RNA-Seq Based Transcriptomic Analysis of Bud Sport Skin Color in Grape Berries

The most common bud sport trait in grapevines is the change in color of grape berry skin, and the color of grapes is mainly developed by the composition and accumulation of anthocyanins. Many studies have shown that MYBA is a key gene regulates the initiation of bud sport color and anthocyanin synthesis in grape peels. In the current study, we used berry skins of 'Italia', 'Benitaka', 'Muscat of Alexandria', 'Flame Muscat', 'Rosario Bianco', 'Rosario Rosso', and 'Red Rosario' at the veraison stage (10 weeks post-flowering and 11 weeks post-flowering) as research materials. The relative expressions of genes related to grape berry bud sport skin color were evaluated utilizing RNA-Seq technology. The results revealed that the expressions of the VvMYBA1/A2 gene in the three red grape varieties at the veraison stage were higher than in the three white grape varieties. The VvMYBA1/A2 gene is known to be associated with UFGT in the anthocyanin synthesis pathway. According to the results, VvMYBA1/A2 gene expression could also be associated with the expression of LDOX. In addition, a single gene (gene ID: Vitvi19g01871) displayed the highest expressions in all the samples at the veraison stage for the six varieties. The expression of this gene was much higher in the three green varieties compared to the three red ones. GO molecular function annotation identified it as a putative metallothionein-like protein with the ability to regulate the binding of copper ions to zinc ions and the role of maintaining the internal stable state of copper ions at the cellular level. High expression levels of this screened gene may play an important role in bud sport color of grape berry skin at the veraison stage.

Automated summary

The most common bud sport trait in grapevines is the change in color of grape berry skin, which is mainly regulated by the MYBA gene and the synthesis of anthocyanins. In this study, the expressions of genes related to grape berry bud sport skin color were evaluated using RNA-Seq technology, and it was found that the VvMYBA1/A2 gene was highly expressed in red grape varieties compared to white grape varieties at the veraison stage. Additionally, a specific gene (gene ID: Vitvi19g01871) showed the highest expressions in all samples, and its high expression level may play an important role in the bud sport color of grape berry skin at the veraison stage.