Submitted to: Genetics
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/4/2003
Publication Date: 10/1/2003
Citation: HUANG,L., BROOKS,S.A., LI,W., FELLERS,J.P., TRICK,H.N., GILL,B.S., MAP-BASED CLONING OF LEAF RUST RESISTANCE GENE LR21 FROM THE LARGE AND POLYPLOID GENOME OF BREAD WHEAT, GENETICS, 2003. 164:635-644. Interpretive Summary: Disease resistance to wheat leaf rust is usually controlled by a few genes with specific resistance to strains of fungi. This work describes the first leaf rust resistance gene to be cloned from wheat. Lr21 was cloned and verified by reinserting the gene into a susceptible cultivar. This work is important because it shows that genes can be cloned from wheat despite the large amount of DNA that it has, as well as multiple copies of most genes. This leaf rust resistance gene may be useful in reducing yield losses to leaf rust.
Technical Abstract: We report the map-based cloning of the leaf rust resistance gene Lr21, previously mapped to a gene-rich region at the distal end of chromosome arm 1DS of bread wheat (Triticum aestivum L.) Molecular cloning of Lr21 was facilitated by diploid/polyploid shuttle mapping strategy. Cloning of Lr21 was confirmed by genetic transformation and by stably inherited resistance phenotype in transgenic plants. Lr21 spans 4318 bp and encodes a 1080 amino acid protein containg a conserved nucleotide-binding site (NBS) domain, 13 imperfect leucine-rich repeats (LRRs), and a unique 151 amino acid sequence missing from known NBS-LRR proteins at the N terminus. Fine-structure genetic analysis at the Lr21 locus detected a noncrossover (recombination without exchange of flanking markers) within a 1415-bp region resulting from either a gene conversion tract of at least 191 bp or a double crossover. The successful map-based cloning approach as demonstrated here now opens the door for cloning of many crop-specific agronomic traits located in the gene-rich regions of bread wheat.