A role for the MAP kinase gene MKC1 in cell wall construction and morphological transitions in Candida albicans

Departamento de Microbiología II, Facultad de Farmacia, Universidad Complutense de Madrid, Plaza de Ramón y Cajal s/n, E-28040 Madrid, Spain Sección Departamental de Microbiología, Facultad de Farmàcia, Universidad de València, Avinguda Vicent Andrés Estellés, E-46100 Burjassot, València, Spain ABSTRACT The Candida albicans MKC1 gene encodes a mitogen-activated protein (MAP) kinase, which has been cloned by complementation of the lytic phenotype associated with Saccharomyces cerevisiae slt2 ( mpk1 ) mutants. In this work, the physiological role of this MAP kinase in the pathogenic fungus C. albicans was characterized and a role for MKC1 in the biogenesis of the cell wall suggested based on the following criteria. First, C. albicans mkc1 / mkc1 strains displayed alterations in their cell surfaces under specific conditions as evidenced by scanning electron microscopy. Second, an increase in specific cell wall epitopes ( O -glycosylated mannoprotein) was shown by confocal microscopy in mkc1 / mkc1 mutants. Third, the sensitivity to antifungals which inhibit (1,3)-β-glucan and chitin synthesis was increased in these mutants. In addition, evidence for a role for the MKC1 gene in morphological transitions in C. albicans is presented based on the impairment of pseudohyphal formation of mkc1 / mkc1 strains on Spider medium and on the effect of its overexpression on Sacch. cerevisiae colony morphology on SLADH medium. Using the two-hybrid system, it was also demonstrated that MKC1 is able to interact specifically with Sacch. cerevisiae Mkk1p and Mkk2p, the MAP-kinase kinases of the PKC1 -mediated route of Sacch. cerevisiae , and to activate transcription in Sacch. cerevisiae when bound to a DNA-binding element. These results suggest a role for this MAP kinase in the construction of the cell wall of C. albicans and indicate its potential relevance for the development of novel antifungals. Author for correspondence: Jesús Pla. Tel: +34 1 3941744. Fax: +34 1 3941745. e-mail: jesuspla@eucmax.sim.ucm.es Keywords: MAP kinase, pseudohyphal growth, antifungal, two-hybrid system, confocal microscopy