Dispersion of the RmInt1 group II intron in the Sinorhizobium meliloti genome upon acquisition by conjugative transfer.
RmInt1 is a self-splicing and mobile group II intron initially identified in the bacterium Sinorhizobium meliloti, which encodes a reverse transcriptase-maturase (Intron Encoded Protein, IEP) lacking the C-terminal DNA binding (D) and DNA endonuclease domains (En). RmInt1 invades cognate intronless homing sites (ISRm2011-2) by a mechanism known as retrohoming. This work describes how the RmInt1 intron spreads in the S.meliloti genome upon acquisition by conjugation. This process was revealed by using the wild-type intron RmInt1 and engineered intron-donor constructs based on ribozyme coding sequence (DeltaORF)-derivatives with higher homing efficiency than the wild-type intron. The data demonstrate that RmInt1 propagates into the S.meliloti genome primarily by retrohoming with a strand bias related to replication of the chromosome and symbiotic megaplasmids. Moreover, we show that when expressed in trans from a separate plasmid, the IEP is able to mobilize genomic DeltaORF ribozymes that afterward displayed wild-type levels of retrohoming. Our results contribute to get further understanding of how group II introns spread into bacterial genomes in nature.
Nisa-Martínez
Rafael
R
Grupo de Ecología Genética de la Rizosfera, Estación Experimental del Zaidín Consejo Superior de Investigaciones Científicas, Profesor Albareda 1, 18008 Granada, Spain.
Jiménez-Zurdo
José I
JI
Martínez-Abarca
Francisco
F
Muñoz-Adelantado
Estefanía
E
Toro
Nicolás
N
D001426:Bacterial Proteins / Q000737:chemistry; D001483:Base Sequence; D003227:Conjugation, Genetic; D005816:Genetic Complementation Test; D005818:Genetic Engineering; D016680:Genome, Bacterial; D007438:Introns; D008969:Molecular Sequence Data; D012329:RNA, Bacterial / Q000737:chemistry; D016337:RNA, Catalytic / Q000737:chemistry; D018626:Retroelements; D016962:Sinorhizobium meliloti / Q000235:genetics*
D001426:Bacterial Proteins; D012329:RNA, Bacterial; D016337:RNA, Catalytic; D018626:Retroelements