Changes in ethylene perception of Arabidopsis plants lead to differential responses during infection by Verticillium dahliae

Preliminary studies on the susceptibility of several Arabidopsis mutants to the soil-borne pathogen Verticillium dahliae showed that the etr1-1 (ethylene insensitive) mutants had enhanced disease tolerance compared to the control (Col-0 ecotype) or other mutant lines tested. In order to investigate the possible role of ethylene in plant defence mechanisms, Arabidopsis plants mutated in the ethylene perception pathway (ein2, ein3, ein4 and ein5) were used along with the etr1-1 plants in pathogenicity tests with V. dahliae. It was revealed that the etr1-1 plants showed less disease severity compared to the other ethylene mutants. Furthermore, fungal biomass quantified by Real-time PCR (RT-PCR) was significantly less in the etr1-1 plants than that of all the other mutants. To obtain a further insight in the defence mechanisms that could be involved in this phenomenon, the expression of PR1, PR2, PR5, PDF12, WREY 18, 22, 33, 40, 53 and 60, ERF1, ERF2, AtMYC2, rd22, VSP2, ABI1, KIN1, SDR1, GSL5, GSTF8 and UGT73B1 genes that have been associated with defence mechanisms in plants against pathogens, was studied using RT-PCR. The expression of genes GSTF8, SDR1 and KIN1 was elevated in the etr1-1 plants, suggesting a possible role in the defence of plants against V. dahliae.