[Analysis and mapping of homologous sequences of barley disease resistance gene Mlo and maize disease resistance gene Hm1 in rice]

Abstract

The encoding products of the disease resistance (R) gene of barley, Mlo, and the maize R gene, Hm1, do not contain the recognizable structural domains of most of the known plant R gene products. The two genes do not comply with the gene-for-gene theory in the response to pathogen infection either. Two sequences, OsMlo-1 and DFR-1 which were homologous to the barley Mlo and maize Hm1, respectively, were isolated from rice. The OsMlo-1 was mapped between two molecular markers, RZ667 and RG424, and located at a distance of 20.6 centi-Morgan (cM) from RZ667 and 6.0 cM from RG424 on rice chromosome 6. The DFR-1 was flanked by molecular markers R2635 and RG462 with an estimated genetic distance of 11.3 cM from R2635 and 23.9 cM from RG462 on rice chromosome 1. Using other published rice molecular linkage maps as references, it was found that the chromosomal locations of OsMlo-1 and DFR-1 were correspondence with two previously identified rice blast resistant QTLs (quantitative trait loci), respectively. The results suggest that the genes homologous to barley Mlo and maize Hm1 in rice may be involved in defense responses induced by pathogen infection.