Self-compatible B mutants in coprinus with altered pheromone-receptor specificities.
A successful mating in the mushroom Coprinus cinereus brings together a compatible complement of pheromones and G-protein-coupled receptors encoded by multiallelic genes at the B mating-type locus. Rare B gene mutations lead to constitutive activation of B-regulated development without the need for mating. Here we characterize a mutation that arose in the B6 locus and show that it generates a mutant receptor with a single amino acid substitution (R96H) at the intracellular end of transmembrane domain III. Using a heterologous yeast assay and synthetic pheromones we show that the mutation does not make the receptor constitutively active but permits it to respond inappropriately to a normally incompatible pheromone encoded within the same B6 locus. Parallel experiments carried out in Coprinus showed that a F67W substitution in this same pheromone enabled it to activate the normally incompatible wild-type receptor. Together, our experiments show that a single amino acid replacement in either pheromone or receptor can deregulate the specificity of ligand-receptor recognition and confer a self-compatible B phenotype. In addition, we use the yeast assay to demonstrate that different receptors and pheromones found at a single B locus belong to discrete subfamilies within which receptor activation cannot normally occur.
Olesnicky
N S
NS
Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom.
Brown
A J
AJ
Honda
Y
Y
Dyos
S L
SL
Dowell
S J
SJ
Casselton
L A
LA
D000595:Amino Acid Sequence; D002628:Chemoreceptor Cells / Q000502:physiology*; D002874:Chromosome Mapping; D015825:Chromosomes, Fungal / Q000235:genetics*; D003302:Coprinus / Q000235:genetics*; D003433:Crosses, Genetic; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology*; D005816:Genetic Complementation Test; D016297:Mutagenesis, Site-Directed; D010675:Pheromones / Q000235:genetics; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D005656:Fungal Proteins; D010675:Pheromones; D011994:Recombinant Proteins