A potential phosphorylation site for an A-type kinase in the Efg1 regulator protein contributes to hyphal morphogenesis of Candida albicans.
Efg1p in the human fungal pathogen Candida albicans is a member of the conserved APSES class of proteins regulating morphogenetic processes in fungi. We have analyzed the importance for hyphal morphogenesis of a putative phosphorylation site for protein kinase A (PKA), threonine-206, within an Efg1p domain highly conserved among APSES proteins. Alanine substitution of T206, but not of the adjacent T207 and T208 residues, led to a block of hypha formation on solid and in liquid media, while a T206E exchange caused hyperfilamentation. The extent of the morphogenetic defect caused by the T206A mutation depended on hypha-induction conditions. Extragenous suppression of mutations in signaling components, including tpk2 and cek1 mutations, was achieved by wild-type- and T206E-, but not by the T206A-variant-encoding allele of EFG1. All muteins tested were produced at equal levels and at high production levels supported pseudohyphal formation. The results are consistent with a role of Efg1p as a central downstream component of a PKA-signaling pathway including Tpk2p or other PKA isoforms. Threonine-206 of Efg1p is essential as a putative phosphorylation target to promote hyphal induction by a subset of environmental cues.
Bockmühl
D P
DP
Institut für Mikrobiologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany.
Ernst
J F
JF
D000409:Alanine / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D002176:Candida albicans / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D005656:Fungal Proteins; D014644:Genetic Variation; D009024:Morphogenesis; D010766:Phosphorylation; D013912:Threonine / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*
D004268:DNA-Binding Proteins; C121438:EFG1 protein, Candida albicans; D005656:Fungal Proteins; D014157:Transcription Factors; D013912:Threonine; D017868:Cyclic AMP-Dependent Protein Kinases; D000409:Alanine