白念珠菌CaPPEl的克隆及其在酿酒酵母形态发生中的功能研究

CLONING AND FUNCTIONAL STUDY OF CaPPEl IN CANDIDA ALBICANS BY USING SACCHAROMYSES CEREVISIAE MODEL SYSTEM

白念珠菌的致病性与其形态转变相关,白念珠菌的形态转换受各种外界信号和细胞内信号转导途径的调控。转录因子Flo8在酿酒酵母形态发生中起重要作用,我们将白念珠菌基因组文库导入flo8缺失株中,筛选能够校正flo8缺失株侵入生长缺陷的基因,分离得到一个与酿酒酵母蛋白磷酸酯酶甲基酯酶PPEl同源的基因,命名为CaPPEl。CaPPEl的基因编码区全长1083bp,推测编码一个361氨基酸的蛋白。在单倍体酿酒酵母中,CaPPEl基因的表达可以部分回复flo8缺失株的侵入生长缺陷,但是在MAPK途径缺失株中不能进行侵入生长。在双倍体酿酒酵母中,CaPPEl基因的表达可以部分激活MAPK途径成员缺失株的菌丝生长缺陷,但却只能在flo8缺失株中产生微弱的激活作用。结果表明CaPpel在酿酒酵母的假菌丝生长和侵入生长中参与的信号转导途径不同。

The dimorphic transition of yeast and hyphal forms is one of most determinants in Candida albicans for its pathogenicity. This transition is regulated by several signal transduction pathways. Transcriptional factor Flo8 plays an important role in morphogenesis of Saccharomyces cerevisiae. In this work, a C. albicans genomic DNA library was introduced into a S. cerevisiae flo8/flo8 mutant and genes which could suppress invasive growth defect were isolated. A novel gene was isolated and designated CaPPE1 (Candida albicans PPE1 gene). CaPPE1 encoded for a 361 amino acid protein CaPpel, shared highest similarity in amino acids (35% identity) with the protein phosphatase methylesterase Ppel of S. cerevisiae. In haploid of S. cerevisiae, ectopic ex- pressed CaPPE1 could partially suppress the invasive growth defect of the flo8 mutant but failed to suppressed the invasive growth defects of the mutants in MAPK pathway(ste12/ste12 and tec1/ tec1). Ectopic expression of the CaPPE1 in diploid of S. cerevisiae suppress the filamentous growth defect of some mutants in MAPK pathway, but not in flo8/flo8 mutant under nitrogen starvation condition. It is suggested that CaPpel may be involved in different regulating pathways in diploid filamentous growth and in haploid invasive growth.