An ancient genome duplication contributed to the abundance of metabolic genes in the moss Physcomitrella patens

Background: Analyses of complete genomes and large collections of gene transcripts have shown that most, if not all seed plants have undergone one or more genome duplications in their evolutionary past. Results: In this study, based on a large collection of EST sequences, we provide evidence that the haploid moss Physcomitrella patens is a paleopolyploid as well. Based on the construction of linearized phylogenetic trees we infer the genome duplication to have occurred between 30 and 60 million years ago. Gene Ontology and pathway association of the duplicated genes in P. patens reveal different biases of gene retention compared with seed plants. Conclusion: Metabolic genes seem to have been retained in excess following the genome duplication in P. patens. This might, at least partly, explain the versatility of metabolism, as described for P. patens and other mosses, in comparison to other land plants. Background In contrast to animals, the entire multicellular diploid generation of plants (along with the cuticle and thickwalled, non-motile spores) probably evolved after the transition to land [1,2]. All land plants display alternating multicellular generations – the sexual, haploid gametophyte and the asexual, diploid sporophyte. In early land plant fossils the gametophytic and sporophytic generation share about equal morphological complexity, making it likely that the gametophyte was reduced and the sporophyte became the dominant generation in vascular plants [1-3] while in “bryophytes” (mosses, hornworts and liverworts) the sporophyte generation was reduced and the gametophyte became dominant. Thus, “bryophytes” in comparison with vascular plants enable inference of early states of land plant evolution. Based upon spores found in the fossil record, the first plants had occupied the land in the Middle Ordovician, approximately 460 million years ago (MYA) [1]. The first splits among the Embryophyta separated the Bryopsida (mosses), Antocerotophyta (hornworts) and Marchantiophyta (liverworts) from the remainder of the land plants, the vascular plants. The oldest liverwort fossils are from the Late Devonian, ~360 MYA, the oldest mosses to be found in the fossil record are Published: 2 August 2007 BMC Evolutionary Biology 2007, 7:130 doi:10.1186/1471-2148-7-130 Received: 25 April 2007 Accepted: 2 August 2007 This article is available from: http://www.biomedcentral.com/1471-2148/7/130 © 2007 Rensing et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.