Mosaic Origins of a Complex Chimeric Mitochondrial Gene in Silene vulgaris

Chimeric genes are significant sources of evolutionary innovation that 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. Here we identify two alleles of a complex chimera in Silene vulgaris that are divergent in nucleotide sequence, genomic position relative to other mitochondrial genes, and expression patterns. 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). 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. This result contrasts with the absence of diversity within mitochondrial chimeras found in crop species

Atom-probe tomography characterization of the oxidation of stainless steel

Three-dimensional atomic characterization of oxidation in stainless steels under simulated nuclear reactor conditions has been achieved with atom-probe tomography (APT). By combining high spatial resolution and high chemical sensitivity, the ingress of oxygen and other trace elements has been studied on an "atom-by-atom" basis, together with their interaction with microstructural defects. APT has revealed how the highly dislocated microstructure in cold-worked stainless steels accelerates the oxidation and the formation of oxide precursors beyond the oxide-metal interface. © 2010 Acta Materialia Inc