ABSTRACT
A protein kinase C (PKC)-encoding gene (pkcA) was isolated from the filamentous fungus Aspergillus nidulans. Although we attempted to isolate pkcA deletion mutants, we obtained only heterokaryons that had both DeltapkcA and pkcA(+) nuclei. Conidia produced by the heterokaryon germinated. The germ tubes, however, lysed frequently and no colony formation was observed, indicating that the pkcA gene is essential to the viability of A. nidulans. We constructed conditional mutants (alcA(p)-pkcA mutants) that expressed pkcA under the control of the alcA promoter (alcA(p)). Under alcA(p)-repressing conditions, their colonies were smaller than those of the wild-type strains and their hyphae lysed frequently. These phenotypes were not remedied under moderate- or high-osmolarity conditions; the growth defect deteriorated further under the latter. Under alcA(p)-inducing conditions, the alcA(p)-pkcA mutants also showed growth-sensitivity to cell wall destabilizing agents. These results indicate that pkcA plays an important role in the maintenance of cell integrity.
Subject(s)
Aspergillus nidulans/enzymology , Fungal Proteins/physiology , Protein Kinase C-alpha/physiology , Aspergillus nidulans/cytology , Aspergillus nidulans/genetics , Fungal Proteins/classification , Fungal Proteins/genetics , Gene Deletion , Genes, Fungal , Phylogeny , Protein Kinase C-alpha/classification , Protein Kinase C-alpha/genetics , Transcriptional ActivationABSTRACT
Concentrations above the MIC of caspofungin allow growth of some Candida isolates. A strain demonstrating paradoxical growth was grown in the presence and absence of caspofungin, and the cell wall content was analyzed. Beta-1,3-glucan declined 81% in the presence of caspofungin, as expected. Beta-1,6-glucan declined 73%. Chitin increased 898%, demonstrating a mechanism for paradoxical growth-a rapid shift in the key polymer.
