GENTECH archive


Fw: Horizontal gene transfer-new evidence

>Below is an important development reported by Mae Wan Ho
>(Natural Law Party Wessex)
>Date: 04 December 1998 15:55
>Subject: Horizontal gene transfer-new evidence
>Please circulate this message to whoever may be interested.
>Horizontal gene transfer - new evidence
>A group of researchers in Indiana University of the United States, headed by
>Dr. Jeffrey Palmer, have just reported in the current issue of the
>Proceedings of the National Academy of Sciences USA that a genetic parasite
>belonging to yeast has suddenly jumped into many unrelated species of higher
>plants recently.
>This parasite is a piece of DNA called a group I intron that can splice
>itself in and out of a particular gene in the genome of mitochondria.
>Mitochondria are little power houses of the cell that oxdize food in order
>to turn it into a form of energy that can be used for all living processes.
>Until 1995, this parasite was thought to be confined to yeast and only one
>genus of higher plants out of the 25 surveyed had the parasite. But in a new
>survey of species from 335 genera, 48 were found to have the parasite.
>Moreover, all the higher plants that have gained the group I intron has the
>same one, as the DNA base sequence is more than 92% identical.
>When this intron jumps into a genome, it also adds to its tail end an extra
>stretch of DNA that does not belong to the host. By comparing this extra
>tail, the researchers are able to conclude that almost all of the horizontal
>gene transfer events were independent and must have occurred very recently.
>"This massive wave of lateral transfers is of entirely recent occurrence,
>perhaps triggered by some key shift in the intron's invasiveness within
>angiosperms [i.e., higher plants]"
>So, what triggered this recent explosive invasion of the higher plants by
>the particular genetic parasite? It could have got into the plant cells by
>being carried in viruses, insects or bacteria. In order to get into the
>genome, however, it has to overcome species barriers. For example, the
>genome has to have a specific site of about 20 base pairs that is recognized
>by the parasite. Furthermore, in order for the splicing gene carried by the
>parasite to become expressed, it has to have a signal that is recognized by
>the host.
>The researchers themselves raise concerns about releasing transgenic crops
>into the environment, if horizontal gene transfer is so widespread.
>Only two months ago, it was reported in the Journal Nature that genes
>transferred into transgenic plants can be up to 30 times more likely to
>escape than the plant's own genes.
> Is it possible that the recent massive horizontal gene transfer from yeast
>to higher plants was triggered by commercial genetic engineering
>biotechnology itself?
> Genetic engineering makes use of artificial genetic parasites as gene
>carriers, to transfer genes horizontally between unrelated species. These
>artificial parasites are made from parts of the most aggressive naturally
>occurring parasites like the group 1 intron discussed here.
> The same kinds of explosive horizontal gene transfer have already been
>documented among viruses and bacteria which are responsible for the recent
>resurgence of drug and antibiotic resistant infectious diseases (reviewed by
>Ho et al, Microbial Ecology in Health and Disease vol 10, 33-39m 1998).
> We should take this new evidence very, very seriously. There should be an
>immediate moratorium on further releases of transgenic plants, in particular
>those carrying antibiotic resistance genes like the Novartis maize.