Gene coexpression network for -1,4-polyisoprene biosynthesis involving mevalonate and methylerythritol phosphate pathways in Oliver.

, a deciduous dioecious plant species, accumulates -1,4-polyisoprene (TPI) in its tissues such as pericarp and leaf. Probable TPI synthase (-isoprenyl diphosphate synthase ()) genes were identified by expressed sequence tags of this species; however, the metabolic pathway of TPI biosynthesis, including the role of s, is unknown. To understand the mechanism of TPI biosynthesis at the transcriptional level, comprehensive gene expression data from various organs were generated and TPI biosynthesis related genes were extracted by principal component analysis (PCA). The metabolic pathway was assessed by comparing the coexpression network of TPI genes with the isoprenoid gene coexpression network of model plants. By PCA, we dissected 27 genes assumed to be involved in polyisoprene biosynthesis, including genes, genes encoding enzymes of the mevalonate (MVA) pathway and the 2--methyl-D-erythritol 4-phosphate (MEP) pathway, and genes related to rubber synthesis. The coexpression network revealed that 22 of the 27 TPI biosynthesis genes are coordinately expressed. The network was clustered into two modules, and this was also observed in model plants. The first module was mainly comprised of MEP pathway genes and gene, and the second module, of MVA pathway genes and gene. These results indicate that TPI is likely biosynthesized by both the MEP and MVA pathways and that gene expression is differentially controlled by these pathways.