Investigation of Fire Blight Susceptibility and Iron Homeostasis of Pear (Pyrus communis L.) Following Invasion of Tissues by hrpW-, hrpN- and dspA/E- Mutants of Erwinia amylovora

Erwinia amylovora, the causal agent of fire blight disease in rosaceous plants, contains type III secreted effector proteins including DspA/E, HrpN and HrpW, which are secreted into host plants during the pathogenicity stages. In order to investigate the role of these effector proteins in the interaction with the host plants, susceptible (Bartlett), tolerant (Harrow Sweet) and resistant (Dargazi) pear cultivars were inoculated with wild-type and mutant strains of E. amylovora (hrpW-, hrpN- and dspA/E-) under in vitro conditions. Based on the results, HrpW protein may be involved in pathogenicity in Dargazi cultivar. Different levels of pathogenicity were observed by dspA/E- mutant in cultivars. The results showed the key role of HrpN in the defense mechanisms of Dargazi cultivar, and its pathogenic role in Harrow Sweet and Bartlett cultivars. An increase in ferritin levels was observed in all cultivars inoculated with the wild type strain, but resistant and tolerant cultivars showed higher ferritin levels and a decrease in Fe2+ was observed only in these cultivars. The obtained data show that the HrpW protein does not affect iron homeostasis. Inoculation of Harrow Sweet and Dargazi cultivars with all strains increased ferritin, which was associated with a decrease in Fe2+. Based on the results, it is not possible to associate any of the effector proteins with changes in ferritin and Fe2+. In general, the ability of resistant pear cultivars to increase ferritin levels and regulation of iron can be one of the reasons for their resistance to fire blight. According to the results, different mechanisms are employed by pear cultivars to respond to the causative agent of fire blight.

Investigation of Fire Blight Susceptibility and Iron Homeostasis of Pear (Pyrus communis L.) Following Invasion of Tissues by hrpW-, hrpN- and dspA/E- Mutants of Erwinia amylovora Keywords:

cv. Bartlett , cv. Dargazi , cv. Harrow sweet , Effector proteins.