Identification and expression analysis of the <Emphasis Type="Italic">Eucommia ulmoides</Emphasis> farnesyl diphosphate synthase gene family to reveal the key gene involved in rubber biosynthesis

Eucommia ulmoides Oliver is rich in trans-polyisoprene rubber (Eu-Rubber), a high-molecular mass polymer of isoprene units with a trans-configuration. Farnesyl diphosphate (FPP) synthase (FPS) is a key enzyme, which involved in the production of important precursors of different terpenoids. In this study, we cloned and characterized five novel FPS genes from E. ulmoides. The full-length synthases were named EuFPS1-5 and their deduced amino acid sequences exhibited high homology to those from other plant isoforms. EuFPS1 and EuFPS4 were observed to be highly expressed in leaves, EuFPS2 and EuFPS3 were present at low levels in leaves and fruit throughout the plant development, and EuFPS5 was highly expressed exclusively in young fruit. Expression of EuFPS5 correlated with the accumulation rate of Eu-Rubber and might be responsible for it. This study is expected to enhance our understanding of the role of EuFPSs in biosynthesis and regulation of useful secondary metabolites in E. ulmoides.