title: Map-based cloning of leaf rust resistance gene Lr21 from the large and polyploid genome of bread wheat.
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 a stably inherited resistance phenotype in transgenic plants. Lr21 spans 4318 bp and encodes a 1080-amino-acid protein containing 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.
authors.affiliation: Wheat Genetics Resource Center, Department of Plant Pathology, Kansas State University, Manhattan 66506-5502, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Huang
authors.forename: Steven A
authors.initials: SA
authors.lastname: Brooks
authors.forename: Wanlong
authors.initials: W
authors.lastname: Li
authors.forename: John P
authors.initials: JP
authors.lastname: Fellers
authors.forename: Harold N
authors.initials: HN
authors.lastname: Trick
authors.forename: Bikram S
authors.initials: BS
authors.lastname: Gill
mesh_terms: D015139:Blotting, Southern; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D003360:Cosmids / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D015723:Gene Library; D005816:Genetic Complementation Test; D020022:Genetic Predisposition to Disease; D018745:Genome, Plant; D007930:Leucine / Q000737:chemistry; D008957:Models, Genetic; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010641:Phenotype; D010935:Plant Diseases / Q000235:genetics*; D030821:Plants, Genetically Modified; D017434:Protein Structure, Tertiary; D011995:Recombination, Genetic; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016324:Sequence Tagged Sites; D014908:Triticum / Q000235:genetics*
chemical_list: D018076:DNA, Complementary; D007930:Leucine