Only one of the paired Schizophyllum commune A alpha mating-type, putative homeobox genes encodes a homeodomain essential for A alpha-regulated development.
The A alpha mating-type locus is one of four master regulatory loci controlling sexual development in Schizophyllum commune. The A alpha locus contains two homeobox genes, Y and Z, encoding two homeodomain-related proteins, Y and Z. Y and Z are each multiallelic genes. When haploid strains form fusion cells, only particular combinations of Y and Z alleles activate A alpha-regulated sexual development. The role of the putative homeodomain was examined in several Y and Z alleles by site-directed mutagenesis of regions critical to secondary structure and function of homeodomains. Mutations of the Z homeobox do not affect the function of Z proteins in A alpha-activated development, but mutations of Y homeoboxes destroy the ability of Y proteins to activate development. We conclude that only one of two A alpha homeodomain-related regulators relies upon the homeodomain motif to effect gene expression in sexual development. This conclusion affords a refinement of our working hypothesis for the mechanism by which A alpha proteins may regulate target gene expression. On the basis of our results with the Z protein, we speculate that the DNA-binding motifs of some transcriptional regulators may be lost or modified during evolution once these regulators have been recruited to participate in complexes with other DNA-binding proteins.
Luo
Y
Y
Department of Microbiology and Molecular Genetics, University of Vermont, Burlington 05405.
Ullrich
R C
RC
Novotny
C P
CP
D000595:Amino Acid Sequence; D004252:DNA Mutational Analysis; D005656:Fungal Proteins / Q000235:genetics; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal / Q000235:genetics*; D005801:Genes, Homeobox / Q000235:genetics*; D049770:Genes, Mating Type, Fungal; D000072235:Mating Factor; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009024:Morphogenesis / Q000235:genetics; D016297:Mutagenesis, Site-Directed; D010455:Peptides / Q000235:genetics*; D017433:Protein Structure, Secondary; D012098:Reproduction / Q000235:genetics; D012567:Schizophyllum / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D014170:Transformation, Genetic
D005656:Fungal Proteins; D010455:Peptides; D000072235:Mating Factor