The Great Gene Giveaway

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Science  09 Mar 2012:
Vol. 335, Issue 6073, pp. 1149
DOI: 10.1126/science.335.6073.1149-a

The vast majority of genes in eukaryotes are inherited vertically; that is, they are transferred through sexual or asexual reproduction from parent(s) to offspring (i.e., from one generation to the next). Prokaryotes are not quite so obliging. Among bacteria and archea, there is a substantial amount of lateral (or horizontal) gene transfer; that is, genes being exchanged between unrelated organisms independent of reproduction.

Christin et al. use comparative studies of DNA sequences (phylogenetics) to provide evidence of repeated lateral gene transfers occurring in plants. Different species of the grass lineage Alloteropsis use either the C3 or the more recently evolved C4 photosynthetic pathway to fix carbon from the air. Analysis of two enzymes critical for the C4 pathway reveals that individual C4 Alloteropsis species seem to have picked up these nuclear genes from four other genera of grass: Setaria palmifolia, found in South Africa; Themeda quadrivalvis, in Australia; and a Cenchrinae species; with the first transfer, from Melinidinae, occurring before the species divergence of Alloteropsis. Lateral transfer may have occurred because of the close physical proximity of the different plant species, all of which are wind-pollinated, resulting in the transfer of pollen between them. Acquisition of the C4 genes may then have provided a selective advantage, because C4 is more efficient than C3 photosynthesis.

Curr. Biol. 10.1016/j.cub.2012.01.054 (2012).

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