Sustained cell polarity and virulence in the phytopathogenic fungus Ustilago maydis depends on an essential cyclin-dependent kinase from the Cdk5/Pho85 family.
Cyclin-dependent kinases from the Cdk5/Pho85 family are thought to play important roles in morphogenesis in organisms as diverse as yeast and humans. Here we used the corn smut fungus Ustilago maydis to address the role of Cdk5/Pho85 kinases in the morphogenesis and virulence of dimorphic phytopathogens. We found that Cdk5 is essential for growth in U. maydis. A temperature-sensitive cdk5 mutant caused cell wall and morphology defects at the restrictive temperature. Actin patches labeled with a fimbrin-GFP fusion protein were delocalized and a GFP-Myo5 fusion was directed towards the growing cell pole and rapidly dissociated from the tip. These defects were found to be due to an impairment in the maintenance of cell polarity. Our results indicated that Cdk5 is required for the activity of Rac1, probably at the level of the localization of its GEF, Cdc24. Cdk5 was required for full virulence, probably because mutant cells are unable to sustain the dramatic polar growth required for the formation of the infective structures. These results support a major role for morphogenesis in the virulence program of dimorphic fungi.
Castillo-Lluva
Sonia
S
Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología CSIC, 28049 Madrid, Spain.
Alvarez-Tabarés
Isabel
I
Weber
Isabella
I
Steinberg
Gero
G
Pérez-Martín
José
J
D000199:Actins / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002455:Cell Division / Q000235:genetics / Q000502:physiology; D002467:Cell Nucleus / Q000378:metabolism; D002473:Cell Wall / Q000378:metabolism; D002686:Chitin / Q000032:analysis / Q000378:metabolism; D051360:Cyclin-Dependent Kinase 5 / Q000235:genetics / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D016195:G2 Phase / Q000235:genetics / Q000502:physiology; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism; D008840:Microfilament Proteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D020929:Mitogen-Activated Protein Kinase Kinases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D024701:Myosin Type V / Q000378:metabolism; D010802:Phylogeny; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014588:Ustilago / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D014774:Virulence; D003313:Zea mays / Q000382:microbiology; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism
D000199:Actins; D018797:Cell Cycle Proteins; D005656:Fungal Proteins; D008562:Membrane Glycoproteins; D008840:Microfilament Proteins; D011993:Recombinant Fusion Proteins; C026742:plastin; D002686:Chitin; D049452:Green Fluorescent Proteins; D051360:Cyclin-Dependent Kinase 5; C089988:Fuz7 protein, Ustilago maydis; D020929:Mitogen-Activated Protein Kinase Kinases; D024701:Myosin Type V; D020830:rac1 GTP-Binding Protein