Targeted disruption of a G protein alpha subunit gene results in reduced pathogenicity in Fusarium oxysporum.

The cloning of fga1, the gene encoding a G protein alpha subunit, was performed by standard PCR techniques and by screening a Fusarium oxysporum genomic library, using the PCR product as a probe. The full-length open reading frame spanned 1,059 nucleotides and the deduced primary structure of the protein (353 amino acid residues) showed high identity to those of G protein alpha(i) family proteins from other filamentous fungi. Disruption of fga1 had no effect on vegetative growth, but reduced the conidiation and pathogenicity of the fungus. Disruptants also showed a decreased level of intracellular cAMP and increased resistance to heat shock at 45 degrees C. These results suggest that the Galpha subunit encoded by fga1 is involved in a signal transduction pathway in F. oxysporum that controls conidiation, heat resistance and pathogenicity.