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Antarctic and Arctic populations of the ciliate Euplotes nobilii show common pheromone-mediated cell-cell signaling and cross-mating.

ABSTRACT: Wild-type strains of the protozoan ciliate Euplotes collected from different locations on the coasts of Antarctica, Tierra del Fuego and the Arctic were taxonomically identified as the morpho-species Euplotes nobilii, based on morphometric and phylogenetic analyses. Subsequent studies of their sexual interactions revealed that mating combinations of Antarctic and Arctic strains form stable pairs of conjugant cells. These conjugant pairs were isolated and shown to complete mutual gene exchange and cross-fertilization. The biological significance of this finding was further substantiated by demonstrating that close homology exists among the three-dimensional structures determined by NMR of the water-borne signaling pheromones that are constitutively secreted into the extracellular space by these interbreeding strains, in which these molecules trigger the switch between the growth stage and the sexual stage of the life cycle. The fact that Antarctic and Arctic E. nobilii populations share the same gene pool and belong to the same biological species provides new support to the biogeographic model of global distribution of eukaryotic microorganisms, which had so far been based exclusively on studies of morphological and phylogenetic taxonomy.

SUBMITTER: Di Giuseppe G

PROVIDER: S-EPMC3044361 | biostudies-literature | 2011 Feb

REPOSITORIES: biostudies-literature

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Antarctic and Arctic populations of the ciliate Euplotes nobilii show common pheromone-mediated cell-cell signaling and cross-mating.

Di Giuseppe Graziano G Erra Fabrizio F Dini Fernando F Alimenti Claudio C Vallesi Adriana A Pedrini Bill B Wüthrich Kurt K Luporini Pierangelo P

Proceedings of the National Academy of Sciences of the United States of America 20110207 8

Wild-type strains of the protozoan ciliate Euplotes collected from different locations on the coasts of Antarctica, Tierra del Fuego and the Arctic were taxonomically identified as the morpho-species Euplotes nobilii, based on morphometric and phylogenetic analyses. Subsequent studies of their sexual interactions revealed that mating combinations of Antarctic and Arctic strains form stable pairs of conjugant cells. These conjugant pairs were isolated and shown to complete mutual gene exchange an ...[more]

PMID: 21300903

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Project description:Like many other organisms, ciliates communicate and interact socially via diffusible chemical signals, named pheromones, that are functionally associated with a genetic mating-type mechanism of cell self/not-self recognition. In Euplotes species, pheromones form species-specific families of small, globular, and disulfide-rich proteins folding into exclusively helical secondary structures. Each is specified by one of a series of high-multiple alleles that are inherited in Mendelian fashion with relationships of co-dominance at the so-called mat genetic locus of the cell transcriptionally inert micronuclear genome, and expressed in the transcriptionally active macronuclear genome as individual DNA molecules in which the central coding region is flanked by 5'-leader and 3'-trailer noncoding regions ending with C4A4/T4G4 telomeric repeats. In E. crassus, a cosmopolitan marine species with a long tradition in the study of ciliate mating systems and breeding patterns, oligonucleotides specific to amino acid sequences of pheromones Ec-1 and Ec-α were previously used to clone and sequence a first set of four structurally distinct macronuclear (mac) pheromone coding genes, mac-ec-α, mac-ec-1, mac-ec-2 and mac-ec-3, from two interbreeding strains, L-2D and POR-73. The use of these oligonucleotides in PCR amplifications of macronuclear DNA preparations from three other E. crassus interbreeding strains, ES10, Fava4 and MN4, has now resulted in the characterization of a second set of eight new pheromone coding genes, mac-ec-β, mac-ec-γ, mac-ec-δ, mac-ec-ε, mac-ec-µ, mac-ec-4, mac-ec-5 and mac-ec-6. Multiple alignment between previously and newly determined pheromone-gene sequences reinforces the concept that the E. crassus pheromone-gene family includes two sub-families, which likely reflect a duplication of the micronuclear mat gene locus and represent an apomorphic trait of the E. crassus clade. Members of one sub-family (each identified with a Greek letter) show a 500-bp 5'-leader noncoding region rich in AGGA/AGGGA repetitions, and encode 56-amino acid pheromones with eight conserved Cys residues. Members of the other sub-family (each identified with an Arabic numeral) show an 800-bp 5'-leader noncoding region without AGGA/AGGGA repetitions, and encode 45-amino acid pheromones with ten conserved Cys residues.

Dataset Information

Antarctic and Arctic populations of the ciliate Euplotes nobilii show common pheromone-mediated cell-cell signaling and cross-mating.

Publications

Antarctic and Arctic populations of the ciliate Euplotes nobilii show common pheromone-mediated cell-cell signaling and cross-mating.

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