Mutational analysis of a regulatory gene for morphogenesis in Schizophyllum

Knowledge of the structure and function of a complex gene regulating sexual development in the mushroom, Schizophyllum commune, has come from the analysis of various mutations in a chromosomal region known as the Bbeta incompatibility gene. This gene is one of two linked genes, Balpha and Bbeta, that together comprise the B factor which regulates a developmental sequence known as the B-sequence. The B-sequence is normally "turned off" unless alleles of different specificity of either Balpha or Bbeta are combined in a heterokaryon resulting from the mating of two individuals. Various mutations have been found in the Bbeta gene that range in effect from dominant, always-on, through a number of intermediate stages of changes in specificity and function, to recessive, always-off. There is evidence that the Bbeta gene operates via a positive control mechanism and involves at least four functions, one of which has been shown to be separable by recombination.