In eukaryotes,the translation initiation factor eIF3 consists of 5-13 subunits,which including eIF3a,eIF3b,eIF3c,eIF3d,eIF3e,eIF3f,eIF3g,eIF3h,eIF3i,eIF3j,eIF3k,eIF3l and eIF3m.Hcr1 is a homologous protein of eIF3j which plays an important role in the translation process by independently or as a component of the eIF3 complex to participate in regulating the ribosome biosynthesis,translation initiation,translation termination and ribosome cycling in translation.At present,the role of translation initiation factors,especially their subunits in the development and pathogenesis of filamentous phytopathogenic fungi remains still unclear.Moreover,the biological function of MoHcr1,a homologous protein related to Hcr1,is not documented in Magnaporthe oryzae.The analysis of the function of MoHcr1 is helpful to clarify the mechanism of the influence of translation initiation factor eIF3 on the growth and development of M.oryzae,and lay an important experimental basis for exploring potential new drug targets.In this study,the function of MoHcr1 in regulating the development and pathogenicity of M.oryzae was analyzed,and the following results were obtained:To explore the biological function of MoHcr1 in M.oryzae,theΔMoHcr1 mutant which showed resistance to hygromycin was obtained using the Agrobacterium-mediated transformation of M.oryzae wild-type Guy11.Phenotypic analysis showed thatΔMoHcr1mutant showed defects on vegetative growth.The growth rate of the mutant decreased significantly on the four nutrient media,the colony of the mutant grew upward with protrusions,and the aerial hypha were denser than Guy11.Both the hyphae branches and septa of theΔMoHcr1 mutant increased significantly,the chitin content of the hyphal tip of the mutant significantly decreased with a defective polar growth.The conidiation and numbers of conidiophores of the mutant decreased significantly.The conidial morphology of mutant is abnormal,with decreased numbers of septa in conidia.TheΔMoHcr1 mutant significantly decreased the pathogenicity on the barley and rice plants,with smaller diseased lesions and decreased number of diseased spots.Further experiments showed that the mutant displayed much weaker ability to degrade the reactive oxygen species than that of by the wild type.The conidial germination rate of the mutant was higher than that of wild-type,but the appressorium formation rate was decreased.The cell wall integrity of the appressorium of the mutant was impaired,and the collapse rate was much higher than that of the wild type after treatment with different concentrations of glycerol.There were no significant differences in the storage of glycogen and lipid in the conidia,and both the glycogen and lipid showed normal degradation during conidia germination,compared with the wild type Guy11.The growth of the mutant showed significant differences in the MM-N media with different nitrogen sources,compared with the wild type Guy11.The growth rate of the mutant on plates with NH4+and Glutamic acid as the only nitrogen source increased significantly,compared to wild type Guy11.However,the growth of the mutant decreased significantly on plates with Asparagine as the only nitrogen source.The sensitivity assays showed that theΔMoHcr1 mutant significantly increased the sensitivity to cell wall stressors CFW and CR,decreased the sensitivity to osmotic stress factors Na Cl and KCl,and almost no alteration of sensitivity to Sorbitol,Caffeine and SDS,compared to wild type Guy11.Subcellular localization showed that MoHcr1 was localized to the cytoplasmic ribosomes outside the nucleus and vacuoles.In summary,MoHcr1 is an important regulator and involved in the fungal growth and pathogenicity of M.oryzae. |