Differential induction of NPR1 during defense responses in Brassica juncea

We have cloned an NPR1-homolog from mustard and found that NPR1 transcript level was elevated in mustard leaves upon treatment with salicylic acid (SA) and during infection with biotrophic fungal pathogen Erysiphe cruciferarum. Conversely, necrotrophic fungal pathogen Alternaria brassicicola, which caused severe tissue necrosis had apparently no effect on BjNPR1 expression. During these challenges the differential activation of SA and jasmonic acid responsive defense pathways was detected using marker genes PR1, defensin and AOC. The BjNPR1 protein was detected as high molecular weight oligomeric and reduced monomeric forms. We identified a monopartite NLS at the C-terminus of BjNPR1 amino acid sequence and transient transformation with NPR1-GFP fusion construct revealed nuclear translocation of BjNPR1 protein upon induction with SA.