The Function Research Of RdRP Related Genes In Fusarium Graminearum

Fusarium graminearum is the main pathogen of Fusarium head blight(FHB).F.graminearum can reduce the production of various host crops.More importantly,it can also produce a variety of mycotoxins,which will seriously affect the health of consumers.Sexual reproduction of F.graminearum plays an important role in the epidemic of FHB.The perithecium produced during the sexual stage can overwinter on infected wheat debris,and ascospores act as the primary inoculum and cause the primary infections during the flowering stage of wheat.Therefore,study on the sexual development of F.graminearum can provide new ideas and targets for the prevention and control of this disease.RNA-dependent RNA polymerases(RdRP)proteins are highly conserved in eukaryotes,widely exist in fungi and plants,and are important regulator of RNAi pathway.In this study,five RdRP protein-coding genes Fgrdrp1,Fgsad,Fgrdrp3,Fgrdrp4 and Fgrdrp5 in F.graminearum were knocked out by split-marker method.The single knockout mutants of these five genes and Fgsad/rdrp3 double knockout mutants were obtained,and their biological functions were explored..The main results are as follows:(1)The expression levels of Fgsad and Fgrdrp3 were significantly up-regulated during the asexual sporulation stage and the sexual perithecium maturation stage,while the expression levels of Fgrdrp1,Fgrdrp4 and Fgrdrp5 were not changed obviously during these stages.(2)In asexual stage,the deletion of these genes did not affect the mycelial growth rate,colony morphology,conidia production,and the virulence to wheat coleoptile.However,the length of conidia decreased slightly in the Fgsad knockout strain.Interestingly,the conidia length of the Fgsad/rdrp3 double knockout mutant was not significantly different from that of the wild-type PH-1.(3)In sexual stage,the deletion of these genes did not affect the production of perithecium,but the deletion of Fgrdrp1,Fgsad and Fgrdrp5 significantly reduced the number of cirrhis near the orifice of the perithecium and the ascospore discharge were decreased,especially in ΔFgsad.Further studies showed that the ascus development of the ΔFgrdrp1 strain was abnormal,and the mature ascospores in the ascus were significantly reduced.The ascus wall was dissolving much earlier in the ΔFgsad strain,and the ascospores could not be completely wrapped in ascus wall.The phenotype of the complementary transformant recovered,and there was no obvious different with the wild type.The ascospore discharge of ΔFgrdrp3 strain was normal,while the phenotype of ΔFgsad/rdrp3 double knockout mutant was almost the same as that of ΔFgsad,indicating that Fgrdrp3 did not play a role in this process.Some of the ascospores ofΔFgrdrp5 strain were defective in development and had irregular shapes,which may be the main reason for the decrease of ascospore discharge.In summary,Fgrdrps play important roles in the sexual reproduction stage of F.graminearum,but the mechanism needs to be furher studied.