Molecular characterization and expression analysis of two farnesyl pyrophosphate synthase genes involved in rubber biosynthesis in Hevea brasiliensis

Abstract

Farnesyl pyrophosphate synthase (FPS) catalyzes the formation of farnesyl pyrophosphate from dimethylallyl pyrophosphate, which is an important precursor of terpenoids, such as polyisoprenoid, in rubber-producing plants. In this paper, two genes encoding FPSs, FPS1 and FPS2, were isolated from Hevea brasiliensis using PCR. The full-length cDNAs of HbFPS1 and HbFPS2 are 1320 and 1324bp, respectively; both contain 1026-bp open reading frames that encode a polypeptide of 342 amino acid residues. They share 87% and 83% (HbFPS1), and 78% and 78% (HbFPS2) amino acid identities with the FPSs of Eucommia ulmoides and Parthenium argentatum, respectively. There is a 91% amino acid identity between HbFPS1 and HbFPS2. HbFPSs prefer T-ended codons for amino acids and have a strong asymmetric mutation bias. The genomic sequences of HbFPS1 and HbFPS2 are 7799 and 11,345bp, respectively, both comprising 12 exons and 11 introns. The HbFPS promoters contain multiple cis-regulatory elements involved in responsiveness to light, hormones and stress. Quantitative RT-PCR analyses showed that HbFPS mRNAs were present in all of the organs of mature virgin rubber plants, but their transcripts were most abundant in the reproductive organs. High expression levels of individual genes in the leaf levels of young shoots at particular positions suggested important roles for laticifer differentiation in different phases of stem bark development. HbFPS expression levels were significantly upregulated in the latex after bark tapping and exogenous ethephon or methyl jasmonate treatments. Both genes were upregulated in the latex of severely tapping panel dryness-affected trees but were downregulated in the latex from healthy and slightly affected bark. Thus, the two HbFPS genes may play essential roles in cis-1,4-polyisoprene synthesis in rubber trees, which would provide the basis for their further functional dissection.