Comprehensive study of volatile compounds and transcriptome data providing genes for grape aroma

Abstract

Background: Fruit aroma is an important quality with respect to consumer preference, but the most important aroma compounds and their genetic regulatory mechanisms remain elusive.

Results: In this study, we qualitatively analysed volatile compounds in the pulp and skin of five table grape cultivars with three aroma types (muscat, strawberry, and neutral) using solid-phase microextraction gas chromatography/mass spectrometry. We identified 215 aroma compounds, including 88 esters, 64 terpenes, and 29 alcohols, and found significant differences in the number of compounds between the pulp and skin, especially for terpenes. Skin transcriptome data for the five grape cultivars were generated and subjected to aroma compound-gene correlation analysis. The combined transcriptomic analysis and terpene profiling data revealed 20 candidate genes, which were assessed in terms of their involvement in aroma biosynthetic regulation, including 1 VvCYP (VIT_08s0007g07730), 2 VvCCR (VIT_13s0067g00620, VIT_13s0047g00940), 3 VvADH (VIT_00s0615g00010, VIT_00s0615g00030, VIT_ 00s0615g00020), and 1 VvSDR (VIT_08s0040g01200) in the phenylpropanoids synthesis pathway, and 1 VvDXS (VIT_05s0020g02130) and 6 VvTPS (VIT_13s0067g00370, Vitis_vinifera_newGene_3216, VIT_13s0067g00380, VIT_13s0084g00010, VIT_00s0271g00010, and VIT_13s0067g00050) in the methylerythritol phosphate pathway (involved in the production and accumulation of aromatic compounds). Additionally, 2 VvMYB (VIT_17s0000g07950, VIT_03s0063g02620) and 1 VvGATA (VIT_15s0024g00980) transcription factor played important regulatory roles in the accumulation of key biosynthetic precursors of these compounds in grapes. Our results indicated that downstream genes, specifically 1 VvBGLU (VIT_03s0063g02490) and 2 VvUGT (VIT_17s0000g07070, VIT_17s0000g07060) are involved in regulating the formation and volatilization of bound compounds in grapes.

Conclusions: The results of this study shed light on the volatile compounds and "anchor points" of synthetic pathways in the pulp and skin of muscat and strawberry grapes, and provide new insight into the regulation of different aromas in grapes.

Keywords: Aroma; Grapes; SPME-GC-MS; Transcriptome; Volatile compounds.