Comparative analysis of the gene expression profile under two cultivation methods reveals the critical role of ABA in grape quality promotion

Abstract

Root restriction is a critical cultivation technique that accelerates ripening and improves fruit quality, by a still unknown mechanism. ABA is an important phytohormone in both ripening and stress responses. To elucidate the relationship between ABA content and root restriction-induced fruit quality promotion, the endogenous ABA level was investigated in five-year-old ‘Muscat Hamburg’ grapevines from the pre-anthesis stage to maturity. The results showed that ABA production was significantly enhanced by root restriction. A transcriptomics-based approach was taken to identify transcriptionally regulated genes associated with ABA biosynthesis, catabolism and signal transduction in the four development periods of grape. A total of 2873 (884 upregulated and 1989 downregulated) DEGs were identified in all stages. Those related to metabolic processes, cellular processes, responses to stimuli, biological regulation and signal transduction were abundant in the biological process GO category. KEGG analysis revealed that plant hormone signal transduction and carotenoid biosynthesis were enriched out of the 127 total pathways. 12 DEGs involved in ABA biosynthesis and catabolism and 69 DEGs involved in plant hormone signal transduction were significantly regulated by root restriction. Twelve DEGs related to the biosynthesis and catabolism of ABA or plant hormone signal transduction were selected to validate the data obtained by RNA-Seq, and the results showed that genes such as PP2C, NCED, AAO3, ABA3, and CYP707A1, involved in ABA biosynthesis and signal transduction, may play important roles in the promotion of fruit quality by root restriction. This study suggests a potential ABA-mediated mechanism by which root-restriction cultivation promotes fruit ripening.