The Study Of The Homologs Of Maize Hml And Barley Mlo Gene In Rice

Mlo and Hml are two special genes that don't comply with the gene-for-gene theory. Mlo encodes a membrance protein, and its recessive mutant gene mlo confers barley resistance to nearly all races of barley powdew mildew (Erysiphe graminis f.sp. hordei). Hml encodes HC-toxin reduclase and contributes maize resistance to Cochliobolus carbonum race 1. So it's important for us to research their homologs in rice.for its disease resistance study.In this study, we designed three specific primers for Mlo, and Mlo's homologous gene: OSMlo-hl. Hml's homologous gene: DFR Fragments was amplified by PCR in barley cultivar TR306. rice culuvars LTH and 'leqmg. Three fragments named as Mlo-1, OSMlo-l, DFR-l were cloned . By inquiring GenBank. it's found that Mlo-1 was nearly same as barley Mlo in barley chromosome 411. so it may be the corresponding sequence of barley Mlo. OSMlo-l was over 98% indentity of corresponding sequences of OSMIo-hl. Though DFR-l was over 80% indentity of the corresponding sequence of rice DFR in some regions, there were some obvious different region between these two sequence, so it may be the corresponding sequence of the homologous gene of rice DFR By using Mapmaker/EXE3.0 software, DFR-I was mapped a position between molecular mark RG462 and R2635 in chromsome 1 using the cross of Zhenshan97B x Minghui63, and OSMlo-l was mapped a position 4.9 CM from molecular mark C751a in chromosome 6 using the population of Balilla/Dular//Naiijing11. According to Wang's (1994) study, these two fragments was mapped in regions containing two anti-blast QTLs. By RT-PCR, we found that DFR-l* corresponding with DFR-I cDNA expressed inceasingly in IRBB13's leaf inoculated with Xanthomanas orvzea pv oryzae race PXO99 and in Minghui63's leaf inoculated with Magnoparthe grisea race race V86013 . and OSMlo-l* corresponding with OSMIo-hl cDNA expressed in Minglmi63'leaf inoculated with V86013. It's suggested that the genes carrying DFR-I and OSMIo-l are very important in rice resistance reaction.