Molecular organization of mating type loci in heterothallic, homothallic, and asexual Gibberella/Fusarium species

Molecular organization of mating type loci in heterothallic, homothallic, a nd asexual Gibberella/fusarium species, Fungal Genetics and Biology 31, 7-2 0, Mating type (MAT) genes were cloned from three members of the Gibberella /Fusarium complex that differ in reproductive mode: heterothallic G, fujiku roi, homothallic G. zeae, and asexual F. oxysporum, The G. fujikuroi MAT lo cus organization is typical of other heterothallic pyrenomycetes characteri zed to date; i.e., there are three genes at MAT1-1 and one at MAT1-2. G, ze ae has homologues of all four genes encoded by the two G, fujikuroi MAT idi omorphs, tightly linked on the same chromosome, interspersed with sequences unique to G, zeae. Field isolates of F. oxysporum, although asexual, have either the MAT1-1 or the MAT1-2 genes found in sexual species and these gen es are highly similar to those of heterothallic G. fujikuroi. RT-PCR analys is proved that the F. oxysporum MAT genes are expressed and that all putati ve introns found in each of the four MAT genes in G. fujikuroi and F. oxysp orum are removed, Apparent failure of F oxysporum to reproduce sexually cou ld not be attributed to mutations in the MAT genes themselves. (C) 2000 Aca demic Press.