New insights into the novel and functional promoter sequences of β-1,3-glucanase gene from Hevea brasiliensis

Abstract

β-1,3-glucanases play a major role in combating the abnormal leaf fall disease (ALF) caused by the oomycete Phytophthora spp. in Hevea brasiliensis, the major commercial source of natural rubber. In this study, partial sequences of four novel promoters of different β-1,3-glucanase genomic forms were amplified through inverse PCR from the H. brasiliensis clone RRII 105 and sequence characterized. This is the first report showing β-1,3-glucanase genes driven by a different set of promoter sequences in a single clone of Hevea. The nucleotide sequencing revealed the presence of 913, 582, 553 and 198 bp promoter regions upstream to the translation initiation codon, ‘ATG’, and contained the essential cis-elements that are usually present in biotic/abiotic stress-related plant gene promoters along with other complex regulatory regions. The amplified regions showed strong nucleosome formation potential and in two of the promoters CpG islands were observed indicating the tight regulation of gene expression by the promoters. The functional efficiency of the isolated promoter forms was validated using promoter: reporter gene (GUS) fusion binary vectors through Agrobacterium mediated transformation in Hevea callus and tobacco. GUS gene expression was noticed in Hevea callus indicating that all the promoters are functional. The transgenic tobacco plants showed no GUS gene expression. The implication of these novel promoter regions to co-ordinate the β-1,3-glucanase gene expression can be utilized for defense specific gene expression in future genetic transformation attempts in Hevea and in a wide variety of plant systems.

Keywords

• abnormal leaf fall
• hevea brasiliensis
• phytophthora
• pr-protein
• systemic acquired resistance (sar)
• β-1
• 3-glucanase