基因AFLA_105170调控黄曲霉生长及黄曲霉毒素B1合成的分子机制

    Molecular Mechanism of Transcription Factor AFLA_105170 Regulating Growth and Aflatoxin B1 Synthesis in Aspergillus flavus

    • 摘要: 黄曲霉毒素B1(AFB1)是黄曲霉产生的剧毒次级代谢产物,危害粮食安全和人体健康。为了探究O-甲基转移酶AFLA_105170基因在黄曲霉生长发育及AFB1合成方面的功能,构建了AFLA_105170基因缺失菌株,通过表性分析评估该基因缺失对黄曲霉生长发育和致病性的影响;利用色谱层析和高效液相色谱检测AFB1含量,分析该基因缺失对AFB1合成途径基因表达水平的影响;并通过胁迫试验及染色试验检测细胞壁、膜的完整性变化。结果表明:AFLA_105170基因缺失影响黄曲霉生长、产孢及菌核产生,严重抑制AFB1的生物合成;在PDB和PDA培养基中,AFB1含量分别下降69.81%和64.56%,与AFB1合成相关基因aflJaflWaflSaflM显著下调;该基因缺失破坏细胞壁、膜的完整性,降低黄曲霉在谷物中的侵染能力。综上所述,AFLA_105170基因在黄曲霉中具有重要功能,该基因缺失通过破坏壁、膜完整性抑制黄曲霉的生长;并通过抑制AFB1合成基因的表达水平,进而抑制AFB1的合成。

       

      Abstract: Aspergillus flavus can produce the highly toxic secondary metabolite aflatoxin B1 (AFB1), which poses a serious threat to food safety and human health. To investigate the effect of the transcription factor AFLA_105170 on A. flavus, this study successfully constructed a gene deletion strain of AFLA_105170 using a homologous recombination strategy. The effect of AFLA_105170 gene deletion on the growth phenotype and sclerotia formation of A. flavus was first determined. The effect of the AFLA_105170 gene deletion on AFB1 biosynthesis was examined using thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC). The effect of AFLA_105170 gene deletion on the expression levels of genes involved in AFB1 synthesis was further detected by fluorescence quantitative PCR (RT-PCR). The cell wall and membrane integrity of the AFLA_105170 mutant were examined by stress response and staining assay. Finally, the effect of AFLA_105170 gene deletion on the pathogenicity of strains was investigated using peanut and maize as media. The results showed that deletion of AFLA_105170 significantly inhibited the growth, spore development, sclerotia production, and AFB1 production. It was found that AFB1 yield in the AFLA_105170 gene deletion strain decreased by 69.81% in PDB medium and by 64.56% in PDA medium respectively. Furthermore, RT-PCR results showed that AFB1 synthesis-related genes, aflJ, aflW, aflS, and aflM were significantly down-regulated in AFLA_105170 deletion strain. Moreover, the integrity of cell membrane and cell wall in the AFLA_105170 gene deletion strain were disrupted, and its pathogenicity in peanut and maize was reduced. These results suggest that the deletion of AFLA_105170 inhibits A. flavus growth by damaging the integrity of the cell wall and membrane, and affects AFB1 biosynthesis by suppressing the expression of genes involved in the AFB1 synthesis. The results of the study provide a scientific basis for effective prevention and control of A. flavus and aflatoxin.

       

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