Evolution and mechanism ofmitochondrial cox1 intron horizontal transfer in Angiosperms.

FEDERICO LUIS CERIOTTI; LAURA EVANGELINA GARCIA; SANCHEZ-PUERTA, M. VIRGINIA

Quebec

Congreso; Eastern Regional Meeting 2017 Canadian Society of Plant Biologists; 2017

Canadian Society of Plant Biologists

The mostfrequent case of horizontaltransfer in angiosperms involves thegroupintron in the cox1 mitochondrial gene, originally acquired froma fungal donor and followedmore than 100 subsequent inferredplant-to-plant transfer events. This promiscuous behaviourthought tobe due to its encoded DNA homing endonuclease, whose cleavage site isinintron-less alleles. The study of homologous introns in yeastsuggests that intron insertion occurs through the double-strand breakrepair (DSBR) pathway without crossover, process called intronhoming. So, this mechanismbeen proposed to participate inangiospermsintron propagation. However, other repair mechanismssupposed to occur in plant mitochondria could participate. Thesemechanismscan be distinguished becauseare supposed to generate crossovers (CO)and/ornon-crossovers(NCO) in different proportions. In order to detect possiblealternative repairmechanismsinvolved in cox1 intron propagation, we analyzed 139 angiospermspecies withintron. The analysis consisted in the identification ofCO and NCO events comparing exon1, exon2 and intron phylogeneticrelationships. When sequences were available the analysesextended tointergenic regions flanking the exons. In contrast with original DSBRmodel, where COs and NCOs are expected to occur in similarproportions, only NCO events where detectedour analyses. We proposean alternative repair pathway called synthesis-dependent strandannealing (SDSA), which can only produce NCO results, as the mostprobable mechanism involved in the cox1 intron propagation inangiospermp { margin-bottom: 0.1in; line-height: 115%; }