title: Dispersal and evolution of the Sinorhizobium meliloti group II RmInt1 intron in bacteria that interact with plants.
abstract: Group II introns are both self-splicing RNAs and mobile retroelements found in bacterial and archaeal genomes and in organelles of eukaryotes. They are thought to be the ancestors of eukaryote spliceosomal introns and non-long terminal repeat retrotransposons. We show here that RmInt1, a bacterial group II intron first described in the nitrogen-fixing symbiont of alfalfa (Medicago sativa) Sinorhizobium meliloti, is also present in other Sinorhizobium and Rhizobium species. The intron-homing sites in these species are IS elements of the ISRm2011-2 group as in S. meliloti, but ectopic insertion is also observed. We present evidence that these related bacteria have acquired RmInt1 by vertical inheritance from a common ancestor and by independent horizontal transfer events. We also show that RmInt1 is mobile in related taxa of bacteria that interact with plants and tends to evolve toward an inactive form by fragmentation, with loss of the 3' terminus including the intron-encoded protein. Our results provide an overview of the evolution and dispersion of a bacterial group II intron.
authors.affiliation: Grupo de Ecología Genética, Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, calle Profesor Albareda 1, Granada, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Fernández-López
authors.forename: Estefanía
authors.initials: E
authors.lastname: Muñoz-Adelantado
authors.forename: Moniek
authors.initials: M
authors.lastname: Gillis
authors.forename: Anne
authors.initials: A
authors.lastname: Willems
authors.forename: Nicolás
authors.initials: N
authors.lastname: Toro
mesh_terms: D001419:Bacteria; D001483:Base Sequence; D019143:Evolution, Molecular; D005798:Genes, Bacterial; D016680:Genome, Bacterial; D007438:Introns; D000455:Medicago sativa / Q000382:microbiology; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010802:Phylogeny; D010944:Plants / Q000382:microbiology; D016133:Polymerase Chain Reaction; D012313:RNA / Q000235:genetics; D012326:RNA Splicing; D018626:Retroelements; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D016962:Sinorhizobium meliloti / Q000235:genetics*
chemical_list: D018626:Retroelements; D012313:RNA