Preliminary Study On Molecular Mechanism Of Aflatoxigenic Aspergillus Flavus Response To Temperature

Aspergillus flavus is the main fungus producing aflatoxin.Eating food or products contaminated with aflatoxin can cause damage to the liver,kidneys,and nervous system,and can cause immunosuppression and carcinogenesis,and even death.Temperature is a key factor affecting the synthesis of aflatoxins.Although several fungal toxicity-related regulatory pathways have been reported,the regulation of aflatoxin synthesis and mycelial growth is still unclear at different temperatures.Therefore,revealing the molecular mechanism of temperature affecting aflatoxin synthesis is of great significance for effective prevention and control of A.flavus.In this study,the differentially expressed genes(DEGs)and regulatory pathways of A.flavus at different temperatures were analyzed by the RNA-Seq.The results showed that a total of 1,870 and 728 DEGs were identified at 20? and 37? fungal mycelia compared with that of control(28?),respectively.Majority of the DEGs at 37? sample belonged up-regulated genes,while majority of the DEGs at 20? sample belonged down-regulated genes.Majority of the enriched pathways of DEGs by lower temperature were quite different compared to that of the higher temperature,only small portion of the pathways were shared by different temperatures.Small GTPase mediated signal transduction and calcium:proton antiporter activity pathways were affected by lower temperature,while no signal related pathways were enriched by higher temperature.Hydroquinone:oxygen oxidoreductase activity was only enriched in the DEGs impacted by higher temperature.The fungal growth rates and aflatoxin production abilities were also different under different temperatures.The facts suggest that aflatoxin biosynthesis and fungal growth of A.flavus under different temperatures should be regulated by different pathways.GPCR plays an important regulatory role in the growth and development of fungi.Due to the differential expression of gprC,gprD and gprG under different temperatures,three deletion mutants of AgprC,?gprD and AgprG were constructed in this experiment,and their toxicity at different temperatures was detected.The results showed that AgprC and AgprG had no significant difference in the amount of toxin produced compared with the wild type,while the AgprD mutant had a three-fold increase in toxin production compared to the wild type at 20?.Those results will provide evidence for the in-depth study of the regulation of the growth and production of A.flavus under the influence of temperature.