A G protein alpha subunit from Cochliobolus heterostrophus involved in mating and appressorium formation

A G alpha subunit-encoding gene (CGA1) was cloned from Cochliobolus heterostrophus, a heterothallic foliar pathogen of corn. The deduced amino acid sequence showed similarity to G alpha proteins from other filamentous fungi and suggested that CGA1 is a member of the G alpha(i) class. cga1 mutants had reduced ability to form appressoria on glass surfaces and on corn leaves; mutants nevertheless caused lesions on corn plants like those of wild type. cga1 mutants were female sterile; sexual development was completely abolished when the mutant allele was homozygous in a cross. Ascospores produced in crosses heterozygous at Cga1 were all wild type. The signal transduction pathway represented by CGA1 appears to be involved in developmental pathways leading to either appressorium formation or mating; in sexual development CGA1 is required for both fertility and ascospore viability. (C) 1999 Academic Press.