title: Genetic interactions among homologous recombination mutants in Candida albicans.
abstract: rad52-ΔΔ and, to a lesser extent, rad51-ΔΔ deletants of Candidaalbicans displayed slow growth and aberrant filamentous morphology whereas rad59-ΔΔ mutants, both by growth rate and morphology resembled wild type. In this study, we have constructed pair-wise double deletants to analyze genetic interactions among these homologous recombination (HR) proteins that affect growth and morphology traits. When grown in liquid YPD medium, double mutant rad51-ΔΔ rad59-ΔΔ exhibited growth rates, cell and colony morphologies, and plating efficiencies that were not significantly different from those observed for rad51-ΔΔ. The same was true for rad52-ΔΔ rad59-ΔΔ compared to rad52-ΔΔ. Slow growth and decreased plating efficiency were caused, at least in part, by a decreased viability, as deduced from FUN1 staining. Flow cytometry and microscopic studies of filamentous mutant populations revealed major changes in cell ploidy, size and morphology, whereas DAPI staining identified complex nuclear rearrangements in yeast and filamentous cells. These phenotypes were not observed in the rad59-ΔΔ mutant populations. Our results show that abolishing Rad51 functions induces the appearance of a subpopulation of aberrant yeast and filamentous forms with increased cell size and ploidy. The size of this complex subpopulation was exacerbated in rad52-ΔΔ mutants. The combination of filamentous cell morphology and viability phenotypes was reflected on the colony morphology of the respective mutants. We conclude that the rad52 mutation is epistatic to rad51 for all the morphological traits analyzed. We discuss these results in the light of the several functions of these recombination genes.
authors.affiliation: Departamento de Ciencias Biomédicas, Área de Microbiología, Facultad de Ciencias, Universidad de Extremadura, 06071 Badajoz, Spain.
authors.forename: Alberto
authors.initials: A
authors.lastname: Bellido
authors.affiliation: Departamento de Ciencias Biomédicas, Área de Microbiología, Facultad de Ciencias, Universidad de Extremadura, 06071 Badajoz, Spain.
authors.forename: Encarnación
authors.initials: E
authors.lastname: Andaluz
authors.affiliation: Departamento de Ciencias Biomédicas, Área de Microbiología, Facultad de Ciencias, Universidad de Extremadura, 06071 Badajoz, Spain.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Gómez-Raja
authors.affiliation: Servicio de Técnicas Aplicadas a la Biociencia, Universidad de Extremadura, 06071 Badajoz, Spain.
authors.forename: Alberto
authors.initials: A
authors.lastname: Álvarez-Barrientos
authors.affiliation: Departamento de Ciencias Biomédicas, Área de Microbiología, Facultad de Ciencias, Universidad de Extremadura, 06071 Badajoz, Spain. Electronic address: glarriba@unex.es.
authors.forename: Germán
authors.initials: G
authors.lastname: Larriba
mesh_terms: D002176:Candida albicans / Q000166:cytology / Q000235:genetics*; D049109:Cell Proliferation; D048429:Cell Size; D002470:Cell Survival; D002869:Chromosome Aberrations; D004843:Epistasis, Genetic; D005434:Flow Cytometry; D005656:Fungal Proteins / Q000235:genetics*; D055786:Gene Knockout Techniques; D059765:Homologous Recombination; D008853:Microscopy; D009154:Mutation; D011003:Ploidies; D051135:Rad51 Recombinase / Q000235:genetics*; D051721:Rad52 DNA Repair and Recombination Protein / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics
chemical_list: D005656:Fungal Proteins; D051721:Rad52 DNA Repair and Recombination Protein; D029701:Saccharomyces cerevisiae Proteins; D051135:Rad51 Recombinase
keywords: Aberrant cell morphology viability; Candida albicans; RAD51; RAD52; RAD59