FUNCTIONAL-ANALYSIS OF THE HOMEODOMAIN-RELATED PROTEINS OF THE A-ALPHA LOCUS OF SCHIZOPHYLLUM-COMMUNE

DNA-mediated transformation was used to correlate function with putative genes from three alternative A-alpha-mating-type loci (A-alpha-1, A-alpha-3, and A-alpha-4) of Schizophyllum commune. Each DNA was tested in at least nine haploid strains, one for each of the - nine A-alpha-mating types found in the world-wide population of S. commune. The Y and Z genes (tentatively identified by sequence analysis elsewhere) individually activate A-alpha-regulated development when transformed into any strain with a different A-alpha-mating type. The only exceptions are when the Y alleles of A-alpha-3 or A-alpha-4 (i.e., Y3 or Y4, respectively) are introduced into an A-alpha-1 strain (the A-alpha-1 locus encodes Y1 but lacks a Z gene). These observations indicate that A-alpha-regulated development is activated by the interaction (direct or indirect) of products from different genes (e.g., Z3 and Y1) rather than from different alleles of the same gene (e.g., Y1 and Y3). Therefore, the activating interaction is of the form Z(i)Y(j) where i not-equal j and i and j are the A-alpha-mating types from which the Z and Y polypeptides, respectively, are derived. Transformations with truncated or mutagenized genes begin to define essential regions of the genes and their products. Activity is in some cases dependent upon the particular A-alpha-mating type of the recipient. A working hypothesis for the activation of A-alpha-regulated development is proposed.