Transcriptomic analysis reveals GA3 is involved in regulating flavonoid metabolism in grape development for facility cultivation.

Abstract

Gibberellin, as one of the pivotal plant growth regulators, can improve fruit quality by altering fruit size and secondary metabolite content. Flavonoids are the most abundant secondary metabolites in grapes, which influence the color and quality of the fruit. However, the molecular mechanism of whether and how GA3 affects flavonoid metabolism has not been reported, especially for the 'Red globe' grape with delayed cultivation in Hexi corridor. In the present study, the 'Red globe' grape grown in delayed facilities was sprayed with 20, 40, 60, 80 and 100mg/L GA3 at berries pea size (BPS), veraison (V) and berries ripe (BR), respectively. The results showed that the berry weight, soluble sugar content and secondary metabolite content (the flavonoid content, anthocyanin content and polyphenol content) at BR under 80mg/L GA3 treatment were remarkably increased compared with other concentration treatments. Therefore, RNA sequencing (RNA-seq) was used to analyze the differentially expressed genes (DEGS) and pathways under 80mg/L GA3 treatment at three periods. GO analysis showed that DEGs were closely related to transporter activity, cofactor binding, photosynthetic membrane, thylakoid, ribosome biogenesis and other items. The KEGG enrichment analysis found that the DEGs were mainly involved in flavonoid biosynthesis and phenylpropanoid biosynthesis, indicating GA3 exerted an impact on the color and quality of berries through these pathways. In conclusion, GA3 significantly increased the expression of genes related to flavonoid synthesis, enhanced the production of secondary metabolites, and improved fruit quality. In addition, these findings can provide a theoretical basis for GA3 to modulate the accumulation and metabolism of flavonoids in grape fruit.