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Evidence for Gene Duplication and Allelic Codominance (not Hierarchical Dominance) at the Mating‐Type Locus of the Ciliate, Euplotes crassus
Author(s) -
Vallesi Adriana,
Alimenti Claudio,
Federici Sergio,
Di Giuseppe Graziano,
Dini Fernando,
Guella Graziano,
Luporini Pierangelo
Publication year - 2014
Publication title -
journal of eukaryotic microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.067
H-Index - 77
eISSN - 1550-7408
pISSN - 1066-5234
DOI - 10.1111/jeu.12140
Subject(s) - biology , mating type , locus (genetics) , genetics , gene , pheromone , sex pheromone , gene duplication , allele , phenotype , coding region
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 (E c ‐α and E c ‐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 E c ‐α pheromone of L‐2D cells. The other two pheromones were shown to be new and were designated E c ‐2 and E c ‐3 to denote their structural homology with the E c ‐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.