Metabolomic and Transcriptomic Analysis of Monoterpene Biosynthesis in Muscat and Neutral Grape Hybrids

Monoterpenes are typical aroma components of muscat grape cultivars. However, the molecular mechanism of monoterpene biosynthesis between muscat and non-muscat grape remains unclear. In this study, two F1 hybrids with different aroma profiles from the cross between 'Midknight Beauty' and 'Red Globe' grapes were chosen for comprehensive transcriptome and metabolome analysis to study the unique monoterpenoid accumulation pattern and related candidate genes. The results showed that in the hybrid progeny, the concentrations of most terpenoids differed at different times, and the concentration of most terpenoids increased from the pre-veraison to veraison, followed by a decreasing trend from veraison to maturity. In the F1 generation, the concentration of monoterpenes accumulated in Muscat grapes was significantly higher than that in Neutral grapes. Furthermore, linalool，α-terpineol, and L-α-terpineol may be important odorants that affect the floral characteristics of Muscat grapes because of their high odor activity values (OAVs). Transcriptional analysis identified 3 VvDXS (LOC100249323, LOC100268079, LOC100247834), 1 VvHDS (LOC100257071), 1 VvMVK (LOC100251148), 1 VvHMGR (LOC100265082), and 1 VvGGPPS (LOC100257234) in the MEP and MVA pathways. Meanwhile, 11 TPS genes that may be involved in the regulation of monoterpenes were identified. Among them, VvTPS (LOC100853562) showed consistency with the accumulation of monoterpenes and had a high expression level， MYB (LOC100255488), GATA (LOC100262474), and ERF (LOC100255943, LOC100260401) were selected as candidate transcription factors (TFs). The findings provide new insights for the subsequent functional validation and further investigation of genes related to monoterpene synthesis in Muscat aroma grapes. Skin mRNA profiles of E-L 34, E-L 37, and E-L 38 stages Muscat type and Neutral type / 'Midknight Beauty' grape and 'Red Globe' grape cross-group