Functional Study Of UvustA?UvPmk1 And UvCDC2 Genes In Ustilaginoidea Virens

Rice false smut is a kind of rice panicle disease caused by the fungal pathogen Ustilaginoidea virens.The study on its pathogenic mechanism is of great significance to understand the interaction between rice and pathogens and to find a new chemical control target.In this study,the functional analysis of the gene UvustA,UvPmk1 and UvCDC2 was performed,and the main results are as follows:1.The function of the ustiloxin synthesis gene UvustA was analyzed to verify whether UvustA is involved in the synthesis of ustiloxin A.The study found that the gene UvustA knockout transformant and the complementary transformant showed no significant differences in colony growth rate,sporulation and pathogenicity on the rice.Qualitative analysis of Ustiloxin A in false smut ball by wild-type strains,knock-out transformants and transformants deleting UvustA signal peptide by LC-MS revealed that Ustiloxin A existed in the false smut ball formed by inoculating wild-type strains.The presence of Ustiloxin A was not detected in the false smut ball formed by knocking out the transformant and the transformant deleting the UvustA signal peptide;through signal peptide prediction,fusion protein expression localization and western blotting analysis,it was found that UvustA is a secreted protein,which can be secreted into the extracellular.The putative gene UvustA is speculated to participate in the formation of Ustiloxin A,but it is not related to false smut ball formation.2.The function of the gene UvPmk1 was analyzed.The analysis found that the deletion of the UvPmk1 gene caused the sporulation decreased significantly.It shows higher tolerance to osmotic stress and cell wall integrity.When the knockout transformants was used to inoculate the rice seedlings at the booting stage,the hyphae on the outer surface of the glumes were relatively few and the growth was inhibited,and it could not spread to the inside of the floret,to form a false smut ball.Inoculation with wild-type and complementary transformants,the incidence of rice false smut reached 90%,and the average number of grains per panicle was 35.7 and28.4 respectively.The results indicated that the UvPmk1 gene could regulate the sporulation and pathogenesis of Ustilaginoidea virens.3.The analysis of the function of gene UvCDC2 showed that the knockout transformant of UvCDC2 gene have no significant differences in colony morphology,growth rate and spore morphology compared with the wild type,but the sporulation decreased by 75%.Tolerance to different environmental stresses was enhanced.Inoculation with the knockout transformant spore hyphal suspension,the rice false smut ball could not be formed.There were no significant differences in growth phenotype,stress resistance and pathogenicity between wild type and complementary transformants.The results indicated that the UvCDC2 gene is involved in sporulation and pathogenicity of Ustilaginoidea virens.