Functional Characterization Of The Sexual Reproduction Related Genes Fg307 And Fg970 In Fusarium Graminearum

Fusarium head blight(FHB),caused by Fusarium graminearum,is a significant disease among wheat production.It causes yield and quality losses due to sterility of the florets and formation of discoloured,blasted and grain weight-less.The ascospores formed in ruiting bodies(perithecia)are regarded as the primary inocula for FHB epidemics.In addition,discharged ascospores from perithecia facilitate the ropagation of disease during the flowering season.Therefore,the study of Fusarium graminearum sexual reproduction is important to direct control of FHB in wheat.In this thesis,we selected 296 unknown function genes through unknown function deletion mutants based on reverse genetics.All of the mutants were assayed for changes in sexual reproduction and 4 of them had defective in sexual development.Fg592 and Fg600 mutants were blocked in perithecium formation.The Fg307 and Fg970 deletion mutants produced normal-shaped perithecia,but the perithecium does not form normal cirrus.Both Fg307 and Fg970 were well conserved in ascomycetes but lack distinct ortholog in Saccharomyces cerevisiae and S.pombe.They had no conserved domain while there were several glycosylation site and conserved amino acids.Research on its biological characteristics,we found that deletion of the Fg307 and Fg970 genes had no effect on growth,conidiation,or colony morphology.The Fg307 and Fg970 mutants also was normal in stress responses.While no significant difference about virulence were observed in Fg307 and Fg970.However,they were defective in sexual reproduction.Eight days after sexual induction,mature perithecia forcibly discharge ascospores,and cirrhi of ascospores remain at the tip of ostioles.In contrast,Fg307 deletion mutants discharged a small amount ascospores and formed a vary small ascospore cirrhi.While Fg970 deletion mutants did not discharge ascospores and did not form any observable ascospore cirrhi.Moreover,when perithecia were squeezed,Fg307 mutant can only form 1-2 ascospore and most of the ascospores in Fg970 deletion mutants were found to have germinated inside the perithecium.In contrast,the wild-type and complemented strains had asci rosettes present to provide adequate separation.In addition,Fg307 and Fg970 displayed a drastic up-regulation during the sexual stage,which indicated that they played positive regulation in perithecium development.In conclusion,both Fg307 and Fg970 genes play important roles in sexual development.