An integrated physical, genetic and cytogenetic map around the sunn locus of Medicago truncatula.
The sunn mutation of Medicago truncatula is a single-gene mutation that confers a novel supernodulation phenotype in response to inoculation with Sinorhizobium meliloti. We took advantage of the publicly available codominant PCR markers, the high-density genetic map, and a linked cytogenetic map to define the physical and genetic region containing sunn. We determined that sunn is located at the bottom of linkage group 4, where a fine-structure genetic map was used to place the locus within a approximately 400-kb contig of bacterial artificial chromosome (BAC) clones. Genetic analyses of the sunn contig, as well as of a second, closely linked BAC contig designated NUM1, indicate that the physical to genetic distance within this chromosome region is in the range of 1000 -1100 kb.cM-1. The ratio of genetic to cytogenetic distance determined across the entire region is 0.3 cM.microm(-1). These estimates are in good agreement with the empirically determined value of approximately 300 kb.microm(-1) measured for the NUM1 contig. The assignment of sunn to a defined physical interval should provide a basis for sequencing and ultimately cloning the responsible gene.
Schnabel
E
E
Department of Genetic and Biochemistry, Clemson University, Clemson, SC USA. ffrugol@clemson.edu
Kulikova
O
O
Penmetsa
R V
RV
Bisseling
T
T
Cook
D R
DR
Frugoli
J
J
D016386:Chromosome Walking; D017404:In Situ Hybridization, Fluorescence; D029902:Medicago / Q000235:genetics*; D020161:Physical Chromosome Mapping