A sequence-based genetic map of Medicago truncatula and comparison of marker colinearity with M. sativa.
A core genetic map of the legume Medicago truncatula has been established by analyzing the segregation of 288 sequence-characterized genetic markers in an F(2) population composed of 93 individuals. These molecular markers correspond to 141 ESTs, 80 BAC end sequence tags, and 67 resistance gene analogs, covering 513 cM. In the case of EST-based markers we used an intron-targeted marker strategy with primers designed to anneal in conserved exon regions and to amplify across intron regions. Polymorphisms were significantly more frequent in intron vs. exon regions, thus providing an efficient mechanism to map transcribed genes. Genetic and cytogenetic analysis produced eight well-resolved linkage groups, which have been previously correlated with eight chromosomes by means of FISH with mapped BAC clones. We anticipated that mapping of conserved coding regions would have utility for comparative mapping among legumes; thus 60 of the EST-based primer pairs were designed to amplify orthologous sequences across a range of legume species. As an initial test of this strategy, we used primers designed against M. truncatula exon sequences to rapidly map genes in M. sativa. The resulting comparative map, which includes 68 bridging markers, indicates that the two Medicago genomes are highly similar and establishes the basis for a Medicago composite map.
Choi
Hong-Kyu
HK
Department of Plant Pathology, University of California, Davis, California 95616, USA.
Kim
Dongjin
D
Uhm
Taesik
T
Limpens
Eric
E
Lim
Hyunju
H
Mun
Jeong-Hwan
JH
Kalo
Peter
P
Penmetsa
R Varma
RV
Seres
Andrea
A
Kulikova
Olga
O
Roe
Bruce A
BA
Bisseling
Ton
T
Kiss
Gyorgy B
GB
Cook
Douglas R
DR
D001483:Base Sequence; D002874:Chromosome Mapping; D022202:Chromosomes, Artificial, Bacterial; D032461:Chromosomes, Plant; D020732:Cytogenetic Analysis; D018744:DNA, Plant; D020224:Expressed Sequence Tags; D008040:Genetic Linkage; D005819:Genetic Markers; D018745:Genome, Plant; D017404:In Situ Hybridization, Fluorescence; D007438:Introns; D029902:Medicago / Q000235:genetics*; D000455:Medicago sativa / Q000235:genetics*; D011110:Polymorphism, Genetic; D014158:Transcription, Genetic
D018744:DNA, Plant; D005819:Genetic Markers