Biology subjects

Woerheide, G.

Publications and source records attributed to Woerheide, G..

3 recordsLinked to original sources

bioRxiv2018

The role of homology and orthology in the phylogenomic analysis of metazoan gene content

Resolving animal (Metazoa) relationships is crucial to our understanding of, for example, the origin of their key traits such as muscles, guts and nerves. However, a broadly accepted metazoan consensus phylogeny has yet to emerge. In part this is because the genomes of deeply-diverging and fast-evolving lineages may undergo significant gene turnover, reducing the number of orthologs shared with related phyla. This can limit the usefulness of traditional phylogenetic methods that rely on alignments of orthologous sequences. Phylogenetic analysis of gene content has the potential to circumvent this orthology requirement, with binary presence/absence of homologous gene families representing a source of phylogenetically informative characters. Applying binary substitution models to the gene content of 26 complete animal genomes, we demonstrate that patterns of gene conservation differ markedly depending on whether gene families are defined by orthology or homology, i.e., whether paralogs are excluded or included. We conclude that the placement of deeply-diverging lineages, like ctenophores, may exceed the limit of resolution afforded by methods based on comparisons of orthologous protein supermatrices, and novel approaches are required to fully capture the evolutionary signal from genes within genomes.

evolutionary biology↗

bioRxiv2017

Divergence times in demosponges (Porifera): firstinsights from new mitogenomes and the inclusion offossils in a birth-death clock model

Approximately 80% of all recent sponge species belong to the class Demospongiae. Yet, despite their diversity and importance, accurate divergence times are still unknown for most demosponge clades. The estimation of demosponge divergence time is key to answering fundamental questions like e.g. the origin of Demospongiae, their diversification and historical biogeography. Molecular sequence data alone is not informative on an absolute time scale, and therefore needs to be \"calibrated\" with additional data such as fossils. Here, we apply the fossilized birth-death model (FBD), which has the advantage, compared to strict node dating with the oldest fossil occurrences, that it allows for the inclusion of young and old fossils in the analysis of divergence time. We use desma-bearing sponges, a diverse group of demosponges that form rigid skeletons and have a rich and continuous fossil record dating back to the Cambrian ([~]500 Ma), aiming to date the demosponge radiation and constrain the timing of key evolutionary events, like the transition from marine to freshwater habitats. To do so, we assembled mitochondrial genomes of six desma-bearing demosponges from size-selected reduced-representation genomic libraries and apply a fossilized birth-death model including 30 fossils and 33 complete demosponge mitochondrial genomes to infer a dated phylogeny of Demospongiae. Our study supports a Neoproterozoic origin of Demospongiae. Novel age estimates for the split of freshwater and marine sponges dating back to the Carboniferous and the previously assumed Recent ([~]18 Ma) diversification of freshwater sponges is supported. Moreover, we provide detailed age estimates for a possible diversification of Tetractinellidae ([~]315 Ma), the Astrophorina ([~]240 Ma), the Spirophorina ([~]120 Ma) and the family Corallistidae ([~]188 Ma) all of which are considered as key groups for dating the Demospongiae, due to their extraordinary rich and continuous fossil history.

evolutionary biology↗

bioRxiv2017

Mitochondrial RNA processing in absence of tRNApunctuations in octocorals

BackgroundMitogenome diversity is staggering among early branching animals with respect to size, gene density and content, gene orders, and number of tRNA genes, especially in cnidarians. This last point is of special interest as tRNA cleavage drives the maturation of mitochondrial mRNAs and is a primary mechanism for mt-RNA processing in animals. Mitochondrial RNA processing in non-bilaterian metazoans, some of which possess a single tRNA gene in their mitogenomes, is essentially unstudied despite its importance in understanding the evolution of mitochondrial transcription in animals.\n\nResultsWe characterized the mature mitochondrial mRNA transcripts in a species of the octocoral genus Sinularia (Alcyoniidae: Octocorallia), and defined precise boundaries of transcription units using different molecular methods. Most mt-mRNAs were polycistronic units containing two or three genes and 5 and/or 3 untranslated regions (UTRs) of varied length. The octocoral specific, mtDNA-encoded mismatch repair gene, mtMutS, was found to undergo alternative polyadenylation (APA), and exhibited differential expression of alternate transcripts suggesting a unique regulatory mechanism for this gene. In addition, a long noncoding RNA complementary to the ATP6 gene (lncATP6) potentially involved in antisense regulation was detected.\n\nConclusionsMt-mRNA processing in octocorals bearing a single mt-tRNA is complex. Considering the variety of mitogenome arrangements known in cnidarians, and in general among non-bilaterian metazoans, our findings provide a first glimpse into the complex mtDNA transcription, mt-mRNA processing, and regulation among early branching animals and represents a first step towards understanding its functional and evolutionary implications.

molecular biology↗