利用多體學探討藥用蟲生真菌之蟲草素生合成路徑

Abstract

蟲草素(cordyepin)屬腺苷異構物，於1950年初次自北蟲草分離，並被視為北蟲草中可抑制癌細胞生長之主要化合物。蟲草素之生合成雖已被報導與抑制腺苷脫氨酶之化合物噴司它丁有關，然而其上游代謝路徑仍有待進一步探討。此外，蛇形蟲草屬(Ophiocordycipitaceae)，包含西藏蟲草及臺灣蟲草之蟲草素生合成路徑，因基因差異性，目前依然未知。本研究選出五種不同生長階段之北蟲草，包含固態菌絲體、菌液、與米基上初步轉色之菌絲體、發育中及老化之子實體，結合轉錄體及代謝體學探討蟲草素生合成在生長過程中之分子機制，並發現精氨酸(arginine)在其中扮演重要角色。我們也發現北蟲草菌絲體在經過近紅外光處理後能顯著提升蟲草素產量，並同樣進行了轉錄體分析，更再次驗證精氨酸對於蟲草素生成之重要性。同時，本研究將先前利用次世代定序完成的臺灣蟲草全基因序列針對北蟲草中存在已知的蟲草素生合成相關基因進行比對，發現僅存在一段與北蟲草中cns4相似之片段。另一方面同步進行長片段定序技術(結合次世代定序及三代定序)，將臺灣蟲草再次進行長片段定序，提供更完善的全基因序列。本研究結合包含基因體學、轉錄體學及代謝體學之研究應用於探討蟲生真菌中蟲草素生合成路徑，為未來藥理功能開發及應用上建立完善基礎。

Cordycepin, an analogue of adenosine, is first isolated and identified from Cordyceps militaris in 1950 to be regarded as a bioactive compound in inhibiting cancer cell growth. Although the biogenic analysis of cordycepin was reported to couple with the adenosine deaminase inhibitor, pentostatin, in Cordyceps militaris, the upstream precursor during developmental stages still remains unclear. Besides, it remains a puzzle in Ophiocordycipitaceae (including Ophiocordyceps sinensis and Ophiocordyceps formosana) due to their genetic discrepancy. In this study, 5 different development stages, including mycelia in solid and suspension as well as pre-matured and aged fruiting bodies of Cordyceps militaris have been harvested for transcriptomics and metabolomics analyses. We found that arginine-related pathways were activated whenever cordycepin increased. Besides, near infrared spectrum was proved to be able to enriched cordycepin production, and proceeded the transcriptomics as well, further confirmed the importance of arginine. Meanwhile, we searched the published protein sequences related to cordycepin against the draft genome of O.formosana and revealed only one scaffold with high identity compare to cns4 in C.militaris. We conducted DNA whole genome sequencing against Ophiocordyceps formosana by combining nanopore sequencing and illumina sequencing, to get a better quality of whole genome sequence as well. Together, this study conducted multi-omic analysis to illuminate the biogenesis of cordycepin in these entomopathogenic Ascomycete fungi, which provides the foundation for the further novel pharmacologically potential discovery and application.