Their overview in Science includes illustrated descriptions of the disease-resistance or immunity pathways in the mouse, Drosophila fruit fly, rice and a common research plant known as Arabidopsis. These represent the immune defense systems of vertebrates, insects, monocotyledons (grass-like plants) and dicotyledons (plants like beans that have two seed leaves.)
The researchers note that plant biologists led the way in discovering receptors that sense and respond to infection. The 1980s brought about an intense hunt for the genes that control production of the receptor proteins, followed by an "avalanche" of newly discovered receptor genes and mechanisms in the 1990s.
Another milestone included discovery in 2000 of the immune receptor in Arabidopsis known as FLS2 -- which demonstrated that a plant receptor could bind to a molecule that is present in many different microbial invaders.
The review also discuses how plant and animal immune responses have evolved through the years and which mechanisms have remained the same.
While the past 15 years have been rich in significant discoveries related to plant and animal immunity, Beutler and Ronald are quick to point out that researchers have just scratched the surface.
"If you think of evolution as a tree and existing plant and animal species as the leaves on the tips of the tree's branches, it is clear that we have examined only a few of those leaves and have only a fragmentary impression of what immune mechanisms exist now and were present in the distant past," said Beutler, an elected member of the U.S. National Academy of Sciences.
He and Ronald predict that, as results from new gene sequencing projects become available, scientists will likely find that some plant and animal species emphasize specific resistance mechanisms while having little use for others.
For example, the research
|Contact: Pat Bailey|
University of California - Davis