建構 SAT1 質體之 polylinker 以及探討 CaPTR3 對白色念珠菌型態變化之影響

Abstract

白色念珠菌(Candida albicans)是一種伺機性的二倍體病原真菌，通常共生於 人體中，但是當宿主免疫功能低下時，白色念珠菌就會增生並引起局部性或系統 性的感染，嚴重時甚至造成宿主死亡。白色念珠菌具有型態之間轉換的能力，在 先前的研究中確定的有三種型態，分別為酵母菌型、假菌絲型、菌絲型。目前研 究指出型態之間的轉換受到轉錄因子 CaEfg1p 及 CaCph1p 正向調控，以及 CaTup1p 負向調控。將 CaCph1 和 CaEfg1 進行剔除後，白色念珠菌將會失去 形成菌絲的能力，只能維持酵母菌型態，且致病力與毒性明顯降低，這表示白色 念珠菌的型態轉變對於致病能力有重要關聯。白色念珠菌可將蛋白質降解成為多 肽鏈並吸收含氮的養分以利生長。當環境中只有蛋白質能作為氮來源時，白色念 珠菌會分泌天冬胺酸蛋白酶(secreted aspartic proteinases)將蛋白質降解成多肽鏈 加以吸收，並經由特定的胜肽轉運載體吸收至細胞內，其中 CaPTR2 和 CaPTR22 已被研究出是表現胜肽轉運載體的基因，而 PTR 家族中的 CaPTR3 仍屬未知。 在現有研究中，被認為其表現蛋白相似於酵母菌的 Ptr3p，在酵母菌的功能是一 個外部胺基酸的感應器。而在本實驗室先前的研究中，確定 CaPTR3 雙套基因剔 除株，對部分型態及性狀確實造成影響。本研究先建構 SAT1 flipper cassette 的 Polylinker ，再藉由新增的酵切位去建構 Captr3 單套基因回復株，確認新增 Polylinker 的可行性外，也同時確認 Captr3 在部分型態及性狀上造成的影響。研 究結果顯示，Captr3 在特定條件下，確實影響了菌落生成型態及菌落侵犯力，雙 套基因剔除株性狀較類似於 HLC54K。但是調控機制和其與含氮營養源運輸上的 功能性，需要更進一步實驗去證實。

Candida albicans is a common diploid and opportunistic fungus in human. When the host immunity is declining, it can cause focal or systemic infections, even death, especially in immunocompromised patients. The transcription factors CaCph1p 、 CaEfg1p and CaTup1p regulate the ability to change forms. Candida albicans can change between yeast and hyphal forms, and it had been known to correlate with pathogenicity. When proteins are sole source of nitrogen in environment, Candida albicans can digest proteins by secreted aspartic proteinases (Saps) to digest host proteins for cells. The specific protein known as peptide transporter is essential in this progress. PTR family is known to affect the up-take of peptides in Candida albicans. CaPTR2 and CaPTR22 have been suggested as peptide transporters, but the function of CaPTR3 is unknown. It is believed that CaPTR3 is similar to Ptr3p in yeast, recognized as a sensor for amino acids. In the lab, the Captr3/Captr3 null mutant strain is influential with invasion test and colony morphology in the previous study. Therefore, in this study, I first construct the polylinkers of SAT1 flipper cassette. And then I use the new multiple cloning sites to construct the CaPTR3 rescued strain, confirming the feasibility of the new polylinkers and the morphological change of CaPTR3 mutant. The result showed that CaPTR3 really affected the morphologenesis in a particular condition. But the mechanism and pathway among CaPTR3、CaCPH1、CaEFG1 and CaTUP1 need further investigation.