Functional Analysis Of Peroxisome Biosynthesis Genes FvPEX7 And FvPEX20 In Fusarium Verticillioides

Fusarium verticillioides is a major pathogen of maize and sugarcane,that causes ear rot and pokkah boeng disease respectively,which seriously affects their yield and quality.In addition,F.verticillioides accumulates a large amount of FB1 mycotoxins on the cereal,causing great harm to human and animal health.Peroxisome is an organelle with single membrane in eukaryotic cells and contains more than 50 enzymes involved in various physiological and metabolic pathways related to pathogenicity and secondary metabolite synthesis in the ascomycete.The peroxisomal matrix proteins containing peroxisomal targeting signal(PTS)type1(PTS1)or type 2(PTS2)are synthesized in the cytosol and then imported into peroxisomes by their respective receptors.In F.verticillioides,it is known that PTS2-containing matrix proteins are recognized by the receptor FvPex7 and co-receptor FvPex20,however their intrinsic roles in pathogenic process and FB1 biosynthesis remain elusive.Therefore,in this study we mainly explored the regulatory role of FvPex7 and FvPex20 in F.verticillioides pathogenicity and FB1 biosynthesis as well as the relationship between them.Firstly,we generated the single mutants and double mutant of FvPEX7 and FvPEX20 genes in Fv7600 wild type strain by homologous recombination method and analyzed their contribution to pathogenicity,FB1 biosynthesis and sporulation of F.verticillioides.Results obtained showed that pathogenicity,FB1 biosynthesis and sporulation were not only decreased in(35)Fvpex7 and(35)Fvpex20 single deletion mutants but also in(35)Fvpex7pex20 double deletion mutant.In addition,both the(35)Fvpex7 and(35)Fvpex7pex20 mutants grew slowly on minimum medium and showed reduced sensitivity to 200 μg/m L CR and CFW stress,while(35)Fvpex20exhibited a decreased sensitivity to 0.01% SDS stress compared to the wild type strain.Through subcellular localization,we confirmed that the localization of PTS2-containing proteins were altered in(35)Fvpex7 and(35)Fvpex20deletion mutants.Both FvPex7 and FvPex20 are localized in peroxisome and cytosol in mycelia,and they were completely colocalized in peroxisomes.But deletion of FvPEX20 resulted in a mislocalization of FvPex7 in peroxisome.Furthermore,we found that FvPex7 directly interacts with FvPex20 and the two PTS2-containing proteins interacted with FvPex7 by yeast two-hybrid.Taken together,F.verticillioides PTS2-containing proteins receptor FvPex7 and co-receptor FvPex20 contribute to pathogenicity and FB1 biosynthesis by affecting different metabolic pathways.The localization of FvPex7 on the peroxisomes is dependent on FvPex20,and FvPex7 cooperates with FvPex20 to regulate the transport pathway of PTS2-containing proteins.