Characterization of Brassica juncea–Alternaria brassicicola interaction and jasmonic acid carboxyl methyl transferase expression

The mode of disease progression during Alternaria brassicicola infection, a prototype of necrotrophic fungal infection, was studied in mustard, Brassica juncea. During the disease advancement in mustard after infection with A. brassicicola, production of reactive oxygen species occured within 16 to 24 h in B. juncea cells. Severe necrosis was observed after 2 days of infection in B. juncea leaves with the development of necrotic DNA. The transcriptional activation of jasmonic acid carboxyl methyl transferase (JMT) was observed after 2 days post infection with A. brassicicola. Differential expression of JMT was observed in various tissues of mustard with the detection of the protein in mustard leaves only after treatment with jasmonic acid, but always found in young buds and to a lesser extent in opened flowers. Since JMT is involved in positive feedback regulation of jasmonate pathway and the jasmonic acid responsive genes, it could be a good target for achieving resistance against necrotrophic pathogens.