title: Gamma paleohexaploidy in the stem lineage of core eudicots: significance for MADS-box gene and species diversification.
abstract: Comparative genome biology has unveiled the polyploid origin of all angiosperms and the role of recurrent polyploidization in the amplification of gene families and the structuring of genomes. Which species share certain ancient polyploidy events, and which do not, is ill defined because of the limited number of sequenced genomes and transcriptomes and their uneven phylogenetic distribution. Previously, it has been suggested that most, but probably not all, of the eudicots have shared an ancient hexaploidy event, referred to as the gamma triplication. In this study, detailed phylogenies of subfamilies of MADS-box genes suggest that the gamma triplication has occurred before the divergence of Gunnerales but after the divergence of Buxales and Trochodendrales. Large-scale phylogenetic and K(S)-based approaches on the inflorescence transcriptomes of Gunnera manicata (Gunnerales) and Pachysandra terminalis (Buxales) provide further support for this placement, enabling us to position the gamma triplication in the stem lineage of the core eudicots. This triplication likely initiated the functional diversification of key regulators of reproductive development in the core eudicots, comprising 75% of flowering plants. Although it is possible that the gamma event triggered early core eudicot diversification, our dating estimates suggest that the event occurred early in the stem lineage, well before the rapid speciation of the earliest core eudicot lineages. The evolutionary significance of this paleopolyploidy event may thus rather lie in establishing a species lineage that was resilient to extinction, but with the genomic potential for later diversification. We consider that the traits generated from this potential characterize extant core eudicots both chemically and morphologically.
authors: Department of Biology, KULeuven, University of Leuven, Leuven, Belgium.
authors: Dries
authors: D
authors: Vekemans
authors: Sebastian
authors: S
authors: Proost
authors: Kevin
authors: K
authors: Vanneste
authors: Heleen
authors: H
authors: Coenen
authors: Tom
authors: T
authors: Viaene
authors: Philip
authors: P
authors: Ruelens
authors: Steven
authors: S
authors: Maere
authors: Yves
authors: Y
authors: Van de Peer
authors: Koen
authors: K
authors: Geuten
mesh_terms: D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D019143:Evolution, Molecular; D020869:Gene Expression Profiling; D018745:Genome, Plant / Q000235:genetics*; D056626:Inflorescence / Q000235:genetics / Q000378:metabolism; D016013:Likelihood Functions; D026161:MADS Domain Proteins / Q000235:genetics; D019684:Magnoliopsida / Q000235:genetics*; D008957:Models, Genetic; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics; D010802:Phylogeny; D011123:Polyploidy; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
chemical_list: D017931:DNA Primers; D026161:MADS Domain Proteins