活性氧介导磁场对红曲色素和桔霉素合成的双向调控机制

Citrinin contamination severely limits the the use of Monascus pigments. In our previous work, we found that magnetic fields can significantly increase pigments together with decline dramatically of production of citrinin, and showed that magnetic fields significantly induced the expression of genes of pigment biosynthesis came with depressing the expression of genes of citrinin biosynthesis, and accompanied with differently expressed genes of antioxidants and transcription factors(reactive oxygen species control system). These results indicated that magnetic fields mediateed by reactive oxygen species played an influential role to biosynthesis of pigments and citrinin, but the exact mechanism remains unclear. On the basis of our previous work，this current project will fully disclose the bidirectional regulation mechanism of magnetic fields mediated by reactive oxygen species to biosynthesis of pigments and citrinin by controlling ROS through magnetic fields combined gene knockout and gene over-expression from phenotype, transcription, enzyme activity and metabolite level. Research achievements in this research project will provide universal theoretical reference and technical support for improving production strains of safe and high-yield pigments, and for the application of magnetic fields in regulation for secondary metabolites in other filamentous fungi.

桔霉素污染严重限制了红曲色素的广泛应用。本课题组采用磁场辅助发酵技术实现了安全型红曲色素的生产，发现磁场处理能显著提高色素合成基因表达的同时，明显降低桔霉素合成基因的表达，并诱导抗氧化蛋白、调控次生代谢和氧化胁迫的偶联转录因子（活性氧控制系统）的显著表达。这些研究表明：活性氧介导磁场对红曲色素和桔霉素合成有双向调控作用。然而，活性氧介导磁场是如何实现这种双向调控作用的？针对这一问题，本研究拟采用磁场处理与基因敲除和过表达技术相结合，控制胞内活性氧水平，从表型、基因转录、酶活、代谢物等水平，解析磁场、色素和桔霉素合成和抗氧化系统之间的作用关系，阐明活性氧介导磁场对色素和桔霉素合成的双向调控机制。研究成果将为合理高效开发安全型高色价红曲色素生产菌奠定理论指导，并为磁场在调控其他丝状真菌次生代谢物合成应用提供技术支持。

红曲色素是中国特色食用微生物红曲菌的主要次生代谢物，广泛用于食品工业。但桔霉素污染严重限制了红曲色素的广泛应用。本课题组采用磁场辅助发酵技术实现了安全型红曲色素的生产，既能提高色素合成基因表达，又明显降低桔霉素合成基因的表达，并诱导抗氧化蛋白和偶联转录因子的显著表达。表明活性氧（ROS）介导磁场对红曲色素和桔霉素合成具有双向调控作用。然而内在的机制尚不清楚。本项目构建了抗氧化酶基因的缺失突变体，改变红曲菌胞内的活性氧水平，发现突变体的胞内ROS水平增高，色素产量提高，桔霉素合成降低；而且磁场和氧化剂胁迫对代谢物合成具有协同效应，证实了分化期高水平的ROS是磁场双向调控红曲色素和桔霉素合成的重要指标。磁场处理结合qPCR、酶活测定和转录组测序，比较了突变体和野生菌在表型、基因转录、酶活、代谢物等水平的差异，发现突变体在分化期胞内的ROS水平较高，抗氧化基因的转录水平下调，色素合成关键基因转录水平上调，桔霉素合成关键基因的转录水平下调，转录因子转录水平双向表达，共同导致磁场对红曲色素和桔霉素合成的双向调控。研究成果将为合理高效开发安全型高色价红曲色素生产菌奠定理论指导和技术支持。