Transcription profile analysis for biosynthesis of flavor volatiles of Tunisian soft-seed pomegranate arils

Flavor is an important factor affecting the sensory of pomegranate and its products, which easily lose its freshness during processing and storage, but the biosynthesis of flavor-associated compounds is poorly understood until now. In this study, combining metabolome and transcriptome, flavor-associated attributes and volatile compounds of Tunisian pomegranate arils from 7 Chinese regions were studied. Depending on the different planting areas, there were significant differences in the content of sugars, organic acids and vitamin C. A total of 40 volatile compounds were characterized from all samples, of which 13 volatile compounds were common to all samples. There were 4 compounds showed higher contents in all samples, including 1-hexanol, (Z)-3-hexen-1-ol, α-terpineol, and 2,4-di-tert-butyl phenol. According to the Kyoto Encyclopedia of Genes and Genomes pathway analysis, 5 differential accumulated metabolites, including palmitic acid, octanoic acid, lauric acid, decanoic acid, and myristic acid, were significantly enriched in the fatty acid biosynthesis for all samples. Weighted gene co-expression network analysis revealed that 42 candidate flavor-associated differentially expressed genes and 9 transcription factors mainly located in 3 key modules. Hexanoic acid was an important metabolite, which was significantly correlated with 38 differentially expressed genes. Generally, complex regulatory networks were constructed in the study to identify structural genes and transcription factors which regulate the metabolism of volatile compounds in pomegranate. Our results provided new insights for understanding the difference in flavor biosynthesis and regulatory network of pomegranate arils.