Function Analysis Of MoRAD26 And MoMEC1 In DNA Damage Repair And Pathogencity Of Magnaporthe Oryzae

Rice blast caused by the filamentous fungus Magnaporthe oryzae is one of the most serious diseases in rice production.Depicting the pathogenic molecular mechanism of the rice blast fungus is significant for the control of rice blast disease in practice.In various organisms,the stability and integrity of genomic DNA are threaten by the influence of external environmental factors,internal metabolism,or other complicate factors.In response to these threatens,organisms can activate different DNA damage repair pathways such as the DDR signal cascade pathway to respond to different types of DNA damage.In addition,activation of DDR signaing may cause autophagy to occur.In M.oryzae,autophagy plays important roles in growth,appressorium formation and successful infection of host cells.So far,in plant pathogenic fungi,there are few studies on the mechanism of DNA damage and DNA damage-mediated autophagy.In this study,through the prediction of the AIM domain,two genes Mo RAD26 and Mo MEC1,which contain AIM domain and may potentially affect autophagy,were found.Based on the principle of homologous recombination,these two genes were knocked out and biological phenotypes of the gene deletion mutant strain were investigated,respectively.The experiment results showed that the deletion of the Mo RAD26 gene leads to no obvious effect on the growth,sporulation and appressorium formation in M.oryzae.However,ΔMorad26 was significantly reduced in pathogenicity.Further analysis revealed that the knockout of Mo RAD26 gene impaired the penetration peg formation and the invasive hypha expansion,and resulted in more sensitive to H₂O₂,HU and MMS.In addition,under nitrogen starvation,the autophagy level inΔMorad26 slightly increased compared with that of wild type.In contrast,the deletion of Mo MEC1 gene resulted in slower growth,fewer conidia,delayed appressorium formation,higher sensitivity to H₂O₂,HU,and MMS in comparison with WT.Interestingly,disruption of Mo MEC1slightly reduced the pathogenicity of rice blast fungus.Furthermore,it was found that the autophagy level inΔMomec1 was significantly increased compared with that of wild type under the induction of DNA damage reagents,while the autophagy level was slightly increased under nitrogen starvation.Taken together,two putative protein kinases Mo Rad26 and Mo Mec1 were preliminarily explored in M.oryzae,and their important roles in the process of genome stability and autophagy of M.oryzae were clarified.Our results would provide theoretical basis for the control of rice blast and make a reference for the research on the relationship between DNA damage and autophagy in other filamentous fungi.