球孢白僵菌光诱导抑菌次生代谢物BbABMs的生物合成与调控机制

Some secondary metabolites produced by entomopathogenic fungi possess the immunesuppressive, insecticidal and antimicrobial activities, and play important roles during fungal pathogenesis. Therefore, it’s important to study the biosynthesis pathway and regulation mechanism of these secondary metabolites. Our previous study showed Beauveria bassiana can produce a kind of yellow secondary metabolites with antibacterial activity under light stimulation (including three fractions, named BbABMs). A mutant which cannot produce BbABMs under the same conditions was screened from a T-DNA insertion mutant library. The random insertion site was mapped to a gene that displayed homology to a blue light receptor protein (white collar-1, Bbwc-1). This gene was disrupted by homologous recombinant and confirmed to regulate the production of BbABMs. In the present study, we will try to elucidate the chemical structures and biological activities of BbABMs, and isolate the genes involved in its biosynthesis using transcriptomic and biological information techniques. Furthermore, we plan to verify whether Bbwc-1 regulates the production of BbABMs by interaction with VelB/VeA/LaeA or CSN complexes using yeast two-hybrid and gene knockout methods. After finished this study, we expect to elucidate the structures and biological activities of BbABMs and clarify the regulation mechanism of Bbwc-1 on the production of BbABMs.

虫生真菌产生的部分次生代谢物具有抑制宿主免疫反应、毒杀昆虫或抑菌功能。因此，从基因水平上研究它们的生物合成及调控机制具有重要的理论和实践意义。课题组前期研究显示，球孢白僵菌在光照条件下会产生一类具有抑菌活性的黄色次生代谢物（命名为BbABMs），其分子量及理化性质不同于目前已知的球孢白僵菌次生代谢物。进一步筛选获得BbABMs合成消失的T-DNA插入突变体，并通过基因克隆及敲除实验证实，蓝光受体（Bbwc-1）调控BbABMs的产生。在此基础上，本研究拟首先解析BbABMs的化学结构，并利用比较表达谱及基因敲除等手段分析其生物合成途径；利用酵母双杂交及常规分子生物学手段分析Bbwc1是否通过LaeA或CSN复合体调节该类次生代谢物的合成。项目的完成有望弄清BbABMs的生物合成途径及调控机理，其研究结果对深入了解虫生真菌次生代谢产物的作用及其利用有重要意义。

虫生真菌产生的部分次生代谢物具有抑制宿主免疫反应、毒杀昆虫或抗逆功能。因此，从基因水平上研究它们的生物合成及调控机制具有重要的理论和实践意义。课题组前期研究显示，球孢白僵菌在光照条件下会产生一类黄色次生代谢物（命名为BbABM），其分子量及理化性质不同于目前已知的球孢白僵菌次生代谢物。本项目确定了BbABM的合成受光照诱导，并对该化合物进行了纯化及初步的结构鉴定。利用比较表达谱及基因敲除等手段，确定该化合物的生物合成途径受蓝光受体蛋白White Collar（WC）和受光照影响的全局性转录因子LaeA的调控。活性分析发现，BbABM在分生孢子在抗紫外过程中起到重要作用。同时通过转录组分析及RT-PCR筛选到部分可能参与BbABM合成的基因簇，经基因敲除，最终确定一个聚酮合酶基因为合成BbABM的核心基因。这些研究发现对深入了解虫生真菌次生代谢产物的作用及其利用有重要意义。