| Aspergillus flavus,a saprophytic fungus with strong reproduction ability,is widely distributed in nature.Aflatoxins produced by A.flavus has strong toxicity,and is extremely harmful to human society.Among them,the most toxic aflatoxin B1(AFB1)has been classified as the first carcinogen substance.Therefore,it is of great significance to study the mechanism of AFB1 synthesis.In recent years,some studies on transcription factors have been reported,and it was found that these transcription factors played a important role in various fungi.However,it is unclear that whether the transcription factor AflSnt2 involves in the synthesis of aflatoxins and pathogenicity in Aspergillus spp..In this study,the bio-function of AflSnt2 in A.flavus was analyzed.This study identified aflsnt2 gene,which encodes AflSnt2 protein in A.flavus by bioinformatic analysis.In this study,aflsnt2 gene deletion(?aflsnt2)and complementary(?aflsnt2-C)strains were constructed by using the homologous recombination method,respectively.It was found in this study that AflSnt2 plays a key role in development,secondary metabolism and pathogenicity of A.flavus.The results of the study showed that the number of conidia produced by ?aflsnt2 strain on the PDA medium was significantly reduced compared with wild type(WT)and complementary strains,and the length of the conidiophore of ?aflsnt2 strain was significantly shorter,too.what's more,the absence of aflsnt2 gene blocked the sclerotia formation and the biosythesis of AFB1 in A.flavus.Above results indicated that AflSnt2 is a positive regulator in conidia production,sclerotial formation and aflatoxin biosynthesis of A.flavus.This study also explored the response of ?aflsnt2 strain to a variety of external stresses.The results showed that ?aflsnt2 strain was more sensitive to hydrogen peroxide and salt ions.It was found that?aflsnt2 strain could not grow when the medium supplemented with 7 mmol/L hydrogen peroxide,and that the growth of knockout strain was promoted in the environment with 1.2 mol/L Sorbitol.In addition,the growth rate of ?aflsnt2 strain also responded to the stimulation of the sodium dodecyl sulfate,a cell membrane inhibitor,which indicated that AflSnt2 is associated with cell membrane integrity in A.flavus.The,results of A.flavus infecting peanut and maize seeds showed that ?aflsnt2 strain produced distinctly less conidiophore and no AFB1 was detected from ?aflsnt2 strain compared with wild type and complementary strains,which were consistent with those previous results of this study.These results domenstrated that AflSnt2 plays a key role in aflatoxin B1 biosynthesis and the pathogenicity of A.flavus to crops.According to the related reports,fungal infection process might link to the changes of hydrolase activity,this study further investigated the effect of AflSnt2 to the activity of amylase and lipase in A.flavus,the results suggested that the activity of amylase and lipase activity in aflsnt2 gene knockout strain was obviously declined compared to wild type and complemented strains,which revealed that AflSnt2 affects the pathogenicity of A.flavus to plant seeds,at least partly,by regulating the activity of hydrolases.In conclusion,transcriptional factor AflSnt2 in A.flavus,was preliminary identified in this study.The results showed that AflSnt2 involves in regulation of a variety of biological processes in A.flavus,such as mycelial growth,conidia production,sclerotia formation,secondary metabolism,environmental stresses response and pathogenicity. |
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