Letter: Temporal allelic interaction, a new kind of dominance.

Abstract

Ustilago violacea has a simple bipolar heterothallic mating system, with two alleles a1 and a2 of the mating-type locus. Haploid yeast-like cells of opposite mating type conjugate on a medium free of nutrients1. Earlier reports from this laboratory using diploid, triploid and tetraploid cells showed that allele a2 is dominant in log phase cultures (heterozygous cells conjugate with cells homozygous for a1 but not cells homozygous for a2). Heterozygous cells in stationary phase cultures failed to mate even though all the stationary phase homozygous cells mated actively. Consequently, the dlominance of allele a2 is termed age-related2.