Submitted to: American Phytopathology Society
Publication Type: Proceedings
Publication Acceptance Date: 7/15/2008
Publication Date: 7/22/2008
Citation: Dai, Y., Jia, Y., Wang, X., Lee, F.N., Wang, Y., Correll, J.C. 2008. Structural and functional analysis of the rice blast fungus avirulence gene AVR-Pita. American Phytopathology Society. 98:S44. Interpretive Summary:
Technical Abstract: The AVR-Pita gene in Magnaporthe oryzae determines efficacy of resistance stability provided by a major effective resistance gene Pi-ta in rice. AVR-Pita encodes a predicted secreted metalloprotease that appears to interact with the Pi-ta protein, a cytoplamic NBS-LRR protein directly in triggering resistance. To determine how structure change of the AVR-Pita gene impacts the effectiveness of resistance a total of 100 isolates from US and a few other rice production areas have been used for sequence analysis and pathogenicity assay. To date, the 5’ leader, open reading frame and 3’ trailer of AVR-Pita (1086 bp) have been sequenced in 70 isolates. An open reading frame encoding a protein with 224 amino acids was identified with a few amino acid substitutions or additions in all avirulent isolates. Insertion of two nucleotides was identified in the first exon leading frame shifts in 5 virulent isolates collected in China. Four major clades were identified by phylogenetic analysis of nucleotide and amino acid respectively. Overall, sequence variations were observed throughout the 1086 bp region. More sequence variations were identified leading to amino acid substitution than silent mutation in the exons. Consistently, the corresponding fragment of AVR-Pita has not been amplified by PCR except one virulent isolate 60/1-5. Progress in sequencing analysis of 60/1-5 in the promoter region and pathogenicity assays of a set of fungal isolates from US, and functional determination of AVR-Pita using fungal transformation will be presented.