Molecular cloning and expression analysis of the mevalonate diphosphate decarboxylase gene from the latexof Hevea brasiliensis
2017
Wu, Chuntai | Li, Yu | Nie, Zhiyi | Dai, Longjun | Kang, Guijuan | Zeng, Rizhong
Mevalonate diphosphate decarboxylase (MVD) catalyzes the conversion of mevalonate diphosphate to isopentenyl diphosphate (IPP), a monomer of a large family of plant isoprenoids and cis-1,4-polyisoprene (natural rubber), which is present in most rubber-producing plants including Hevea brasiliensis (Para rubber tree). Here, we isolated the gene encoding MVD from the latex transcriptome of an elite rubber tree clone, Chinese Academy of Tropical Agriculture Sciences (CATAS) 7-33-97. The full-length cDNA of this gene, designated HbMVD, is 2032 bp long with a 1248-bp open reading frame (ORF) encoding a putative MVD of 415 amino acid residues with a theoretical molecular mass of 45.83 kDa and an isoelectric point (pI) of 6.52. Sequence alignment demonstrated that HbMVD cDNA shares 91 % identity with MVD genes from both Ricinus communis and Jatropha curcas. The genomic sequence of HbMVD is 11,749 bp long, comprising 10 exons and nine introns. The HbMVD promoter contains numerous cis-regulatory elements that are responsive to light, hormones, stress, and so on. Reverse-transcription quantitative PCR (qRT-PCR) revealed that HbMVD was most highly expressed in female flowers, followed by the bark, latex, male flowers, and leaves of untapped, mature rubber trees. The expression level of HbMVD in latex decreased progressively from the first, second, fourth, and third leaf stories of young shoots. Bark tapping (mechanical wounding), as well as exogenous ethephon and methyl jasmonate treatment, significantly upregulated HbMVD expression in the latex. This gene was upregulated in the bark and latex of tapping panel dryness (TPD)-affected trees but downregulated in latex from healthy, renewed bark. Further characterization of HbMVD would provide valuable insights into the involvement of HbMVD in regulating the biosynthesis of natural rubber and other IPP-derived isoprenoids in rubber tree.
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