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

Abstract

<p>β-1,3-glucanases play a major role in combating the abnormal leaf fall disease (ALF) caused <br>by the oomycete Phytophthora spp. in Hevea brasiliensis, the major commercial source <br>of natural rubber. In this study, partial sequences of four novel promoters of different<br>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<br>β-1,3-glucanase genes driven by a different set of promoter sequences in a single clone <br>of Hevea. The nucleotide sequencing revealed the presence of 913, 582, 553 and 198 bp <br>promoter regions upstream to the translation initiation codon, ‘ATG’, and contained the <br>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 <br>nucleosome formation potential and in two of the promoters CpG islands were observed <br>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) <br>fusion binary vectors through Agrobacterium mediated transformation in Hevea callus and <br>tobacco. GUS gene expression was noticed in Hevea callus indicating that all the promoters <br>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 <br>can be utilized for defense specific gene expression in future genetic transformation attempts in Hevea and in a wide variety of plant systems.<br></p><p><br>Keywords: abnormal leaf fall, Hevea brasiliensis, Phytophthora, PR-protein, systemic acquired resistance (SAR), β-1,3-glucanase<br></p>