Jasmonate signal induced expression of cystatin genes for providing resistance against Karnal bunt in wheat.

Two wheat varieties HD-29 (resistant, R) and WH-542 (susceptible, S) were pretreated with jasmonic acid (JA) or jasmonate and then artificially inoculated with sporidial suspension of Tilletia indica to study its influence in reducing Karnal bunt (KB) infection by regulating cystatin gene expression. JA was found to improve the plant defense against KB as its exogenous application resulted in decrease in coefficient of infection (CI) in both susceptible and resistant varieties following pathogen inoculation. Transcript profiling of wheat cystatin genes at different days after inoculation (DAI) showed that JA pretreatment positively induced cystatin gene expression in both varieties with greater induction of expression in resistant variety than the susceptible one (P< 0.05). Different temporal expression of three wheat cystatin genes, WC2, WC3 and WCMD was observed with their increased expression at 1DAI in the boot emergence stage which is most susceptible to KB and then slowly declined gradually at 3, 7 and 15 DAI in both the varieties. Except WC2, higher expression of other two cystatins viz. WC3 and WCMD at 1DAI showed higher response (P< 0.05) to KB pathogenesis at the disease-prone boot emergence stage as also evident by decrease of CI in both varieties. The results of determination of specific activity of cystatin by inhibitor assay were found to be consistent with those of transcript profiling. These findings suggest that jasmonic acid (JA) may act as a potential activator of induced resistance against Karnal bunt of wheat by upregulating cystatin gene expression.