title: Evidence for gene duplication and allelic codominance (not hierarchical dominance) at the mating-type locus of the ciliate, Euplotes crassus.
abstract: The high-multiple mating system of Euplotes crassus is known to be controlled by multiple alleles segregating at a single locus and manifesting relationships of hierarchical dominance, so that heterozygous cells would produce a single mating-type substance (pheromone). In strain L-2D, now known to be homozygous at the mating-type locus, we previously identified two pheromones (Ec-α and Ec-1) characterized by significant variations in their amino acid sequences and structure of their macronuclear coding genes. In this study, pheromones and macronuclear coding genes have been analyzed in strain POR-73 characterized by a heterozygous genotype and strong mating compatibility with L-2D strain. It was found that POR-73 cells contain three distinct pheromone coding genes and, accordingly, secrete three distinct pheromones. One pheromone revealed structural identity in amino acid sequence and macronuclear coding gene to the Ec-α pheromone of L-2D cells. The other two pheromones were shown to be new and were designated Ec-2 and Ec-3 to denote their structural homology with the Ec-1 pheromone of L-2D cells. We interpreted these results as evidence of a phenomenon of gene duplication at the E. crassus mating-type locus, and lack of hierarchical dominance in the expression of the macronuclear pheromone genes in cells with heterozygous genotypes.
authors.affiliation: Laboratory of Eukaryotic Microbiology and Animal Biology, University of Camerino, 62032, Camerino, MC, Italy.
authors.forename: Adriana
authors.initials: A
authors.lastname: Vallesi
authors.forename: Claudio
authors.initials: C
authors.lastname: Alimenti
authors.forename: Sergio
authors.initials: S
authors.lastname: Federici
authors.forename: Graziano
authors.initials: G
authors.lastname: Di Giuseppe
authors.forename: Fernando
authors.initials: F
authors.lastname: Dini
authors.forename: Graziano
authors.initials: G
authors.lastname: Guella
authors.forename: Pierangelo
authors.initials: P
authors.lastname: Luporini
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D016798:Ciliophora / Q000235:genetics*; D020440:Gene Duplication; D008969:Molecular Sequence Data; D010675:Pheromones / Q000235:genetics*; D012098:Reproduction
chemical_list: D010675:Pheromones
keywords: Cell chemical signals; ciliate mating types; conjugation; macronuclear gene-size DNA molecules; protein pheromones