Integrated transcriptomic and volatilomic profiles to explore the potential mechanism of aroma formation in Toona sinensis

As an important quality determinant of Toona sinensis, the unique aroma largely impacts the purchasing behavior of consumers. However, the underlying formation mechanism of the characteristic aroma of T. sinensis remains poorly understood. In this work, integrative volatile/nonvolatile compounds profiling and RNA sequencing were used to characterize six T. sinensis cultivars. Volatile sulfur compounds (VSCs) and terpenoids were the main volatile organic compounds (VOCs) in T. sinensis, accounting for 36.95-67.27% and 17.75-31.36% of the total VOC content, respectively. Notably, the VOCs originated from terpenoid biosynthesis, and the degradation of unsaturated fatty acids (UFAs) played important roles in reconciling the irritating odor of VSCs. The above differential metabolic profiles are the main sources of the specific aroma of different T. sinensis cultivars. Furthermore, 13 volatile organic compounds were identified as potential biomarkers to distinguish these T. sinensis cultivars by chemometric analysis. Based on the analysis of transcriptomic datasets, the potential biosynthetic pathways of the key VSCs were firstly confirmed in T. sinensis. It was found that 1-propenylsulfenic acid is a crucial precursor in the formation of characteristic VSCs in T. sinensis. Additionally, two potential mechanisms were proposed to explain the differences of the key VSCs among six T. sinensis cultivars. These results provide theoretical guidance for improving the aroma quality of T. sinensis.

Automated summary

As an important quality determinant of Toona sinensis, the unique aroma greatly influences consumer purchasing behavior. Despite this, the formation mechanism of the characteristic aroma in T. sinensis is not well understood. This study used volatile/nonvolatile compound profiling and RNA sequencing to characterize six T. sinensis cultivars. Key volatile organic compounds (VOCs) in T. sinensis were found to be volatile sulfur compounds (VSCs) and terpenoids. The differential metabolic profiles of these compounds contribute to the distinct aroma of different T. sinensis cultivars. Chemometric analysis identified 13 VOCs as potential biomarkers for distinguishing these cultivars. Transcriptomic analysis confirmed the biosynthetic pathways of key VSCs in T. sinensis, with 1-propenylsulfenic acid identified as a crucial precursor. Two potential mechanisms for the differences in key VSCs among cultivars were proposed. These findings provide theoretical guidance for improving the aroma quality of T. sinensis.