A research team at the University of Toronto in Canada has successfully tested a new strategy to identify genetic resources in the ongoing battle against plant pathogens such as bacteria, fungi, and viruses, which infect and destroy food crops worldwide. The team led by David Guttman and Darrell Desveaux wanted to know how plants defend themselves against rapidly evolving disease-causing pathogens, why disease is so uncommon even while plants are under continual attack by these highly diverse pathogens, and why domesticated crop species are so much more susceptible to pathogen attacks than wild species.
Guttman and Desveaux addressed these questions by specifically asking how a single plant is able to fight off the attacks of a common, bacterial, crop pathogen. They did this by first characterizing the global diversity of an important class of pathogen proteins, called effectors. The team sequenced the genomes of approximately 500 strains of the bacteria Pseudomonas syringae, which causes disease on nearly every major crop species. The researchers identified approximately 15,000 effectors from 70 distinct families which they reduced by identifying 530 effectors that represent their global diversity. All the representative effectors were then synthesized and put into a harmful strain of P. syringae that causes disease when infecting Arabidopsis thaliana.
"We found that over 11 percent of the effectors elicited immune response and that almost 97 percent of all P. syringae strains carry at least one immune-eliciting effector," said Desveaux. He added that they also identified new plant immune receptors that recognize these effectors and found that almost 95 percent of all P. syringae strains can be blocked by just two A. thaliana immune receptors.
(Source: Crop Biotech Update, International Service for Acquisition of Agri-Biotech Applications. www.isaaa.org)
Arabidopsis thaliana plants: healthy and bacteria-resistant (green), infected and susceptible to disease (grey). Researchers infected healthy specimens and measured abilities to fend off pathogen attacks.