| Abstrakt: |
Forty-eight resistance (R) genes conferring resistance to various types of pests have been cloned from 12 plant species. Irrespective of the host or the pest type, most Rgenes share a strong protein sequence similarity especially for domains and motifs. The objective of this study was to identify expressed Rgenes of wheat, the fraction of which is expected to be very low in the genome. Using modified RNA fingerprinting and data mining approaches we identified 220 expressed R-gene candidates. Of these, 125 sequences structurally resembled known Rgenes. In addition to 25–87% protein sequence similarity with the known Rgenes, the sequence, order, and distribution of the domains and motifs were also the same. Among the remaining 95, 17 were probable R-related, 21 were a new class of nucleotide-binding kinases, 21 were probable kinases, and 36 were p-loop-containing unknown sequences. About 76% were rare including 73 novel sequences. Three new R-gene specific motifs were also identified. Physical mapping of the 164 best R-gene candidates on 339 deletion lines localized 121 mappable R-gene candidates to 26 small chromosomal regions encompassing about 16% of the genome. About 90 of the 110 phenotypically characterized wheat Rgenes corresponding to 18 different pests also mapped in these regions. |
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