RNA-seq and GC/MS analyses provides new insights in the metabolically engineered “Bronze” tomato

The metabolically engineered “Bronze” tomato is characterized by the constitutive overexpression of the VvStSy gene, which encodes a structural protein responsible for the biosynthesis of resveratrol and related stilbenoids, and the fruit-specific overexpression of the AmDel/Rosea1 and AtMYB12 genes encoding transcription factors that activate the polyphenol biosynthetic pathway. This tomato line is characterized by high levels of polyphenols (anthocyanins, flavonols and stilbenoids) in ripe fruits and has been associated with antioxidant and anti-inflammatory effects in vivo. 1673 In this study, an RNA-seq analysis was carried out to understand the differences between the transcriptomic profiles of “Bronze” ripe fruits compared to WT tomato fruits. The RNA-Seq analysis yielded 779 up-regulated and down-regulated differentially expressed genes (DEGs). The annotated DEGs were enriched for genes mainly involved in genetic information processing, carbohydrates and energy metabolism, signaling and cellular processes, amminoacids metabolism, and biosynthesis of secondary metabolites (mainly phenylpropanoid and flavonoid). Interestingly, our results also showed DEGs involved in monoterpenoid biosynthesis and lipid metabolism, which paralleled the GC/MS analyses carried out on the WT and “Bronze” fruits. GC/MS results indicated higher levels of volatile organic compounds (VOCs) belonging to terpenoid classes in “Bronze” tomato fruits, compared to the WT fruits, which mostly produced VOCs belonging to aldehydes and alcohol groups in the three analyzed ripening stages. Therefore, our study highlights key metabolic and transcriptomic changes and identifies, in addition to a higher polyphenol content, a further bioactive potential derived from terpenoid compounds in the “Bronze” tomatoes.