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Something fishy about a soil microbe
By Adam Marcus

A microbe that lives in soil and harms plants has an unlikely genetic cousin in the Japanese pufferfish. Both creatures have a version of a gene called ros.

Clarence I. Kado, who studies plant pathogens at the University of California, Davis, and his colleagues made the ros connection while investigating virulence genes in Agrobacterium tumefaciens, a microbe that causes tumors in plants. The gene did not look like a bacterial gene, so they searched computer databases for similar genes in other species. Ros turned up in marine-dwelling bacteria but not in plants.

Broadening their search, the researchers found a version of ros in the Japanese pufferfish, or Fugu rubripes. This organism has been sequenced and its genome is a model for interpreting the human genome. Humans have a distantly related version of the ros gene.

Kado believes the aquatic ancestors of A. tumefaciens may have passed ros on to the pufferfish or its relatives. These marine bacteria might have been living in the fish. Or the fish may have acquired the gene by eating an organism containing the bacterium.

Maynard Olson, a University of Washington geneticist who helped sequence A. tumefaciens, agrees that these scenarios are plausible. But he says it's difficult to rule out the alternative possibility that the ros gene is ancient and belonged to the last-common ancestor of bacteria and vertebrates. Over time it might have been retained in the pufferfish but lost in most other vertebrates.

See related GNN articles
»Pufferfish genome reveals nearly a thousand potentially new human genes
»The Genome of Agrobacterium tumefaciens

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Kado, C. et al. Negative transcriptional regulation of virulence and oncogenes of the Ti plasmid by Ros bearing a conserved C(2)H(2)-zinc finger motif. Plasmid 48, 179-185 (November 2002).

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