Preliminary Study On Function Analysis Of The G Protein A Subunit GpaB In Aspergillus Flavus

Aspergillus flavus is one of the most important opportunistic pathogens of crops and animals.The carcinogenic mycotoxin,aflatoxins produced by this pathogen cause a health problem to human and animals.The G protein signaling pathway is a transmembrane signaling pathway which is prevalent in eukaryotic organisms.The literatures confirmed that the signaling pathway can be induced in response to different stimulation of many extracellular signals.The G protein signaling pathway plays an important role in the regulation of the growth,reproduction,pathogenicity and the synthesis of secondary metabolites of filamentous fungi.Based on the preliminary study on the protein subunit GpaB?AFLA₀18540?of Aspergillus flavus,we found that this gene had different effects on the growth,sporulation,sclerotium,pathogenicity,aflatoxins biosynthesis and stress resistance of Aspergillus flavus.The gene knockout mutant AgpaB and the complementary strain?gpaB-C were constructed by homologous recombination.In the experiment,it was found that the mutant of Aspergillus flavus lacking gpaB gene had no effect on the growth of Aspergillus flavus compared with wild type.The sporulation rate and toxin production were seriously reduced,which sclerotia was increase.Furthermore,we found that the expression levels of conidiation-related genes abaA and brlA,aflatoxin-related genes aflR,aflS and aflP in AgpaB were significantly lower than wild-type.And the expression levels of sclerotium-related genes nscC,nscD and sclR were higher than that of wild type.The inhibitory rates of AgpaB in colony growth and oxidative stress experiments were significantly higher than that of wild type by stimulation of the external environment,indicating that the gpaB gene was necessary for sensing and responding to cell wall integrity and oxidative stress of Aspergillus flavus.In this study,we investigated the effects of G protein a subunit GpaB on the growth,sporulation,fecundity,toxin production and pathogenicity of Aspergillus flavus,and found that they were also involved in response to external environmental stimuli.This study provides a basis for further exploration of the mechanism of production of aflatoxins,and also provides a new idea and theoretical support for the prevention and control of Aspergillus flavus.