Functional Analysis Of Peroxisomal Targeting Signal Receptor Gene In Aspergillus Flavus

Aspergillus flavus is a widely distributed soil saprophytic fungus which causes diseases both in humans and animals,as well as infect food and oil crops,leading to economic losses.A.flavus produces aflatoxin,a strong toxic and carcinogenic substance,which is harmful to human health.Peroxisome,an organelle with a monolayer membrane,participates in many important physiological metabolisms in eukaryotes.It is known that more than 30 proteins are involved in the formation and development offungal peroxisomes.These proteins,encoded by the Pex gene,are named Peroxins.The function of most Peroxins is related to the transport of matrix proteins from the cytoplasm to peroxisomes,where Pex5 and Pex7 are receptors for peroxisomal targeting signal PTS1 and PTS2,respectively.Although studies have been conducted on the biological function of peroxisomes in filamentous fungi,the study of the A.flavus Pex gene has not been reported.In this study,AflPex5 gene knockout mutant strain(?Af1Pex5)andcomplementation strain(?AfJPex5-com)were constructed to investigate the biological functions of AflPex5 in A.flavus.Fluorescent localization analysis revealed that the transportation of PTS1-containing matrix proteins into peroxisomes was completely blocked in the ?AflPex5 mutant.?AflPex5 mutant also showed a variety of phenotypic defects when compared with wild-type(WT)and ?AflPex5-com.?AflPex5 mutant had a slower growth rate,and a significantly reduced production of conidia and sclerotia.The ability of AAflPex5 mutant to utilize fatty acids was reduced,especially with respect to long-chain fatty acids.The integrity of its cell wall was undermined,and its tolerance to oxidative agents was impaired.In addition,?AflPex5 mutant displayed an increased accumulation of reactive oxygen species in the hyphae.The synthesis of aflatoxin and cyclopiazonic acid by ?AflPex5 mutant was significantly decreased.?AflPex5 mutant showed a deficiency in the infection of peanut and maize seeds,as the production of conidia and aflatoxin on the seeds were significantly reduced.In summary,?flPex5 gene plays a vital role in the transportation of peroxisomal matrix protein into peroxisomes,fungal development,mycotoxin synthesis and pathogenicity of A.flavus.This study provides a theoretical basis for revealing the mechanism of development,aflatoxin synthesis and pathogenicity to crops in A.flavus.This study will be conducive to explore comprehensive prevention methods and new agents to reduce aflatoxin contamination.