ARS | Publication request: Understanding the molecular mechanisms of the instability of rice blast resistance

Submitted to: Plant and Animal Genome
Publication Type: Proceedings
Publication Acceptance Date: January 1, 2010
Publication Date: January 9, 2010
Citation: Jia, Y. Understanding the molecular mechanisms of the instability of rice blast resistance. In: Proceedings of Plant and Animal Genome XVIII Conference, January 9-13, 2010, San Diego, CA. p. 521.

Technical Abstract: Race-specific blast resistance is not durable and the molecular mechanisms of the instability of race-specific resistance are unclear. The pathogenicity factor AVR-Pita in Magnaporthe oryzae that determines the efficacy of the resistance gene Pi-ta encodes a predicted metalloprotease. Here we report the evidence suggesting that M. oryzae employs a range of genetic mechanisms to overcome Pi-ta mediated resistance: 1) transposon insertion at the coding region of AVR-Pita; 2) partial deletion at the 5’ amino terminal region; 3) complete AVR-Pita deletion; and 4) frameshift mutations resulting in truncated AVR-Pita proteins. Significant DNA sequence variation of AVR-Pita was observed in avirulent field isolates. Most DNA sequence alterations resulted in amino acid substitutions in the AVR-Pita protein. Most interestingly, the putative zinc-binding domain of the AVR-Pita protease was found intact in 27 avirulent proteins in isolates from rice fields in major rice-producing countries around the globe. These findings suggest that AVR-Pita is an important pathogenicity factor for rice blast fungus and AVR-Pita is under diversified selection.