Two­component histidine kinase DRK1 is required for pathogenesis in Sporothrix schenckii.

Sporothrix schenckii is a pathogenic dimorphic fungus with a global distribution. It grows in a multicellular hyphal form at 25˚C and a unicellular yeast form at 37˚C. The morphological switch from mold to yeast form is obligatory for establishing pathogenicity in S. schenckii. Two­component signaling systems are utilized by eukaryotes to sense and respond to external environmental changes. DRK1is a hybrid histidine kinase, which functions as a global regulator of dimorphism and virulence in Blastomyces dermatitidis and Histoplasma capsulatum. An intracellular soluble hybrid histidine kinase, homologous to DRK1 in B. dermatitidis, has previously been identified in S. schenckii and designated as SsDRK1. In the present study, the function of SsDRK1 was investigated using double stranded RNA interference mediated by Agrobacterium tumefaciens. SsDRK1 was demonstrated to be required for normal asexual development, yeast­phase cell formation, cell wall composition and integrity, melanin synthesis, transcription of the morphogenesis­associated gene Ste20 that is involved in the high osmolarity glycerol/mitogen­activated protein kinase pathway, and pathogenicity of S. schenckii in a murine model of cutaneous infection. Further investigations into the signals SsDRK1 responds to, and the interactions of upstream transmembrane hybrid histidine kinases with SsDRK1, are required to uncover novel targets for anti­fungal therapies.