June 8, 2012
Parasitic Plants Are Stealing Genes From Their Hosts
New research published today in BioMed Central's open access journal BMC Genomics reveals that the Malaysian parasitic plant Rafflesia cantleyi, with its 50cm diameter flowers, has 'stolen' genes from its host Tetrastigma rafflesiae. Analysis of these genes shows that their functions range from respiration to metabolism, and that some of them have even replaced the parasites own gene activity.
Vertical gene transfer is that between parents and their offspring, while horizontal gene transfer is the movement of genes between two different organisms. Bacteria use horizontal gene transfer to exchange resistance to antibiotics. Recent studies have shown that plants can also use horizontal gene transfer, especially parasitic plants and their hosts due to their intimate physical connections.
Most of these genes had been integrated into the parasite's nucleus, allowing the researchers to perform genomic analysis. Over time DNA randomly mutates and investigation of genetic drift between the genes for these transcripts, between the parasite and host, showed that some time has passed since the genes were acquired and that they were acquired gradually.
Prof Charles Davis, from the Harvard University Herbaria, who co-led this project with Prof Joshua Rest from Stony Brook University, explained, "The elevated rate of horizontal gene transfer between T. rafflesiae and its parasite R. cantleyi raises the possibility that there is a 'fitness' benefit to the parasite. For example they may improve the parasites ability to extract nutrients from the host, or help it evade the host's defences, as has been seen for a bacterial pathogen of citrus trees."
Prof Davis continued, "Furthermore it appears that about one third of the parasites own genes have evolved to be more like those of T. rafflesia. Finding out how T. rafflesia manages its genomic deception will provide us with real insights into the slow war between plant parasites and their hosts."
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