Ithaca, New York
May 31, 2002

Findings could improve crop plant disease resistance and lead to new therapies for human infection

A team of scientists from the Boyce Thompson Institute for Plant Research (BTI) and Cornell University has made a significant advance in understanding how plants defend themselves against disease.

For the first time, they have identified a small region present in two bacterial proteins that triggers natural immunity to speck disease in tomato plants.

The finding, which was published in today's issue of the journal 'Cell,' ultimately may lead to ways to improve disease resistance in crop plants and, therefore, reduce pesticide use. It could also provide leads for developing new therapies to fight human infections that are caused by some bacteria, such as Salmonella and E. coli.

It is known that many bacteria cause disease in plants and humans by injecting certain proteins - called "effector" proteins - into host cells. It is also known that some plants produce "resistance" proteins that intercept and bind to the bacterial proteins. The binding of the plant and bacterial proteins activates the plant's natural defense response, which inhibits the growth of the pathogen, and, in turn, helps protect the plant from disease. Discovering the mechanism behind this binding event was the goal of the BTI/Cornell research.

In their paper, Young Jin Kim, Ph.D., a BTI scientist; Nai-Chun Lin, a Cornell graduate student; and Gregory Martin, Ph.D., a BTI scientist and professor of plant pathology at Cornell, report for the first time that two very different effector proteins (AvrPto and AvrPtoB) produced by the same Pseudomonas syringae bacterium bind to a single plant resistance protein (Pto) in tomato leaf cells - an event that activates the plant's immunity to bacterial speck disease. The Pto resistance gene protects the crop from the disease and is present in many tomato varieties grown throughout the world.

Significantly, the BTI/Cornell team discovered that, despite their differences, the two bacterial proteins have a small region of similarity and that this common segment is involved in the binding of the plant protein to the bacterial proteins. "Research into a plant/bacterium recognition event such as this one sheds new light on plant disease resistance and may lead to an improved understanding of the function of bacterial effector proteins in human disease," according to co-author Martin. "Our research provides new information that may provide general insights into how hosts recognize and defend themselves against bacterial pathogens."

The next phase of the team's research will focus on understanding the structure of the effector and plant proteins and studying how they interact in three-dimensional space.

The Boyce Thompson Institute for Plant Research, located at Cornell University in Ithaca, N.Y., USA, is a private, not-for-profit organization dedicated to the study of plants and associated organisms for the betterment of society. Created by endowment in 1924, the Institute maintains a dedicated staff of research scientists and collaborates with a large number of public and private organizations around the world.