Machanisms Of Membrane Anchor Protein MoOpy2 In Development And Pathogenicity Of Magnaporthe Oryzae

Rice blast disease,caused by the ascomycetous fungus Magnaporthe oryzae,is one of the most destructive fungal diseases of rice throughout the world,and annually results in significant rice yield losses worldwide.Therefore,it is important to carried out corresponding researches on the growth and development as well as the mechanism of pathogenicity in M.oryzae.In eukaryotic cells,MAPK signaling pathway,an important cell-mediated response,wildly exists in a variety of organisms.At present,five MAPK signaling pathways have been identified in Saccharomyces cerevisiae,and HOG MAPK pathway mainly regulates the response mechanism to extracellular osmotic stress.Among them,Opy2 is a transmembrane protein described as a membrane anchor,plays a crucial role in the signaling to HOG MAPK pathway.However,the biological function of Opy2 remains unclear.In this study,we characterized a membrane anchor protein Mo Opy2 in M.oryzae,a homolog of Opy2 in S.cerevisiae.Sequence analysis showed that Mo Opy2 has a transmembrane helix region at the N-terminus and four low complexity regions in the central part.Two mutants,named as Mo Opy2-17 and Mo Opy2-22,were acquired by targeted gene deletion in the wild-type strain Guy11 according to the principle of homologous recombination.Phenotypic analysis showed that the vegetative growth of the Mo Opy2 mutant is comparable to that of the Guy11,but its conidial production decreased.Further research found that the sensitivity of the mutants to cell wall stress increased,indicating that the loss of Mo Opy2 caused damage to cell wall integrity of M.oryzae.Microscope examination revealed that the Mo Opy2 mutants were defective in appressorium morphology,glycogen transfers,nuclear divisions and autophagic processes during appressorial formation.These evidences were closely related to the defects on appressorium penetration and invasive growth in Mo Opy2,and therefore attenuated the virulence on rice and barley.In conclusion,the above results revealed that the membrane anchor protein Mo Opy2 plays important roles in the growth and development,pathogenesis of M.oryzae.This study will provide support for the further functional characterization of Opy2 protein in filamentous fungi.