Mosaic origins of a complex chimeric mitochondrial gene in Silene vulgaris

Štorchová H., Müller K., Lau S., Olson MS.
PLOS ONE 7: e30401, 2012

Keywords: plant mitochondria, novel genes, cytoplasmic male sterility, gene conversion
Abstract: Chimeric genes are significant sources of evolutionary innovation and are normally created when portions of two or more protein coding regions fuse to form a new open reading frame. In plant mitochondria astonishingly high numbers of different novel chimeric genes have been reported, where they are generated through processes of rearrangement and recombination. Nonetheless, because most studies do not find or report nucleotide variation within the same chimeric gene, evolution after the origination of these chimeric genes remains unstudied. We show that although two divergent versions of a complex chimera in Silene vulgaris share the same general structure, they are divergent in nucleotide sequence to the extent that their common origin is not detectable within regions derived from functional mitochondrial gene homologs. Structural patterns suggest a history partially influenced by gene conversion between the chimeric gene and functional copies of subunit 1 of the mitochondrial ATP synthase gene (atp1). In addition, both genomic environment and strength of expression are divergent between the two versions. We identified small repeat structures within the chimeras that are likely recombination sites allowing generation of the chimera. These results establish the potential for chimeric gene divergence in different plant mitochondrial lineages within the same species, most likely resulting from long residence times of the genes within the species. This result contrasts with the absence of diversity within mitochondrial chimeras found in crop species.
IEB authors: Karel Müller, Helena Štorchová