Integrative Analyses of Metabolomes and Transcriptomes Provide Insights into Flavonoid Variation in Grape Berries

Flavonoids in grapes contribute the
quality of the berry, but the
flavonoid diversity and the regulatory networks underlying the variation
require a further investigation. In this study, we integrated multi-omics
data to systematically explore the global metabolic and transcriptional
profiles in the skins and pulps of three grape cultivars. The results
revealed large-scale differences involved in the flavonoid metabolic
pathway. A total of 133 flavonoids, including flavone and flavone C-glycosides, were identified. Beyond the visible differences
of anthocyanins, there was large variation in other sub-branched flavonoids,
most of which were positively correlated with anthocyanins in grapes.
The expressions of most flavonoid biosynthetic genes and the major
regulators MYBA1 were strongly consistent with the
changes in flavonoids. Integrative analysis identified two novel transcription
factors (MYB24 and MADS5) and two
ubiquitin proteins (RHA2) as promising regulatory
candidates for flavonoid biosynthesis in grapes. Further verification
in various grape accessions indicated that five major genes including flavonol 3′5′-hydroxylase (F3′5′H), UDP-glucose:flavonoid 3-O-glycosyl-transferase, anthocyanin O-methyltransferase, acyltransferase (3AT), and glutathione S-transferase (GST4) controlled flavonoid variation in grape
berries. These findings provide valuable information for understanding
the mechanism of flavonoid biosynthesis in grape berries and the further
development of grape health products.