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Abstract Detail



Bryological and Lichenological Section/ABLS

Liu, Yang [1], Medina, Rafael [1], Goffinet, Bernard [2].

The evolution of mitochondrial genomes in mosses.

Mitochondria trace their evolutionary origin to an endosymbiotic bacterium. A signature of this ancestry is the presence of a genome with prokaryotic features within the organelle. Like its analogue, the chloroplast genome, the mitochondrial genome has undergone significant changes in terms of composition and organization. The rate of evolution of the mitochondrial genome differs significantly between plants and animals, with nucleotide substitutions occurring at a slower pace in plants. In contrast to exon sequenced being highly conserved among land plants, the order of the genes is highly variable, in particular among flowering plants. In contrast, the mitochondrial genomes of the two mosses sampled so far are completely alignable as are the three liverwort genomes. As is the case in their potential sister group, the vascular plants, the mt genomes of hornworts may be reorganized during cladogenic events. The mt genome of mosses is much smaller than that of angiosperms, and overall the trend among land plants, the trend is one of increase in size, due to the lengthening of intergenic spacers. We sought to test the hypothesis that the mt genome of mosses is indeed highly static despite the old age of the lineage, which originated in the Devonian. We sampled 12 taxa spanning the Moss tree of Life, and assembled their mitochondrial genome from shotgun sequences obtained using the Illumina platform. Within mosses the mt genome is largest in Sphagnum with a size 40% larger than that of Physcomitrella and decreases rapidly to reach a stable size of slightly over 100MB within arthrodontous mosses. The composition of the genome is highly conserved with only one gene pseudogenized and two introns lost in Tetraphis and Buxbaumia, one intron lost in Hypnum and two “gained” in Sphagnum. In pairwise comparisons the variation within homologous regions is rather evenly distributed. The lability of the organellar genomes may be linked of the presence and distributions of small repeats that would allow for intragenomic recombinations. Such prediction is confirmed in mosses, which lack small repeats but does not match the pattern in liverworts, which exhibit at least some repeats. It is possible that the lack of rearrangements of the mt genome in mosses is due to efficient repair mechanisms, controlled by nuclear genes.

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1 - University of Connecticut, Ecology and Evolutionary Biology, 75 NorthEagleville road, Storrs, Connecticut, 06269, United States
2 - University of Connecticut, Department of Ecology & Evolutionary Biology, 75 N. Eagleville Road, U-3043, STORRS, CT, 06269-3043, USA

Keywords:
bryophyte
genome evolution
mitochondrial genome
mosses
small organellar repeats.

Presentation Type: Oral Paper:Papers for Sections
Session: 29
Location: Ascot/Riverside Hilton
Date: Tuesday, July 30th, 2013
Time: 2:30 PM
Number: 29006
Abstract ID:559
Candidate for Awards:None


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