球毛壳菌沉默基因激活与新农药先导化合物发现

Today’s challenges of weed and pest resistance and the invention of selective, environmentally benign, low use rate, and cost-effective active ingredients promote the developments in the design and synthesis of agrochemicals. The agrochemicals from nature have successfully been introduced to the market to control insect pests, plant diseases and weeds, and will still meet the demands of both ecological environment and sustained development. Therefore, the method to discover new agrochemicals and their leads from nature is still an efficient way in the future. Microbial genomics has revealed that many microorganisms have far greater potential to produce specialized metabolites than has been discovered by classic screening-based methods. Inducing the production of metabolites that are not expressed under conventional laboratory culture conditions is a novel way to find new natural products. Based on previous study and under the guidance of bioassays, we will be able to isolate about twenty compounds by activating silent genes in Chaetomium globosum. Using precursor-directed biosynthesis, a collection of bioactive metabolites will be obtained, which could be leading compounds for novel and safe pesticides.

低剂量高防效的需求以及有害生物抗药性的发展，促进了新农药研发的不断创新。从天然产物中筛选农药活性先导化合物是新农药创制的重要途径。然而，在常规培养条件下，大多数生物合成基因簇不表达或表达很低（被称为沉默基因），导致大量已知化合物被重复发现。已有文献表明，在沉默的基因簇里，可能蕴藏着大量能够编码产新颖次生代谢产物的酶基因。激活沉默基因并从中寻找新的天然活性分子，是发现先导化合物的新策略。本项目在前期基础上，拟对一株银杏内生真菌Chaetomium globosum CDW7进行研究，通过化学诱导的办法，激活沉默基因，在活性导向下分离目标产物，并用前体定向生物合成技术定点修饰活性产物，有望发现新活性化合物15-20个，新骨架类型2-3个，进而为新型、高效、安全的农药先导化合物的研究与利用提供源头性成果。

利用激活沉默基因的方法并结合生物转化，从银杏内生真菌Chaetomium globosum CDW7的发酵产物中分离得到化合物23个，其中新化合物17个，新骨架类型3种。Chaetoviridin A（18）具有良好的抑菌活性，在200 μg/mL浓度下对油菜菌核病防效为64.3%，与阳性对照多菌灵相当；chaetoindolone A（12）在200 μg/mL浓度下，对水稻白叶枯病的防治效果达到81.6%，与阳性对照硫酸链霉素相当。利用同位素标记实验，对新骨架化合物的生物合成途径进行了初探。上述结果表明，球毛壳菌可以产生结构新颖的活性分子，而沉默基因激活技术可以充分激发微生物产生新活性分子的潜能，为新先导结构的发现提供新的思路。本项目已发表SCI论文6篇（标注资助），进展顺利，完成了预期研究计划。