探討剔除白色念珠菌CaHGT6、CaORF19.7566、CaCDR4 和CaCDR3CDR4對白色念珠菌型態變化和生長情況之影響

Abstract

白色念珠菌(Candida albicans)是一種伺機性的病源真菌，通常會共生於人體當中，但是當宿主的免疫功能低下時，白色念珠菌就會開始增生並引起局部性或系統性的感染。白色念珠菌可以在酵母菌型和菌絲型之間轉換，而目前知道這型態之間的轉換是受到轉錄因子CaEfg1p和/或CaCph1p所調控。若將CaCph1和CaEfg1進行剔除後，白色念珠菌將會失去形成菌絲的能力而維持酵母菌型，並對於小鼠的毒性和致病力大幅下降。這表示白色念珠菌的型態轉變對於致病機制相當重要。 在比較CaEfg1p和/或CaCph1p基因表達模式，挑選表現量有差異的基因後，本研究中挑選的三個基因CaHGT6、CaORF19.7566和CaCDR4是表現量有差異的基因，而這些基因可能和菌絲生長或致病力有所關聯。又因這三個基因可能為轉運蛋白，因此本研究亦測定生長情況。藉由利用SAT1 flipper cassette 建構出三基因的雙套剔除株，並進行型態變化和生長曲線的測試。在結果中，型態相關的芽管生成、菌絲生成和侵犯力實驗，三個基因的雙套剔除株和野生株並無明顯差異，而在生長相關的測定中，三個基因的雙套剔除株和野生株也並無明顯差異。

Candida albicans is an opportunistic fungal pathogen, usually as a commensal in humans. However, when the host becomes immunocompromised, it may cause superficial and systemic infections. Candida albicans can switch from a yeast form into filamentous forms. It is known that the morphological transition is regulated by the transcription factors CaEfg1p and/or CaCph1p. The cph1/cph1 efg1/efg1 double mutant is defective in filamentous growth, locked in the yeast form, and became avirulent in a mouse model. This indicates that virulence is related to the morphogenesis in Candida albicans. The expressions of CaHGT6, CaORF19.7566 and CaCDR4 were affected by transcriptional factors CaEfg1p and/or CaCph1p in Candida albicans based on the result of expression profile comparison. These three genes may be related to hyphae growth or virulence, and they are putative transporter genes. In this study, I used SAT 1 flipper cassette to construct homozygous knock-out strains of these three genes and determined the effect on morphogenesis and their growth rates. In conclusion, there is no significant difference between the homozygous strain and the wild-type strain in their morphogenesis ability under the tested condition. And there is no difference between the homozygous strain and the wild-type strain in their growth rates under the tested condition.