Function Of Phosphoglucose Isomerase And Phosphomannose Isomerase In Aspergillus Flavus

Aspergillus flavus is a widely distributed pathogenic fungus capable of contaminating many economic crops such as peanut,maize,and so on,and producing highly toxic and carcinogenic aflatoxins,thus leading to extremely severe food safety problems and huge economic losses.Meanwhile,A.flavus is the second fungal pathogen causing aspergillosis in immunocomprised populations,which also poses a great threat to human health.Therefore,it is of great significance to control the infection and contamination caused by A.flavus.Cell wall is an important target for the devolopment of anti-fungal drugs.Key enzymes involved cell wall biosynthesis pathway are indispensable for maintaining cell wall integrity.Among them,phosphoglucose isomerase(Pgi)and phosphomannose isomerase(Pmi)play key roles in glucose metabolism and cell wall precursor synthesis pathways.However,their significances in growth and pathogenecity of A.flavus remain unknown.To investigate the contributions of Pgi and Pmi to growth and pathogenecity of A.flavus,deletion mutants and revertants of pgi and pmi genes were constructed by homologous recombination.Our results showed that both Pgi and Pmi were essential for the growth and development of A.flavus.TheΔpgi and Δpmi mutants required exogenous fructose or mannose to restore growth,respectively.Under the optimal condition both mutants exhibited significantly reduced sporulation,retarded sclerotial production,and sensitivity to hyperosmotic,oxidative and cell wall stresses as compared to the wild-type and revertant strains,indicating cell wall integrity is disrupted in both mutants.We also found that the Δpgi mutant strain showed severely retarded spore germination and sensitivity to low temperature,while the Δpmi mutant showed significantly retarded growth on solid medium and abnormal polarity growth of hyphae in liquid culture.These results indicate that the influences of Pgi and Pmi on A.flavus are different.The virulence of Δpgi and Δpmi mutant strains was significantly decreased in animal models of Caenorhabditis elegans and Galleria mellonella as well as in peanut and maize seed infection tests.In summary,this study revealed that both Pgi and Pmi are involved in regulation of growth and development,carbon metabolism,stress responses and pathogenicity of A.flavus.Our results indicate that Pgi and Pmi are important for growth and pathogenicity of A.flavus,thus they can be promising new targets for prevention and control of A.flavus infection and contamination.