title: Refuting the hypothesis that the acquisition of germ plasm accelerates animal evolution.
abstract: Primordial germ cells (PGCs) give rise to the germ line in animals. PGCs are specified during embryogenesis either by an ancestral mechanism of cell-cell signalling (induction) or by a derived mechanism of maternally provided germ plasm (preformation). Recently, a hypothesis was set forth purporting that germ plasm liberates selective constraint and accelerates an organism's protein sequence evolution, especially for genes from early developmental stages, thereby leading to animal species radiations; empirical validation has been claimed in vertebrates. Here we present findings from global rates of protein evolution in vertebrates and invertebrates refuting this hypothesis. Contrary to assertions of the hypothesis, we find no effect of preformation on protein sequence evolution, the evolutionary rates of early-stage developmental genes, or on species diversification. We conclude that the hypothesis is mechanistically implausible, and our multi-faceted analysis shows no empirical support for any of its predictions.
authors: Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Avenue, Cambridge, Massachusetts 02138, USA.
authors: Carrie A
authors: CA
authors: Whittle
authors: Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Avenue, Cambridge, Massachusetts 02138, USA.|Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, Massachusetts 02138, USA.
authors: Cassandra G
authors: CG
authors: Extavour
mesh_terms: D000818:Animals; D002450:Cell Communication / Q000502:physiology; D003593:Cytoplasm / Q000502:physiology*; D047108:Embryonic Development / Q000502:physiology; D019143:Evolution, Molecular; D020869:Gene Expression Profiling; D049810:Genetic Speciation; D023281:Genomics; D005854:Germ Cells / Q000502:physiology*; D007448:Invertebrates / Q000196:embryology / Q000502:physiology*; D016415:Sequence Alignment; D013997:Time Factors; D014714:Vertebrates / Q000196:embryology / Q000502:physiology*