Metabolomic and transcriptomic analyses of monoterpene biosynthesis in Muscat and Neutral grape hybrids

Monoterpenes are typical aroma components of muscat grape ( Vitis vinifera L.) cultivars. However, differences in the molecular mechanism of monoterpene biosynthesis between Muscat and non -Muscat grapes remain unclear. Here, comprehensive transcriptomic and metabolomic analyses of two F1 hybrids with different aroma profiles obtained from crosses between ' Muscat Hamburg ' and ' Red Globe ' grapes were performed to examine the unique monoterpene accumulation pattern and related candidate genes. The concentrations of most monoterpenes differed at various times, in the hybrid progeny, increasing from the pre-veraison stage to the veraison stage, followed by a decreasing trend from veraison to maturity. Within the F1 generation, the concentrations of accumulated monoterpenes were significantly higher in Muscat grapes than in neutral grapes. Furthermore, linalool, alpha-terpineol, and l- alpha-terpineol may be important odorants affecting the floral characteristics of Muscat grapes due to their high odor activity values. Transcriptional analysis identified three VvDXS (LOC100249323, LOC100268079, and LOC100247834), 1 VvHDS (LOC100257071), one VvMVK (LOC100251148), one VvHMGR (LOC100265082), and one VvGGPPS (LOC100257234) genes encoding proteins involved in the MEP and MVA pathways. Eleven TPS genes potentially involved in monoterpene regulation were also 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 genes encoding transcription factors. The findings in this study provide new insights for further functional validation and investigation of genes related to monoterpene synthesis in Muscat aroma grapes.