RNA-sequencing analysis of candidate genes involved in berry development in 'Summer Black' grapes and its early bud mutants varieties

Berry development time and early maturity are important breeding traits in grapes. The mechanisms for early grape bud mutants remain unclear. Grape development is divided into three major phases known as the modified E–L system. This study measured fructose, glucose, tartaric acid, gallic acid, malic acid, and dihydroquercetin of ‘Summer Black’ and its bud mutants cultivars ‘Chunxiangwuhe,’ ‘Zaoxiaxiang,’ and ‘Sanbenti’ at different fruit development stages to determine their role in fruit maturity. RNA-sequencing analysis was used to identify the genes involved in fruit ripening. The results showed that fructose and glucose were accumulatedearlier during the EL-34 stage of the early bud mutants cultivars, whereas malic and tartaric acids levels showed a significant downward trend. Gene set enrichment analysis and weighted gene co-correlation network analysis showed that the differentially expressed genes were primarily enriched in flavonoid biosynthesis and galactose metabolism. Some candidate genes, including GAST1, APX2, ATHB-12, and AOS1, were identified via DEG and transcription factor prediction analyses. These genes play an essential role in the development of grape berries. The role of these genes was verified via qRT-PCR. The results of this study provide a theoretical basis for the genetic improvement of grapes.