title: Polyploid evolution of the Brassicaceae during the Cenozoic era.
abstract: The Brassicaceae (Cruciferae) family, owing to its remarkable species, genetic, and physiological diversity as well as its significant economic potential, has become a model for polyploidy and evolutionary studies. Utilizing extensive transcriptome pyrosequencing of diverse taxa, we established a resolved phylogeny of a subset of crucifer species. We elucidated the frequency, age, and phylogenetic position of polyploidy and lineage separation events that have marked the evolutionary history of the Brassicaceae. Besides the well-known ancient α (47 million years ago [Mya]) and β (124 Mya) paleopolyploidy events, several species were shown to have undergone a further more recent (∼7 to 12 Mya) round of genome multiplication. We identified eight whole-genome duplications corresponding to at least five independent neo/mesopolyploidy events. Although the Brassicaceae family evolved from other eudicots at the beginning of the Cenozoic era of the Earth (60 Mya), major diversification occurred only during the Neogene period (0 to 23 Mya). Remarkably, the widespread species divergence, major polyploidy, and lineage separation events during Brassicaceae evolution are clustered in time around epoch transitions characterized by prolonged unstable climatic conditions. The synchronized diversification of Brassicaceae species suggests that polyploid events may have conferred higher adaptability and increased tolerance toward the drastically changing global environment, thus facilitating species radiation.
authors.affiliation: Agriculture and Agri-Food Canada, Saskatoon SK S7N 0X2, Canada National Research Council Canada, Saskatoon SK S7N 0W9, Canada.
authors.forename: Sateesh
authors.initials: S
authors.lastname: Kagale
authors.affiliation: Agriculture and Agri-Food Canada, Saskatoon SK S7N 0X2, Canada.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Robinson
authors.affiliation: Agriculture and Agri-Food Canada, Saskatoon SK S7N 0X2, Canada.
authors.forename: John
authors.initials: J
authors.lastname: Nixon
authors.affiliation: Agriculture and Agri-Food Canada, Saskatoon SK S7N 0X2, Canada.
authors.forename: Rong
authors.initials: R
authors.lastname: Xiao
authors.affiliation: Agriculture and Agri-Food Canada, Saskatoon SK S7N 0X2, Canada.
authors.forename: Terry
authors.initials: T
authors.lastname: Huebert
authors.affiliation: National Research Council Canada, Saskatoon SK S7N 0W9, Canada.
authors.forename: Janet
authors.initials: J
authors.lastname: Condie
authors.affiliation: Plant Gene Resources of Canada, Saskatoon SK S7N 0X2, Canada.
authors.forename: Dallas
authors.initials: D
authors.lastname: Kessler
authors.affiliation: Agriculture and Agri-Food Canada, Saskatoon SK S7N 0X2, Canada.
authors.forename: Wayne E
authors.initials: WE
authors.lastname: Clarke
authors.affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, California 94720.
authors.forename: Patrick P
authors.initials: PP
authors.lastname: Edger
authors.affiliation: Agriculture and Agri-Food Canada, Saskatoon SK S7N 0X2, Canada.
authors.forename: Matthew G
authors.initials: MG
authors.lastname: Links
authors.affiliation: National Research Council Canada, Saskatoon SK S7N 0W9, Canada.
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Sharpe
authors.affiliation: Agriculture and Agri-Food Canada, Saskatoon SK S7N 0X2, Canada isobel.parkin@agr.gc.ca.
authors.forename: Isobel A P
authors.initials: IA
authors.lastname: Parkin
mesh_terms: D001483:Base Sequence; D019607:Brassicaceae / Q000145:classification / Q000235:genetics*; D031485:Cleome / Q000145:classification / Q000235:genetics*; D019143:Evolution, Molecular; D015723:Gene Library; D018745:Genome, Plant / Q000235:genetics*; D059014:High-Throughput Nucleotide Sequencing; D058977:Molecular Sequence Annotation; D008969:Molecular Sequence Data; D010802:Phylogeny; D018515:Plant Leaves / Q000145:classification / Q000235:genetics; D011123:Polyploidy; D012333:RNA, Messenger / Q000235:genetics; D018749:RNA, Plant / Q000737:chemistry / Q000235:genetics; D017422:Sequence Analysis, DNA; D013997:Time Factors; D059467:Transcriptome
chemical_list: D012333:RNA, Messenger; D018749:RNA, Plant