Application of atoxigenic strains to compete against toxigenic strains of Aspergillus flavus strains has emerged as one of the practical strategies for reducing aflatoxin contamination in corn, peanut, and tree nuts. The actual mechanism that results in aflatoxin reduction is not fully understood. Real-time RT-PCR and relative quantification of gene expression protocol were applied to elucidate the molecular mechanism. Transcriptional analyses of aflatoxin biosynthetic gene cluster in dual culture of toxigenic and atoxigenic A. flavus strains were carried out. Six targeted genes, aflR, aflJ, omtA, ordA, pksA, and vbs, were downregulated to variable levels depending on paired strains of toxigenic and atoxigenic A. flavus. Consistent with the decreased gene expression levels, the aflatoxin concentrations in dual cultures were reduced significantly in comparison with toxigenic cultures. Fluorescent images showed fungal hyphae in dual culture displayed green fluorescent, and contacts of live hyphae were seen. A coconut agar plate assay was used to show that toxigenic A. flavus colony produced blue fluorescence under long UV exposure, suggesting that aflatoxin is exported outside fungal hyphae. Furthermore, the assay was applied to demonstrate the potential role of thigmo-regulation in fungal interaction.

中文翻译：

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黄曲霉的产毒和产毒菌株的双重培养可深入了解黄曲霉毒素的生物合成抑制和真菌相互作用。

作为减少玉米，花生和坚果中黄曲霉毒素污染的实用策略之一，应用抗毒素菌株与黄曲霉菌株的抗毒素菌株竞争已成为现实。导致黄曲霉毒素减少的实际机制尚不完全清楚。应用实时RT-PCR和基因表达方案的相对定量来阐明其分子机制。进行了产毒和产毒黄曲霉菌株双重培养中黄曲霉毒素生物合成基因簇的转录分析。六个靶向基因aflR，aflJ，omtA，ordA，pksA和vbs，被下调到可变水平，取决于成对毒力和产毒黄曲霉成对菌株。与降低的基因表达水平一致，双重培养物中的黄曲霉毒素浓度与产毒培养物相比明显降低。荧光图像显示双重培养中的真菌菌丝显示绿色荧光，并观察到活菌丝的接触。使用椰子琼脂平板测定法显示，在长时间的紫外线照射下，产毒黄曲霉菌落产生蓝色荧光，这表明黄曲霉毒素出口到真菌菌丝之外。此外，该测定法被用于证明硫胺素调节在真菌相互作用中的潜在作用。