Symbioses: Plant, Animal, and Microbe Interactions
Chen, Yu , Halterman, Dennis .
Characterization of RB-mediated Late Blight Resistance Phenotype.
Late blight, caused by the oomycete pathogen Phytophthora infestans, continues to be the most devastating disease for potato cultivation. The resistance (R) gene RB, cloned from the wild potato species Solanum bulbocastanum, offers durable, broad spectrum and non-race specific resistance to late blight. To better understand the resistance mechanism mediated by RB, we examined the interaction between P. infestans and transgenic RB-containing potato SP951 (Katahdin plus RB), using the susceptible potato Katahdin as the control. Three week old SP951 and Katahdin plants were inoculated with a high concentration (150,000 sporangia/ml) of P. infestans sporangia. Hypersensitive cell death (HR) was monitored at 0, 8, 12, 24, 48, and 72 hours after inoculation. Both micro-HR (only one or several neighboring cells) and macroscopic lesions were evident at each time point in the transgenic plants. In some cases, hyphae could be seen growing beyond the HR, demonstrating the rate-limiting nature of this R gene. Leaves were harvested at the same time points for RNA extraction. Quantitative real-time reverse transcription PCR results showed that the transcriptional level of two pathogenesis related genes, PR1 basic and PR4, hallmarks of systemic acquired resistance (SAR), increased sharply 8 hours after inoculation and then decreased gradually after that in SP951, while in the susceptible plants, no significant difference or very small increases were detected. Our results suggest that RB is sufficient to induce HR and SAR immediately after inoculation and the first 8 hours is critical for resistance initiation. These results also indicate that rate-limiting R genes may use molecular mechanisms similar to the better-studied class of R genes conferring immunity to pathogens.
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1 - University of Wisconsin-Madison, Plant Pathology Department, 1630 Linden Dr., Madison, Wisconsin, 53706, U.S.
2 - USDA-ARS; University of Wisconsin-Madison, Vegetable Crop Research Unit,; Plant Pathology Department, 1630 Linden Dr., Madison, Wisconsin, 53706, U.S.
systemic acquired resistance.
Presentation Type: Poster:Posters for Topics
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM