|ZHOU, ERXUN - South China Agricultural University|
|LEE, SEONGHEE - University Of Florida|
Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/7/2016
Publication Date: 6/13/2016
Publication URL: http://handle.nal.usda.gov/10113/62662
Citation: Jia, Y., Zhou, E., Lee, S., Bianco, T.A. 2016. Coevolutionary dynamics of rice blast resistance gene Pi-ta and Magnaporthe oryzae avirulence gene AVR-Pita 1. Phytopathology. 106(7):676-683. doi: org/10.1094/PHYTO-02-16-0057-RVW.
Interpretive Summary: Rice blast disease caused by the fungus Magnaporthe oryzae is one of the most damaging diseases of rice (Oryza sativa) in the US and worldwide. The use of major resistance genes in rice has been effective in preventing blast disease epidemics. However, the pathogen can overcome resistance by changing it’s avirulence gene that is essential for the plant’s resistance response. In this review, we demonstrate how genomic information has accelerated our understanding of genetic variation of the major blast resistance gene Pi-ta, its association with rice productivity, genetic variation of the corresponding avirulence gene AVR-Pita1 that triggers Pi-ta-mediated disease resistance, and the coevolution of Pi-ta and AVR-Pita1 in Oryza species and M. oryzae populations, respectively. We review the genetic and molecular bases of the Pi-ta and AVR-Pita interaction, and evaluate the potential to develop long lasting broad-spectrum resistance in elite rice cultivars with the aid of diagnostic DNA markers.
Technical Abstract: The Pi-ta gene in rice is effective in preventing infections by Magnaporthe oryzae strains that contain the corresponding avirulence gene, AVR-Pita1. Genome sequencing and mapping studies demonstrated that AVR-Pita1 is highly unstable, and diverse haplotypes of AVR-Pita1 have been identified from isolates of M. oryzae from rice production areas in the US and worldwide. DNA sequencing, expression analysis, and QTL mapping of the Pi-ta locus reveal the complex of evolutionary mechanisms in Pi-ta mediated resistance. A single resistance Pi-ta haplotype was associated with a transposable element at the promoter region, suggesting that a transposon mechanism can play an important role in Pi-ta gene expression. Several Pi-ta transcripts were identified, most of which are probably derived from alternative splicing and exon skipping, which could produce functional resistance proteins that support a new concept of coevolution of Pi-ta and AVR-Pita1. User friendly DNA markers for Pi-ta have been developed to support marker assisted selection, and development of new rice varieties with the Pi-ta markers. Genome-wide association studies revealed a link between Pi-ta mediated resistance and yield components suggesting that rice has evolved a complicated defense mechanism against the blast fungus. Pyramiding of more than one major blast resistance gene in any single rice variety provides resistance to an overlapping spectra of pathotypes, and is recommended for effective crop protection.