利用表观遗传修饰激活海洋真菌中沉默次级代谢产物及其生物合成调控研究

Ocean, with its particular ecological environment, has nurtured versatile microbial resources; and it's the unexplored vital source of novel natural products. However, many microbial secondary metabolic pathways are silent under regular culture conditions; while these silent pathways could be induced or activated by epigenetic modifications, andhence improving the chemical diversity of their metabolites. Our previous study showed that the diterpenoids, isolated from the marine alga-derived endophytic fungus Aspergillus wentii EN-48, have relative strong cytotoxic activities against cancer cells; whereas the biosynthesis of these diterpenoids may need the light induction. A mangrove-derived endophytic fungus MA-143 was also isolated recently, it could produce diverse metabolites under different culture conditions. Based on previous studies, in this project we are interested to use the epigenetic modification strategies, like environmental stresses (heat shock, light or ethanol stress) and addition of inhibitors of enzymes (histone deacetylase and DNA methyltransferase), in the biological and chemical screenings, to fully explore the secondary metabolic biosynthetic capacity of the two strains. And then isolate and obtain new marine natural products with novel structures and strong bioactivities, which might provide candidate compounds for novel marine-derived drugs. For those potential novel compounds with application prospect (like diterpenoids), how their biosynthesis are induced and regulated by these epigenetic modifyers will be further investigated, which would provide scientific basis for the effective use of the marine natural products.

海洋特殊的生态环境蕴育了多样性的微生物资源，是未被充分发掘的新天然产物的重要来源。而在正常培养条件下，很多微生物次级代谢途径是沉默的；利用表观遗传修饰可诱导、激活其沉默代谢途径，增加其代谢产物的化学多样性。我们前期研究发现，海藻内生真菌温特曲霉EN-48中四降二萜有较强的细胞毒活性，而其生物合成需要光照诱导。近期又分离到红树林来源真菌MA-143，在不同培养条件下可产生多样性的代谢产物。本项目拟在已有工作基础上，通过环境胁迫(热激、光照、乙醇刺激)和添加酶抑制剂(组蛋白脱乙酰酶抑制剂和DNA甲基化转移酶抑制剂)等表观遗传修饰策略，进行生物活性和化学筛选，充分挖掘其次级代谢产物合成能力；分离获得新结构、强活性的新天然产物，为海洋创新药物研究提供候选先导化合物。对有前景的潜力化合物(如四降二萜)，进一步探讨表观遗传因素对其生物合成的诱导和调控机理，为海洋天然产物的有效利用提供科学依据。

海洋环境有丰富多样的微生物资源，是未被充分发掘的新天然产物的重要来源。利用表观遗传修饰可诱导激活沉默次级代谢途径，进而增加海洋真菌代谢产物的化学多样性。本课题在前期研究基础上，对构巢曲霉MA-143和温特曲霉EN-48等海洋来源真菌，通过改变培养条件或添加酶抑制剂等表观遗传修饰策略，分离获得了结构多样的新天然产物。从构巢曲霉中共分离鉴定21个化合物，其中11个新化合物，包括7个二氢喹啉酮类和4个喹诺唑啉酮类等；活性测试结果显示部分化合物有卤虫致死活性。从温特曲霉中分离鉴定12个蒽醌类化合物，其中4个新化合物，以及8个二萜类化合物。活性测试发现，蒽醌类化合物有较强的抗植物病原菌和自由基清除活性，而四降二萜类化合物具有较好的抗肿瘤活性。针对有应用前景的抗肿瘤四降二萜类化合物，进一步对温度、盐度、pH和发酵时间等条件进行了优化和表观遗传修饰，获得了静置规模发酵最佳条件参数，为抗肿瘤成药性评价和作用机理研究奠定了基础。