Legume genome evolution viewed through the Medicago truncatula and Lotus japonicus genomes.
Genome sequencing of the model legumes, Medicago truncatula and Lotus japonicus, provides an opportunity for large-scale sequence-based comparison of two genomes in the same plant family. Here we report synteny comparisons between these species, including details about chromosome relationships, large-scale synteny blocks, microsynteny within blocks, and genome regions lacking clear correspondence. The Lotus and Medicago genomes share a minimum of 10 large-scale synteny blocks, each with substantial collinearity and frequently extending the length of whole chromosome arms. The proportion of genes syntenic and collinear within each synteny block is relatively homogeneous. Medicago-Lotus comparisons also indicate similar and largely homogeneous gene densities, although gene-containing regions in Mt occupy 20-30% more space than Lj counterparts, primarily because of larger numbers of Mt retrotransposons. Because the interpretation of genome comparisons is complicated by large-scale genome duplications, we describe synteny, synonymous substitutions and phylogenetic analyses to identify and date a probable whole-genome duplication event. There is no direct evidence for any recent large-scale genome duplication in either Medicago or Lotus but instead a duplication predating speciation. Phylogenetic comparisons place this duplication within the Rosid I clade, clearly after the split between legumes and Salicaceae (poplar).
Cannon
Steven B
SB
Department of Plant Pathology, University of Minnesota, St. Paul, MN 55108, USA.
Sterck
Lieven
L
Rombauts
Stephane
S
Sato
Shusei
S
Cheung
Foo
F
Gouzy
Jérôme
J
Wang
Xiaohong
X
Mudge
Joann
J
Vasdewani
Jayprakash
J
Schiex
Thomas
T
Scheix
Thomas
T
Spannagl
Manuel
M
Monaghan
Erin
E
Nicholson
Christine
C
Humphray
Sean J
SJ
Schoof
Heiko
H
Mayer
Klaus F X
KF
Rogers
Jane
J
Quétier
Francis
F
Oldroyd
Giles E
GE
Debellé
Frédéric
F
Cook
Douglas R
DR
Retzel
Ernest F
EF
Roe
Bruce A
BA
Town
Christopher D
CD
Tabata
Satoshi
S
Van de Peer
Yves
Y
Young
Nevin D
ND
D032461:Chromosomes, Plant / Q000235:genetics; D020440:Gene Duplication; D017343:Genes, Plant / Q000235:genetics; D018745:Genome, Plant / Q000235:genetics*; D000070116:Lotus / Q000235:genetics*; D046913:Medicago truncatula / Q000235:genetics*; D010802:Phylogeny; D026801:Synteny / Q000235:genetics