Functional genomics reveals functions of terpene synthases for volatile terpene formation in peach

Abstract

Terpenes are important volatile organic compounds (VOCs) impacting fruit aroma and flavor quality. Terpene synthases (TPSs) are the key enzymes responsible for the biosynthesis of basic backbone structure of terpenes. Here, we show that genome of cultivated peach (Prunus persica L. Batsch) contains 38 TPS genes, with 24 members in the TPS-a cluster. Transcriptome analysis showed that the expression of PpTPSs in peach fruits was regulated by environmental factors such as UV-B light and low temperature, as well as by phytohormones such as ethylene and MeJA. After analyzing the expression of 38 PpTPSs in peach fruit developmental stages and different tissues, we screened and cloned six new highly expressed TPS genes. Subcellular localization showed that PpTPS13 and PpTPS23 were localized in the plastid, while PpTPS12, PpTPS22, PpTPS25 and PpTPS28 were localized in the cytoplasm. Heterologous expression of PpTPSs in Escherichia coli followed by the enzymatic assays revealed that only four TPSs (PpTPS12, PpTPS22, PpTPS25 and PpTPS28) were active in vitro. Using GPP and FPP as substrates, respectively, these PpTPSs were able to synthesize an array of volatile terpenes, including 15 monoterpenes such as geraniol, camphene, pinene, borneol and phellandrene, and 14 sesquiterpenes such as farnesene, nerolidol and α-bergamotene. Our results provide target genes for engineering to enhance production of volatile terpenes and thereby to improve fruit quality.