Functional characterization of LcTPS1 and LcTPS14 explains the biosynthesis of citronellol, citronellal and linalool in Lagerstroemia caudata

Abstract

Lagerstroemia caudata, a native species in China with a remarkable floral aroma, had been demonstrated the monoterpenoids as the main fragrant volatiles and integrated into crape myrtle breeding programs to enhance the aesthetic qualities. Terpene synthases (TPSs) were critical enzymes in terpenoids biosynthesis, which had not been isolated and reported in Lagerstroemia genus. Nine TPS genes were scrutinized from transcriptome data of L. caudata flowers, two of which, LcTPS1 and LcTPS14, were found gene expression mode aligned with the release pattern of floral scents, with subcellular localization showing LcTPS1 was expressed in plastids, while LcTPS14 in cytoplasm. Heterologous expression in E. coli revealed that LcTPS14 employed either geranyl pyrophosphate (GPP) or farnesyl pyrophosphate (FPP) to generate linalool or E-nerolidol. Over-expressing LcTPS1 or LcTPS14 in Arabidopsis increased the volatile terpenoids in flowers. Moreover, after virus-induced gene silencing (VIGS), the quantities of citronellal and citronellol dropped drastically in TRV - LcTPS1 samples, and TRV - LcTPS14 plants exhibited diminished linalool compared to controls. Our findings suggested LcTPS1 and LcTPS14 were pivotal in monoterpene production and had potentials in further molecular modulation of crape myrtle floral scents.