Pheromone and pheromone-gene sequences from the marine ciliate, Euplotes crassus
A new set of eight full-length gene-size DNA molecules have been cloned and sequenced from the transcriptionally active macronuclear genome of interbreeding strains of the marine ciliate, Euplotes crassus. The determination of these new sequences reinforces the concept that the phylogenesis of E. crassus (and most likely of its closely related species, E. minuta and E. vannus) is characterized by a phenomenon of duplication of the Mendelian mat (mating-type) locus of the germinal micronuclear genome. The result of this duplication is that the E. crassus pheromone genes are subdivided into two subfamilies, one encoding 56-amino acid pheromones with eight conserved Cys residues and one encoding 45-amino acid pheromones with ten conserved Cys residues.
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Macronuclear DNA preparations were amplified using primers designed on conserved sequences adjacent to the telomeric ends and previously determined from other E. crassus pheromone coding genes. Amplicons were cloned, plasmids of five distinct clones were Sanger-sequenced in both directions, and partial sequences were overlapped to produce the complete gene sequences.