Involvement of hsr203J like gene homologue, protease and protease inhibitors in triggering differential defense response against Alternaria blight in Brassica

Abstract

Transcript profiling of hsr203J, a known marker gene for Hypersensitive response (HR), was performed to delineate its role in differential defense against Alternaria brassicae in tolerant and susceptible genotypes of Brassica juncea. Reverse transcriptase (RT) PCR approach was utilized to investigate the correlation between expression of hsr203J like gene(s) and pathogenesis in stage dependent manner. It was revealed that the expression of hsr203J like gene increased as disease progressed from initial too late stage of infection in tolerant genotype. However, in susceptible genotype, its expression increased up to middle stage of infection with no expression in late stage of infection. In both genotypes, no expression of hsr203J like gene was observed in healthy leaves. It was observed that whereas three homologues of hsr203J like gene express at the late stage of infection in tolerant genotype, only single homologue of same expresses in susceptible genotype throughout all stages of infection. This indicates the role of hsr203J homologues in determining the differential defense response against Alternaria blight in Brassica. Determination of specific activity and in-gel assay revealed differential accumulation of protease and protease inhibitor in tolerant and susceptible genotypes at different stages of infection. Induction of differential protease and protease inhibitor activity appears to modulate the cell death during HR response to pathogen. Dissection of pathway leading to HR related cell death will enable us to know the molecular basis of disease resistance which will, in turn, help in engineering Brassica for resistance to Alternaria blight.