南极海洋真菌(Tilletiopsis sp. ICE-01)DMSP降解新机制及其极端环境降解特性

海洋微生物降解DMSP产DMS是海洋硫循环的重要过程。目前该过程研究主要聚焦于细菌，真菌研究较为匮乏，仅发现子囊菌具有该功能，南极海洋真菌尚未有报道。本项目前期筛选到高效降解DMSP产DMS的南极海洋腥掷孢菌，属于外担菌纲的新降解菌种。基于全基因组数据分析，发现该菌株具有不同于目前已知真菌DddP降解途径的DddD降解途径。本项目将根据推定的降解途径，通过基因克隆表达与重组工程菌构建等，获得降解基因与降解酶，解析其结构特征与功能特性；通过基因突变等方法研究降解酶构效关系，通过同位素示踪技术确定降解产物，探明腥掷孢菌的DMSP降解途径；在此基础上，利用qRT-PCR、Western Blot与转录组测序等技术，了解腥掷孢菌在极端环境中的降解特性与降解分子机制。本项目有助于发现更多DMSP降解生物种类及降解特性，探明南极真菌DMSP降解新机制，可望深入了解南极真菌在海洋硫循环过程中的重要作用。

Marine microorganisms are the primary mediators of dimethylsulfoniopropionate (DMSP) cleaving into dimethyl sulfide (DMS), which is an important process of marine sulfur cycling. Many different types of marine bacteria are known to make DMS from DMSP, whereas marine fungi reported relatively scarcely. DMSP cleavage only occurs in some Ascomycete fungi. Besides, the DMSP cleavage pathways and mechanisms of Antarctic fungi have not been reported. Here we have isolated an Exobasidiomycete fungus, Tilletiopsis sp. ICE-01, obtained from the Antarctica, which can highly efficient cleave DMSP into DMS. According to the genome sequence analysis, we speculate that this Antarctic Tilletiopsis has a DMSP cleavage pathway contained DddD lyases, which differs from that in all known fungi mediated by DddP lyases. This project will identify the structure and function of the gene and protein of DMSP cleavage enzyme by gene cloning, expression and recombinant stain construction. Using gene mutants and isotope tracer, we will detect the structure activity relationship of DMSP cleavage lyases and identify labelled catabolic products, accordingly the DMSP cleavage pathways of Tilletiopsis sp. ICE-01 will be clarified. Then, the expression levels of gene and protein in response to different extreme environments are determined to elucidate the characteristics and molecular mechanisms of DMSP cleavage of Tilletiopsis sp. ICE-01 in the Antarctic extreme environments using qRT-PCR, Western Blot, and transcriptome analysis. The results of this study may help to find more biological species and characteristics of DMSP degradtion and discover novel DMSP degrading mechanisms of Antarctic marine fungi. They make us better understand the important role of the Antarctic fungi in marine sulfur cycling.