Nagahashi Shigehisa, Mio Toshiyuki, Ono Naomi, Yamada-Okabe Toshiko, Arisawa Mikio, Bussey Howard, Yamada-Okabe Hisafumi
Department of Mycology, Nippon Roche Research Center, 200 Kajiwara, Kamakura, Kanagawa 247, Japan.
Department of Biology, McGill University, 1205 Dr. Penfield, Montreal, Quebec, Canada H3A 1B1.
Microbiology (Reading). 1998 Feb;144 ( Pt 2):425-432. doi: 10.1099/00221287-144-2-425.
Recent studies have revealed that fungi possess a mechanism similar to bacterial two-component systems to respond to extracellular changes in osmolarity. In Saccharomyces cerevisiae, Sln1p contains both histidine kinase and receiver (response regulator) domains and acts as an osmosensor protein that regulates the downstream HOG1 MAP kinase cascade. SLN1 of Candida albicans was functionally cloned using an S. cerevisiae strain in which SLN1 expression was conditionally suppressed. Deletion analysis of the cloned gene demonstrated that the receiver domain of C. albicans Sln1p was not necessary to rescue SLN1-deficient S. cerevisiae strains. Unlike S. cerevisiae, a null mutation of C. albicans SLN1 was viable under regular and high osmotic conditions, but it caused a slight growth retardation at high osmolarity. Southern blotting with C. albicans SLN1 revealed the presence of related genes, one of which is highly homologous to the NIK1 gene of Neurospora crassa. Thus, C. albicans harbours both SLN1- and NIK1-type histidine kinases.
最近的研究表明，真菌拥有一种类似于细菌双组分系统的机制来响应细胞外渗透压的变化。在酿酒酵母中，Sln1p同时包含组氨酸激酶和感受器（应答调节子）结构域，并作为一种渗透压感受器蛋白，调节下游的HOG1丝裂原活化蛋白激酶级联反应。白色念珠菌的SLN1是利用一株条件性抑制SLN1表达的酿酒酵母菌株进行功能克隆得到的。对克隆基因的缺失分析表明，白色念珠菌Sln1p的感受器结构域对于拯救缺乏SLN1的酿酒酵母菌株并非必需。与酿酒酵母不同，白色念珠菌SLN1的无效突变在正常和高渗条件下均可存活，但在高渗透压下会导致轻微的生长迟缓。用白色念珠菌SLN1进行的Southern印迹分析揭示了相关基因的存在，其中一个与粗糙脉孢菌的NIK1基因高度同源。因此，白色念珠菌同时含有SLN1型和NIK1型组氨酸激酶。
