Constitutive Nest Aspergillus Calcineurin And Its Related Proteins In Response To Adversity And Morphogenesis Regulatory Mechanism Research

The well developed genetic system of Aspergillus nidulans(A. nidulans) makes it an excellent model system for studying the processes of growth, establishment and maintenance of polarity.It has been reported that calcium signaling plays an important role in polarized morphogenesis, but information concerning the effect of the key regulator of calcium signaling in establishment and maintenance of polarity is limited. Our previous study indicated that CotA kinase, a member of the NDR protein kinase family, forms a complex with MobB to regulate cell polarized growth in Aspergillus nidulans. MobB/CotA defects could be suppressed by the osmotic stress in the presence of external calcium.In this study, via the genetic and molecular approach, we further demonstrated that Ca2+permeable stretch-activated nonselective cation channel-MidA, calcium/calmodulin-dependent protein phosphatase catalatic subunit-CnaA and external calcium were required for the osmotic stabilizer-coupled suppression. The up-regulation of calcium/calcineurin signaling pathway induced by osmotic stress might be the reason for bypassing the requirements of NDR kinase complex, which is otherwise necessary for polar morphogenesis.In addition, we demonstrated that cnaA mutant is more sensitive to exogenous calcium than crzA mutant strain and this phenotype indicated that CrzA is not the only target of calcineurin. We further deduce CdaA, FapA and AkrA as the interacted proteins of calcineurin via homologous sequence comparison. CdaA is a polysaccharide deacetylase and its loss of function doesn’t have obvious phenotype defects. FapA, which has NF-X1-type zinc finger motifs, locates in nuclear and its mutant display sensitive to EGTA. AkrA has five transmembrane domains and its mutant sensitive to EGTA, NaCl and LiCl. These results demonstrated that these three proteins have different relationship with calcium signaling and AkrA plays the most important role in maintaining intercellular ionic homeostasis.