Microsynteny between the Medicago truncatula SYM2-orthologous genomic region and another region located on the same chromosome arm

Abstract

A synteny based positional cloning approach was started to clone the pea SYM2 gene by using locally conserved genome structure with the model plant Medicago truncatula. We reported that a pea marker tightly linked to SYM2 was used to screen a M. truncatula BAC library, and two contigs named C1/C2 and C3 were constructed that are both located on the long arm of M. truncatula chromosome 5 and separated by 9 cM. C1/C2 is highly microsyntenic to the pea SYM2 genomic region and corresponds to the M. truncatula SYM2-orthologous region, which is delimitated to 350 kbp. In this manuscript we analyze the distribution in the three contigs of 22 sequences and their homologues, including eight C1/C2 and two pea RFLP markers linked to SYM2. Among the analyzed sequences are several different (receptor) kinase-like gene sequences and two classes of LRR-containing resistance protein-like sequences. From all the studied sequences only four detected homologous sequences in C3, and their distribution is comparable in C1/C2 and C3, suggesting that a 70-kbp and a 120-kbp segments of these two contigs, respectively, arose through a duplication. The implications of these findings for the cloning of SYM2 are discussed.

Evolutionary, structural and functional relationships revealed by comparative analysis of syntenic genes in Rhizobiales

“…Species of Buchnera and Corynebacterium have low levels of chromosomal rearrangements and lack recA and recBCD orthologs, respectively [ 8 , 9 ], thus suggesting that recombination is an important factor for loss of synteny. Synteny studies have focused in short gene clusters in eukaryotes [ 10 , 11 ] while whole chromosome comparative analysis has been done in bacteria and archaea [ 12 - 18 ]. For example, there is a striking conservation between the chromosomes of Escherichia coli and Salmonella typhimurium [ 19 ], and also between those of Brucella melitensis, B. suis and Mesorhizobium loti [ 20 ].…”

Genome Exploitation

“…There is, however, evidence of gene duplication in Medicago; glutathione synthetase exists in two copies, most likely through a tandem duplication (Frendo et al, 2001). Additionally, Medicago chromosome 5 exhibits orthology with another region on the same chromosome showing evidence of segmental duplication (Gualtieri and Bisseling, 2002). It has been suggested that Medicago has a simple genome structure, with only tandem and segmental duplications (Kulikova et al, 2001).…”