Signaling via the G protein α subunit FGA2 is necessary for pathogenesis in Fusarium oxysporum

Cloning and disruption offigal, the gene encoding the G protein a subunit FGA1 in phytopathogenic fungus Fitsarium oxysporum, has been reported previously, and the fgal disruptants showed altered colony morphology, increased heat resistance, reduced conidiation and pathogenicity. To further evaluate the role of G protein signaling in this fungus, cloning of fga2, which encodes the second Galpha protein FGA2, was performed by PCR methods. The deduced primary structure of FGA2 (355 amino acid residues) showed high identity with other Galpha proteins, which belong to class III of fungal Got proteins. Disruption offg(12 led to higher heat resistance, similar to the fgal disruptants, but pathogenicity was completely lost, unlike the fgal disruptants. Alteration of colony morphology and conidiation, which was observed in the fgal disruptants, was not observed in the fga2 disruptants. The figal/fga2 double disruptants showed phenotypic alterations similar to the fgal or fga2 single disruptants, but increase of heat resistance was much more pronounced than in each single disruptant. (C) 2004 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.