Plant & Animal Genome V Conference
Town & Country Hotel, San Diego, CA, January 12-16, 1997.
PAG-V: W45 - R-GENE HOMOLOGUES AS CANDIDATES FOR CEREAL RESISTANCE GENES
W45
R-GENE HOMOLOGUES AS CANDIDATES FOR CEREAL RESISTANCE GENES
LEISTER, DARIO MICHAEL(1), Joachim Kurth(2), Masahiro Yano(3), Takuji Sasaki(3), David Laurie(3), Katrien Devos(3), Paul Schulze-Lefert(3)
1. Sainsbury Laboratory, John Innes Centre, NR4 7UH Norwich, U.K.
2. Sainsbury Laboratory, John Innes Centre, NR4 7UH Norwich, U.K
3. RGP,NIAR/STAFF, Tsukuba, Japan
R-gene homologues can be obtained by a PCR approach that uses degenerate primers to conserved domains of NBS-LRR type resistance genes. NBS-LRR type resistance genes were identified in Arabidopsis, tobacco, flax and the Solanacae. We conducted experiments to isolate these homologues by heterologous PCR from cereal genomes. Several primer sets were designed derived from two conserved domains of NBS-LRR type resistance genes. The primer sets were applied in PCR reactions with different templates (different species: rice and barley; genomic DNA of barley and cDNA of barley) and PCR products were cloned. A subsequent two-step-selection of cloned PCR products has been applied. This involved a selection for clones with an open reading frame and similarity of the deduced amino acid sequence to known NBS-LRR type R-genes. 17 clones exhibiting significant homology were isolated from the rice genome. We failed to amplify R-gene homologues from the complex barley genome by using genomic DNA as template. Only one R-gene homologue could be isolated from a barley leaf cDNA library. However, 9 barley homologues were isolated using RT-PCR and substractive procedures to enrich for low copy genomic barley DNA fragments prior to amplification with degenerate primers.Genome-wide mapping data of the rice R-gene homologues in rice revealed several correlations to mapped resistance traits and lesion mimic loci. Detailed map data will be presented and possible R-gene candidates will be described in detail.