The mating type locus of Neurospora crassa: identification of an adjacent gene and characterization of transcripts surrounding the idiomorphs.

Complexity in and around the A and a mating type idiomorphs in Neurospora crassa was examined. Six sets of transcripts surrounding the idiomorphs were identified by Northern analysis. Several different patterns of regulation were observed. The two pairs of transcripts closest to the centromere-proximal idiomorph flanks (variable regions) exhibited mating type-specific size differences. DNA sequence was obtained for the region surrounding the four transcripts which showed mating type-specific size and expression. One of these pairs encoded amino acid sequences highly similar to a domain present in the plasma membrane ATPase. A mutant allele of one of these genes was induced by repeat-induced point mutation (RIP), which resulted in altered perithecial development and the elimination of ascospore production. These transcripts comprise a cluster of genes which may be involved in the control of mating and sexual development in N. crassa.