Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 1/20/2004
Publication Date: 6/1/2004
Citation: Leong, S.A., Chauhan, R.S., Lazaro, D. 2004. Functional analysis of the rice blast resistance locus pi-co39(t) and its corresponding avr1-co39 gene from magnaporthe grisea. Rice Technical Working Group Meeting Proceedings, Louisiana State University Experiment Station. p. 116.
Technical Abstract: A new rice blast resistance locus, Pi-CO39(t), corresponding to avirulence locus, AVR1-CO39 of Magnaporthe grisea was located on the short arm of rice chromosome 11. Comparative sequence analysis of blast resistant (CO39-indica) and susceptible (Nipponbare-japonica) rice genotypes at genomic regions co-segregating with Pi-CO39(t) showed that two haplotypes are substantially diverged with respect to relative number, size, orientation and location of NBS-LRR genes. A cluster of 18 NBS-LRR disease resistance-like genes in Nipponbare haplotype (500 kb) and a cluster of 8 NBS-LRR genes in the CO39 haplotype (230 kb) has been identified at the Pi-CO39(t) locus. Both the NBS-LRR gene clusters are flanked by clusters of Serpin genes (serine/cysteine proteinase-inhibitors), which have been implicated as negative regulators of Toll-mediated antifungal defense pathway in Drosophila. Expression analysis of predicted disease resistance as well as serpin genes was performed on RNA templates isolated from rice leaves. All the NBS-LRR genes were constitutively expressed in both the haplotypes, except the RPR1 (NBR16) gene in Nipponbare, which showed induced expression in response to M. grisea infection. Two serpin genes in CO39 and one in Nipponbare showed induced expression in response to M. grisea infection. Functional analysis of these genes by complementation and gene silencing is underway and has identified one NBS-LRR gene as a probable receptor for AVR1-CO39. Orf3 of AVR1-CO39 was demonstrated to produce the active function of this avirulence gene by direct expression in resistant plant cells.