Alex L A, Borkovich K A, Simon M I
Division of Biology, California Institute of Technology, Pasadena, 91125, USA.
Proc Natl Acad Sci U S A. 1996 Apr 16;93(8):3416-21. doi: 10.1073/pnas.93.8.3416.
Two-component signal transduction systems are most often found in prokaryotic organisms where they are responsible for mediating the cellular responses to many environmental stimuli. These systems are composed of an autophosphorylating histidine kinase and a response regulator. We have found evidence for the existence of two-component histidine kinases in the eukaryotic filamentous fungus Neurospora crassa based on screening with degenerate primers to conserved regions of these signaling proteins. Subsequent cloning and sequencing of one member of this newly discovered group, nik-1+, shows that the predicted protein sequence shares homology with both the kinase and response regulator modules of two-component signaling proteins. In addition, the N-terminal region of the protein has a novel repeating 90-amino acid motif. Deletion of the nik-1+ gene in N. crassa results in an organism that displays aberrant hyphal structure, which is enhanced under conditions of high osmostress. Increased osmotic pressure during growth on solid medium leads to restricted colonial growth, loss of aerial hyphae formation, and no subsequent conidiophore development. This finding may have implications for mechanisms of fungal colonization and pathogenicity.
双组分信号转导系统最常见于原核生物中，它们负责介导细胞对许多环境刺激的反应。这些系统由一个自磷酸化组氨酸激酶和一个反应调节因子组成。基于用简并引物筛选这些信号蛋白的保守区域，我们发现了真核丝状真菌粗糙脉孢菌中存在双组分组氨酸激酶的证据。随后对这个新发现的组中的一个成员nik-1+进行克隆和测序，结果表明预测的蛋白质序列与双组分信号蛋白的激酶和反应调节因子模块均具有同源性。此外，该蛋白质的N端区域有一个新的重复90个氨基酸的基序。粗糙脉孢菌中nik-1+基因的缺失导致一种显示出异常菌丝结构的生物体，在高渗透压胁迫条件下这种异常会加剧。在固体培养基上生长期间渗透压升高会导致菌落生长受限、气生菌丝形成丧失以及随后没有分生孢子梗发育。这一发现可能对真菌定殖和致病性的机制有影响。
