For those FWers who are interested in biogenetics, the following article from today's Economist may be of interest
<<<< TWO'S COMPANY The complete genomes of both the parasite that causes malaria and the mosquito that carries it have now been unravelled ANOTHER day, another genome. What was once a matter of intense scientific interest�mapping the entire genetic material of a species�has become routine. But not all genomes are equal in the sight of humanity. Details of two that are of more interest than most have just been released. Malaria has probably been the most lethal infection in history. At the moment, it is thought to kill around 2.7m people a year, 1m of them children. In addition to the suffering caused, that has huge economic consequences. Over the past 25 years, according to Jeffrey Sachs, an economist at Columbia University, the annual growth rates of countries with endemic malaria have been 1.5 percentage points lower than those in comparable non-malarial countries. Understanding the genetics of Plasmodium falciparum, the parasite that causes the disease, and of Anopheles gambiae, the mosquito that carries it, should be a big step towards correcting those numbers. Two parallel projects designed to map these genomes have been running for the past few years. Although these projects have, like all public genome-projects, been reporting results as they go along, the organisers of both have co-ordinated the formal publication that marks the point where the work is officially declared to be �done�, even if the odd gap remains here and there. The results have been carved up between Science and Nature, two leading scientific journals. Science got the mosquito and Nature the parasite. Between them, this week's issues of the two magazines have about 30 papers describing and commenting on the work, which has involved some famous institutions that have not always seen eye to eye in the past. For instance, Celera Genomics, an American biotechnology company, and the Sanger Centre, a charity-financed British laboratory, were on opposite sides in the race to sequence the human genome. Malaria has them batting on the same team. Blood brothers Biologically, the more interesting of the two creatures is Plasmodium. Mosquitoes are flies, and flies, in the shape of the geneticists' favourite fruit fly, Drosophila, have been genomically anatomised already. Plasmodium, on the other hand, is virgin territory. Although, like mosquitoes, it belongs to the eukaryotes (the group of living organisms that includes animals, plants and fungi, as well as many single-celled species), it is a peculiar example of that group. That was known before the project was started, but sequencing has confirmed Plasmodium's oddity. Since all living things are related, and lots of their biochemical processes are shared, genes are also shared�or are, at least, recognisably similar�in many species. That, however, is less true of Plasmodium than of most organisms looked at so far. About 60% of the 5,268 genes which the researchers think they have identified in this bug are new to science. On top of that, Plasmodium turns out to be closer genetically to plants than to animals. This may have something to do with its unusual evolutionary history. All eukaryotes are �compound� organisms. They contain structures called mitochondria, distant descendants of bacteria that became symbiotic with the first eukaryotic cells. In addition to their mitochondria, plants have a second relic symbiont, the chloroplast. But Plasmodium, though it lacks chloroplasts, has a relic symbiont known as an apicoplast that is not found in other eukaryotes. This is believed to be the remains of an alga and, like a mitochondrion or a chloroplast, it has a small genome of its own. It has also passed genes to Plasmodium's nucleus. Algae are plants (or at least the ancestors of plants�it depends which botanist is doing the classifying). The apicoplast seems to have given Plasmodium a lot of plant genes, too. More practically, the researchers have identified 208 genes (4% of the total) that seem to be involved in evading the immune systems of the parasite's two hosts, man and mosquito. That should help those designing vaccines against it. And, unlike other genome projects, the Plasmodium work has been going on in parallel with a proteome project, intended to identify the actual proteins for which the genes are merely the encoded instructions. This side of the research has identified 1,289 proteins. More significantly, it has shown which are produced during what stages of Plasmodium's fiendishly complicated life-cycle. That is helping to pinpoint proteins that might be suitable targets for drugs. Several of Plasmodium's digestive enzymes look promising. The DNA of Anopheles, not surprisingly for a creature that is so much bigger, turns out to have almost three times as many genes in it as does Plasmodium's. Despite the 250m years that separate it from its last common ancestor with Drosophila, its genes are reminiscent of those of its fruit-fly relative. There are differences, of course�notably in families of genes connected with immunity to infection. But there are few surprises. The hope, nevertheless, is that analysing both genomes in parallel (and also alongside that of humanity) will yield insights that would not otherwise be gleaned. And if that hope is realised it might, at last, be possible to defeat malaria. >>>> ---------------------------------------------------------------------------- -------------- Keith Hudson,6 Upper Camden Place, Bath BA1 5HX, England Tel:01225 312622/444881; Fax:01225 447727; E-mail: [EMAIL PROTECTED] ________________________________________________________________________
