Genes and means

gene exchange between different plant species is facilitated by their parasites, according to a report authored by biologists from the us -based Indiana University of Bloomington (iub). They found that genes could move from plant parasites to plant hosts. The finding adds to a report also by the us academia -- the University of Michigan and the Smithsonian Institution; published in the July 30, 2004 issue of the journal Science, it states the opposite: genes can move from plant hosts to plant parasites.

Taken together, the findings establish plant parasitism as the first known medium for horizontal gene transfer -- the exchange of genes between individuals of different species. "Other mechanisms are likely to exist, but as of yet, they remain in the realm of speculation," says biologist Jeff Mower, the lead author of the iub report.

The document cites many examples of horizontal gene transfer. The best illustration is the transfer of the important mitochondrial gene atp1 from parasitic flowering plants to weeds in the genus Plantago. Three Plantago species possess a normal, a functioning version and a defective copy of atp1; this is similar to the atp1 pattern found in parasitic dodders in the plant genus Cuscuta. Evidence suggests Plantago acquired the defective atp1 via horizontal transfer a few million years ago. The dodders' manner of attacking plants indicates how the dna could have travelled between the parasite and the host -- as part of their parasitism, dodder cells penetrate the cells of their hosts, making it possible for any errant parasite dna to sidestep obstacles on its way into a host cell.