Abstract
Muscadine grapes accumulate higher amounts of bioactive phenolics compared with other grape species. To identify the molecular events associated with polyphenolic accumulation that influence antioxidant capacity, two contrasting muscadine genotypes (C5 and C6) with varied phenolic/flavonoid content and antioxidant activity were investigated via RNA-sequencing during berry development. The results showed that berry development is concomitant with transcriptome profile changes, which was more pronounced at the véraison (V) stage. Despite that the downregulation pattern of gene expression dominated the upregulation through berry development, the C5 genotype maintained higher expression levels. Comparative transcript profiling allowed the identification of 94 differentially expressed genes with potential relevance in regulating fruit secondary metabolism, including 18 transcription factors and 76 structural genes. The genes underlying the critical enzymes in the modification reactions of polyphenolics biosynthetic pathway, including hydroxylation, methylation, and glycosylation were more pronounced during the immature stages of prevéraison (PrV), V, and postvéraison (PoV) in the C5 genotype, resulting in more accumulation of biologically active phenolic/flavonoid derivatives. The results suggested that muscadine grapes, as in bunch grapes (Vitis sp.); possess a similar mechanism that organizes polyphenolics accumulation; however, the set of total flavonoids (TFs) and structural genes coordinating the pathway varies between the two species.
Highlights
Grapevine is a member of the large genus Vitis that is divided into two subgenera with a varying number of somatic chromosomes (Olien, 1990)
Our previous work built an extensive classification of metabolome profile throughout the six berry developmental stages of contrasting C5 and C6 muscadine genotypes, showing an apparent reduction in the total phenolic content (TPC) and total flavonoid content (TFC) along with the progression in berry development
The data indicated that transcriptional modulation of a large number of genes occurs during berry development
Summary
Grapevine is a member of the large genus Vitis that is divided into two subgenera with a varying number of somatic chromosomes (Olien, 1990). Muscadine berries display enhanced nutraceutical value due to the accumulation of distinctive phytochemical constituents that have a great potential activity against several chronic diseases (Bralley et al, 2007; God et al, 2007; Mellen et al, 2010; Gourineni et al, 2012; Luo et al, 2017; Mendonca et al, 2019) Such nutritional and health merits are restricted to muscadine, but muscadine berries accumulate higher amounts of bioactive polyphenolics compared with other grape species (Pastrana-Bonilla et al, 2003; You et al, 2012; Mendonca et al, 2019)
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