title: Genome comparisons reveal a dominant mechanism of chromosome number reduction in grasses and accelerated genome evolution in Triticeae.
abstract: Single-nucleotide polymorphism was used in the construction of an expressed sequence tag map of Aegilops tauschii, the diploid source of the wheat D genome. Comparisons of the map with the rice and sorghum genome sequences revealed 50 inversions and translocations; 2, 8, and 40 were assigned respectively to the rice, sorghum, and Ae. tauschii lineages, showing greatly accelerated genome evolution in the large Triticeae genomes. The reduction of the basic chromosome number from 12 to 7 in the Triticeae has taken place by a process during which an entire chromosome is inserted by its telomeres into a break in the centromeric region of another chromosome. The original centromere-telomere polarity of the chromosome arms is maintained in the new chromosome. An intrachromosomal telomere-telomere fusion resulting in a pericentric translocation of a chromosome segment or an entire arm accompanied or preceded the chromosome insertion in some instances. Insertional dysploidy has been recorded in three grass subfamilies and appears to be the dominant mechanism of basic chromosome number reduction in grasses. A total of 64% and 66% of Ae. tauschii genes were syntenic with sorghum and rice genes, respectively. Synteny was reduced in the vicinity of the termini of modern Ae. tauschii chromosomes but not in the vicinity of the ancient termini embedded in the Ae. tauschii chromosomes, suggesting that the dependence of synteny erosion on gene location along the centromere-telomere axis either evolved recently in the Triticeae phylogenetic lineage or its evolution was recently accelerated.
authors.affiliation: Department of Plant Sciences, University of California, Davis, CA 95616, USA.
authors.forename: M C
authors.initials: MC
authors.lastname: Luo
authors.forename: K R
authors.initials: KR
authors.lastname: Deal
authors.forename: E D
authors.initials: ED
authors.lastname: Akhunov
authors.forename: A R
authors.initials: AR
authors.lastname: Akhunova
authors.forename: O D
authors.initials: OD
authors.lastname: Anderson
authors.forename: J A
authors.initials: JA
authors.lastname: Anderson
authors.forename: N
authors.initials: N
authors.lastname: Blake
authors.forename: M T
authors.initials: MT
authors.lastname: Clegg
authors.forename: D
authors.initials: D
authors.lastname: Coleman-Derr
authors.forename: E J
authors.initials: EJ
authors.lastname: Conley
authors.forename: C C
authors.initials: CC
authors.lastname: Crossman
authors.forename: J
authors.initials: J
authors.lastname: Dubcovsky
authors.forename: B S
authors.initials: BS
authors.lastname: Gill
authors.forename: Y Q
authors.initials: YQ
authors.lastname: Gu
authors.forename: J
authors.initials: J
authors.lastname: Hadam
authors.forename: H Y
authors.initials: HY
authors.lastname: Heo
authors.forename: N
authors.initials: N
authors.lastname: Huo
authors.forename: G
authors.initials: G
authors.lastname: Lazo
authors.forename: Y
authors.initials: Y
authors.lastname: Ma
authors.forename: D E
authors.initials: DE
authors.lastname: Matthews
authors.forename: P E
authors.initials: PE
authors.lastname: McGuire
authors.forename: P L
authors.initials: PL
authors.lastname: Morrell
authors.forename: C O
authors.initials: CO
authors.lastname: Qualset
authors.forename: J
authors.initials: J
authors.lastname: Renfro
authors.forename: D
authors.initials: D
authors.lastname: Tabanao
authors.forename: L E
authors.initials: LE
authors.lastname: Talbert
authors.forename: C
authors.initials: C
authors.lastname: Tian
authors.forename: D M
authors.initials: DM
authors.lastname: Toleno
authors.forename: M L
authors.initials: ML
authors.lastname: Warburton
authors.forename: F M
authors.initials: FM
authors.lastname: You
authors.forename: W
authors.initials: W
authors.lastname: Zhang
authors.forename: J
authors.initials: J
authors.lastname: Dvorak
mesh_terms: D002503:Centromere / Q000235:genetics; D007446:Chromosome Inversion; D002874:Chromosome Mapping; D032461:Chromosomes, Plant / Q000235:genetics; D019143:Evolution, Molecular; D020224:Expressed Sequence Tags; D018745:Genome, Plant; D008957:Models, Genetic; D012275:Oryza / Q000235:genetics; D010802:Phylogeny; D006109:Poaceae / Q000145:classification / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide; D045868:Sorghum / Q000235:genetics; D013045:Species Specificity; D026801:Synteny; D016615:Telomere / Q000235:genetics; D014178:Translocation, Genetic; D014908:Triticum / Q000235:genetics