title: Early stages of functional diversification in the Rab GTPase gene family revealed by genomic and localization studies inParameciumspecies.
abstract: New gene functions arise within existing gene families as a result of gene duplication and subsequent diversification. To gain insight into the steps that led to the functional diversification of paralogues, we tracked duplicate retention patterns, expression-level divergence, and subcellular markers of functional diversification in the Rab GTPase gene family in threeParamecium aureliaspecies. After whole-genome duplication, Rab GTPase duplicates are more highly retained than other genes in the genome but appear to be diverging more rapidly in expression levels, consistent with early steps in functional diversification. However, by localizing specific Rab proteins inParameciumcells, we found that paralogues from the two most recent whole-genome duplications had virtually identical localization patterns, and that less closely related paralogues showed evidence of both conservation and diversification. The functionally conserved paralogues appear to target to compartments associated with both endocytic and phagocytic recycling functions, confirming evolutionary and functional links between the two pathways in a divergent eukaryotic lineage. Because the functionally diversifying paralogues are still closely related to and derived from a clade of functionally conserved Rab11 genes, we were able to pinpoint three specific amino acid residues that may be driving the change in the localization and thus the function in these proteins.
authors.affiliation: Department of Biology, Indiana University, Bloomington, IN 47405 lydjbright@gmail.com brightl@newpaltz.edu.|Department of Biology, State University of New York at New Paltz, New Paltz, NY 12561.
authors.forename: Lydia J
authors.initials: LJ
authors.lastname: Bright
authors.affiliation: Department of Biology, Indiana University, Bloomington, IN 47405.
authors.forename: Jean-Francois
authors.initials: JF
authors.lastname: Gout
authors.affiliation: Department of Biology, Indiana University, Bloomington, IN 47405.
authors.forename: Michael
authors.initials: M
authors.lastname: Lynch
mesh_terms: D000818:Animals; D005075:Biological Evolution; D019143:Evolution, Molecular; D020440:Gene Duplication; D018503:Genome, Protozoan; D023281:Genomics; D010247:Paramecium / Q000201:enzymology* / Q000235:genetics*; D010802:Phylogeny; D059467:Transcriptome; D020691:rab GTP-Binding Proteins / Q000235:genetics* / Q000378:metabolism*
chemical_list: D020691:rab GTP-Binding Proteins