"Basically the BIK1 protein does this by regulating a plant defense hormone called salicylic acid," he said. "The amount of salicylic acid determines the type and level of a plant's response to the pathogen. This is very important in terms of disease resistance.

"In this paper, we speculate that there is an optimum level of salicylic acid that is required for pathogen defense. When that level is exceeded, in some cases it may promote susceptibility to other pathogens by interfering with other defense strategies of the plants."

The research team first looked at normal plants and then at the BIK1 mutant when they began to study the effect of different hormones on plant growth and pathogen defense, Mengiste said. The scientists were surprised to find that the mutants had reduced primary root growth but increased numbers of root hairs. Along with their other findings, this revelation is leading the scientists to future research.

"It looks like this gene actually links pathogen response to plant growth and development," Mengiste said. "But how a single protein regulates these two processes that are singularly independent, we don't know. That is the main purpose of our future studies.

"We need to figure out the details of how it regulates root growth and the length and amount of root hair. This may have implications in terms of nutrient absorption or total plant biomass."

The answers eventually could lead to increased crop yield and decreased produce loss due to Botrytis and other similar pathogens, he said.

Currently, the gray mold disease caused by Botrytis destroys about 10 percent of the grape crop annually and about 25 percent to 30 percent of tomato and str
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Contact: Susan A. Steeves
ssteeves@purdue.edu
765-496-7481
Purdue University
3-Feb-2006