Differential expression of the 45 kDa protein (actin) during the dimorphic transition of Sporothrix schenckii.

We investigated the gene expression of a protein during the dimorphic transition from yeast to mycelial form of Sporothrix schenckii. Yeast cells were converted to mycelial cells in Sabouraud glucose broth at 25 degrees C. After 1, 3 and 5 days of culture, the intermediate form of cells between yeast and mycelium was obtained, and after 7 days these cells were morphologically similar to the mycelial cells. Proteins having the molecular weight of 45 kDa were found to by synthesized preferentially by intermediate form of day 7 and mycelial cells. On the other hand, the 45 kDa proteins were predominantly translated by the RNA isolated from the intermediate of day 7 and mycelial cells using in vitro cell-free translation assay. The 45 kDa proteins synthesized by mycelial cells were found to be identical with the 45 kDa translation products directed by the mRNA isolated from the intermediate and mycelial cells by V8 protease peptide mapping. The 45 kDa protein was considered to be actin by Western blot analysis using an anti-actin monoclonal antibody. These results suggest that the intermediate form of day 7 has the same phenotypes in the morphology and biosynthesis of actin as those of mycelial cells. The expression of the actin gene may be involved in the dimorphic transition of S. schenckii.