Pathogen-induced expression of chimeric chitinase gene containing synthetic promoter confers antifungal resistance in transgenic canola

Abstract

Controlling the expression of genes related to plant defense mechanisms is crucial when engineering plants with increased resistance to pathogens. In this study, synthetic promoters were placed upstream of a chimeric chitinase defense gene to produce transformation vectors. Canola plants were transformed with three constructs, pGDEC, pGMPC, pBISM2, containing synthetic promoters, synthetic pathogen-inducible promoter (SP-DDEE; parsley D and E17 elements + minimal promoter), SP-MP (minimal promoter), and the CaMV35S constitutive promoter, respectively. The results of reverse transcriptase PCR (RT-PCR) and enzyme activity assays show that the synthetic pathogen-inducible promoter (SP-DDEE) was responsive to the chitin and fungal elicitors, whereas negative control pGMPC did not respond. Furthermore promoters were assessed in the transgenic lines for antifungal activity against two phytopathogenic fungi. Results indicated that total proteins from transgenic lines carrying the SP-DDEE promoter when treated with elicitors strongly inhibited fungal growth, particularly Sclerotinia sclerotiorum, the major pathogen of canola. Overall, results indicate that not only was the SP-DDEE synthetic promoter highly responsive to the pathogen elicitors, but the inducible expression of the chimeric chitinase gene, when controlled by the SP-DDEE promoter, was also adequate to inhibit the fungal growth and development.