genes.
• The findings provide novel insights into the molecular mechanisms governing grape berry coloration.