Function Analysis Of Peroxisome Genes FgPex2and FgPex3in Fusarium Graminearum

Fusarium head blight （FHB） is an important world-wide disease on wheat caused by Fusariumgraminearum sensu lato which occurred seriously in our country during recent years. FHB can lead tohuge yield loss and make the infected grains caintained trichothecene mycotoxins which is a seriousthreat to human and animal health. Peroxisomes are single-membrane-bound organelles that arerequired for diverse biochemical processes, including β-oxidation of fatty acids and detoxification ofreactive oxygen species （ROS）. Proteins that control peroxisome assembly, division and inheritance arenamed peroxins （encoded by PEX genes）. Dysfunction of peroxins causes fatal human peroxisomebiogenesis disorders and PEX genes also play an important role in fungus. A better understanding of thefunction of the PEX genes in F. graminearum will be helpful in parsing the pathogenesis and toxinsynthesis mechanism, exploring novel drugs against FHB, developing diseases comprehensive controlway and reducing the toxin contamination.We used reverse genetics strategy in this study. We investigated the biological functions of twoPEX genes FgPex2and FgPex3which are indicated played important roles in the peroxisomalmetabolism pathway in F. graminearum by target gene deletion and complementary strategy.1. Acquisition of gene deletion and complementary mutants.We identified PEX homologous genes FgPex2（FGSG₀0724） and FgPex3（FGSG₀6942） usinggenome comparison method. Then we finished the job of gene deletion and complementary vectorsconstruction and got the mutants which were detected by PCR and southern blot.2. The gene function analysis of FgPex2.Compared with wild type parent, FgPex2deletion mutant showed a slow growing rate, fewer aerialmycelia and conidiation. The deletion mutant showed increased sensitivity to osmotic stress mediatedby NaCl, KCl and decreased sensitivity to caffeine, H2O2,calcofluor white, carbendazim andtebuconazole. Deletion of the FgPex2blocked the protein matrix import with PTS1and PTS2signalpathways. The ability of using fatty acids reduced with the increasing of the carbon chain in the deletionmutant. The deletion mutant is almost completely unable to use long chain fatty acid. The deletionmutant had defects in perithecia and ascospore maturation. Pathogencity assays on tomato and wheathead showed that the mutant was unable to infect. ROS accumulation increased.3. The gene function analysis of FgPex3.Compared with wild type parent, FgPex3deletion mutant showed a slow growing rate, fewer aerialmycelia and conidiation, shorter spore length. The deletion mutant demonstrated increased sensitivity toSDS, caffeine, calcofluor white, congo red and osmotic stress mediated by KCl, sorbitol and alsoshowed decreased sensitivity to H2O2and tebuconazole. Deletion of the FgPex3blocked the proteinmatrix import with PTS1and PTS2signal pathways. The ability of using fatty acids reduced with theincreasing of the carbon chain in the deletion mutant. The deletion mutant was almost completelyunable to use long chain fatty acid. The deletion mutant had defects in perithecia and ascospore maturation. Pathogencity assays on tomato and wheat head showed that the mutant was unable to infect.ROS accumulation increased and survival ability decreased significantly.The results of our research showed that the genes FgPex2and FgPex3played fatal roles in myceliagrowth, pathogenicity, fatty acid oxidation, ROS metabolism, sexual reproduction and matrix proteintransport in F. graminearum.