Submitted to: International Congress on Molecular Plant-Microbe Interactions
Publication Type: Abstract only
Publication Acceptance Date: 7/17/2006
Publication Date: 7/17/2006
Citation: Jia, Y., Lin, H., Wang, Z., Lin, M.J., Valent, B., Rutger, J.N. 2006. Host active defense responses occur within 24 hours post-inoculation in the rice blast system [abstract]. XII International Congress on Molecular Plant-Microbe Interactions. p. 91. Interpretive Summary:
Technical Abstract: Knowledge of the timing of host recongition of pathogen signals is useful in understanding the mechanism of translocation of effector proteins. The Pi-ta gene in rice confers resístance to Magnaporthe grisea isolates containing the corresponding avirulence gene AVR-Pita. AVR-Pita is a metalloprotease that was shown to bind to the Pi-ta protein, a putative cytoplasmic receptor with a nucleotide binding site and leucine rich repeat triggering resístance responses. The cytological and molecular responses of the host to M. grisea were studied using a rice cultivar Katy containing Pi-ta and a Sekiguchi like-lesion mimic mutant of Katy (LmmKaty). Lesion mimic phenotype of LmmKaty was rapidly induced by virulent M. grisea isolates or by avirulent M. grisea isolates only at higher levels of inoculum. Autofluorescence was visible under ultraviolet light 24h post-inoculation in the incompatible interaction whereas, autofluorescence was not evident in the compatible interaction. Autofluorescence was also observed in LmmKaty 20h post-inoculation indicating that rapid cell death is a mechanism by which LmmKaty restricts pathogens invasion. Rapid accumulation of defense related (DR) gene transcripts, phenylalanine ammonia lyase and ß-glucanase, were observed beginning at 6 h and were obvious at 16 h and 24 h in an incompatible interaction. Rapid transcript accumulation of PR-1 and chitinase had occurred by 24h post-inoculation in an incompatible interaction. Accumulation of these transcripts was delayed in a compatible interaction. We suggest that the Pi-ta gene in rice may recognize and actively respond to the pathogen 24h post-inoculation, and autofluorescence and DR gene expression are useful markers for rapid determination of the host reaction to M. grisea.