"Effector" protein discovery in Phytophthora sojae is important to understand the mechanism of pathogenesis
Phytophthora sojae is a plant pathogen that affects the soybean industry worldwide. The economic losses in the United States alone are estimated to be $2 million annually. P. sojae grows on live plant tissues initially, followed by growing on dead plant tissues. During the early part of the infection, a specialized structure is formed. This structure is thought to transport carbon, water, and nutrients by exploiting the plant cells, and to deliver “effector” proteins to modulate plant defense and help the pathogen colonize the plant.
Virginia Tech researchers Dou et al., in collaboration with researchers from China and the Netherlands, used expression studies to demonstrate Avr1b is an “effector” protein, which stimulates the virulence of the pathogen through suppressing the host response to pathogen. This delays the programmed cell death in the host plant (soybean) and it is assumed that the pathogen establishes on the host plant during that time. The bioinformatics analysis showed that three motifs (sections) in the C-terminal (back end) region of the protein are conserved in all “effector” proteins across Phytophthora species.
The research also showed that the Avr1b “effector” protein triggers the plant resistance gene Rps1b mediated host response to delay the programmed cell death. The discovery is reported in the April 2008 Plant Cell Journal published by the American Society of Plant Biologists.
This is the first direct demonstration of an “effector” protein in Phytopthora species that is positively contributing to the virulence of the pathogen through delaying the host plant’s response by interacting to a host resistant gene. In addition to the understanding of the mechanism of pathogenesis, this research may help to develop resistant plants to Phytophthora species.
This research was supported by the National Research Initiative Microbial Biology and Microbial Genomics Programs.
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