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Category: The Parasite Files • Upcoming Talks
Posted on: November 7, 2006 9:56 AM, by Carl Zimmer
Attention all Loom readers in the Cornell University area: I'm heading up to Ithaca to give a talk tomorrow on a subject near and dear to my heart--how parasites turn their hosts into puppets and slaves. I'll be at the David Call auditorium in Kennedy Hall at 4 pm. The lecture is open to the public and will, of course, include a very creepy Powerpoint. Details here, map here.
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Comments
correction. zombie carl will be appearing at cornell, giving a speech dictated by his parasites. you're not fooling anyone, parasites ... carl seems to know just a little too much about the subject
Posted by: snaxalotl | November 7, 2006 1:48 PM
Great talk today!
The most interesting part scientifically was the question about which of a parasite's traits are evolutionarily adaptive and which are only incidental. The blind watchmaker's watch vs. the spandrel.
The most powerful approach to this question is genetics. Knock out or modify the trait genetically (or find natural genetic variations), and test whether it affects the parasitic interaction.
This approach is quite easy to do in some cases, but not (yet) in most of the fascinating examples you discussed. It's easier for bacterial and viral parasites (aka pathogens, same thing). Primarily because their short generation times allow accelerated evolution. In addition some viruses like influenza have high mutation rates and correspondingly large numbers of progeny per generation. John Barry's The Great Influenza is excellent about influenza virus evolution.
You didn't mention the evolution of hosts in response to the parasites. (It was only an hour's talk.) For example the selection of hemoglobin genes resistant to malaria's sickle-cell-anemia effects. In the world of plant parasites there are fascinating examples of "gene-for-gene" coevolution, one resistance gene in the host corresponding to each of the parasite's genes for virulence, and vice versa, a coevolutionary arms war. This is an ongoing coevolution in real time, year to year. Right now a new mutation in the wheat parasite, stem rust, threatens to spread worldwide before plant breeders can find and deploy a resistance gene to prevent devastation. Norman Borlaug and millions of research dollars are involved in this effort. - - - - - - - - - - - - - - - - - - - - David E. Matthews, Ph.D. USDA-ARS Plant Genome Database Curator Cornell University Email: matthews@greengenes.cit.cornell.edu Department of Plant Breeding Phone: +1-607-255-9951 409 Bradfield Hall Fax: +1-607-255-6683 Ithaca, New York 14853, USA GrainGenes: http://wheat.pw.usda.gov
Posted by: Dave Matthews | November 8, 2006 9:42 PM
Parasitic plants are another topic you didn't have time to mention. Orobanche,
the broomrape, is amazing. A snapdragon with no leaves, nothing
green, just the showy flower spike and an organ that saps all its nutrition
from the host (tomato, sunflower, others).
How does a parasitic plant find its victims, the hosts for its next generation? Each Orobanche flower makes thousands of tiny seeds, nearly microscopic. These seeds sift down into the soil and wait. For years. Until a root of their host plant grows very close, ca. 2 mm. Not until then will the seed germinate, detecting a specific chemical exuded from the root. The minuscule germinated root invades the host's root, and by summer there's a fine Orobanche flower spike and a very sick tomato.
Orobanche is an economically important parasite in some places, e.g. for tomato in Israel and chickpea in southern Europe. A related species, Striga (witchweed) is a serious problem for maize and sorghum in sub-Saharan Africa, and has become established in North Carolina where eradication efforts have been ongoing for twenty years.
Posted by: Dave Matthews | November 8, 2006 10:59 PM
Great talk today!
The most interesting part scientifically was the question about which of a parasite's traits are evolutionarily adaptive and which are only incidental. The blind watchmaker's watch vs. the spandrel.
The most powerful approach to this question is genetics. Knock out or modify the trait genetically (or find natural genetic variations), and test whether it affects the parasitic interaction.
This approach is quite easy to do in some cases, but not (yet) in most of the fascinating examples you discussed. It's easier for bacterial and viral parasites (aka pathogens, same thing). Primarily because their short generation times allow accelerated evolution. In addition some viruses like influenza have high mutation rates and correspondingly large numbers of progeny per generation. John Barry's The Great Influenza is excellent about influenza virus evolution.
You didn't mention the evolution of hosts in response to the parasites. (It was only an hour's talk.) For example the selection of hemoglobin genes resistant to malaria's sickle-cell-anemia effects. In the world of plant parasites there are fascinating examples of "gene-for-gene" coevolution, one resistance gene in the host corresponding to each of the parasite's genes for virulence, and vice versa, a coevolutionary arms war. This is an ongoing coevolution in real time, year to year. Right now a new mutation in the wheat parasite, stem rust, threatens to spread worldwide before plant breeders can find and deploy a resistance gene to prevent devastation. Norman Borlaug and millions of research dollars are involved in this effort.
Posted by: Dave Matthews | November 8, 2006 11:26 PM