Biology subjects

Wanninger, A.

Publications and source records attributed to Wanninger, A..

4 recordsLinked to original sources

bioRxiv2024

The genome of a sea spider corroborates a shared Hox cluster motif in arthropods with reduced posterior tagma

BackgroundChelicerate evolution is contentiously debated, with recent studies challenging traditional phylogenetic hypotheses and scenarios of major evolutionary events, like terrestrialization. Sea spiders (Pycnogonida) represent the uncontested marine sister group of all other chelicerates, featuring a - likely plesiomorphic - indirect development mode. Accordingly, pycnogonids hold the potential to provide crucial insight into early chelicerate genome evolution and ancestral principles of chelicerate body patterning. Leveraging this potential, however, has hitherto been hampered by the lack of high-quality genomic resources for pycnogonids. ResultsWe employed long-read sequencing and proximity ligation data to assemble the first near chromosome-level sea spider genome for Pycnogonum litorale, complemented by developmental transcriptomes and a high-fidelity Iso-Seq dataset. The assembly has a size of 471Mb in 57 pseudochromosomes, a repeat content of 61.05%, 15,497 predicted protein-coding genes, and is highly complete (95.8% BUSCO Arthropoda score, 95.7% of conserved microRNA families present). We identified a single, intact Hox gene cluster that lacks abdominal-A/Hox9, suggesting the loss of this Hox gene. ConclusionsOur high-quality genomic and transcriptomic resources establish P. litorale as a key research organism for modern studies on chelicerate genome evolution, development, and phylogeny. The presence of a single Hox cluster in the P. litorale genome further strengthens the inference that no whole-genome duplication occurred at the base of the chelicerate tree. The lack of abdA suggests that the combination of abdA loss and posterior tagmata reduction is a common theme in arthropod evolution, as it is shared with other, distantly related arthropod taxa with a vestigial opisthosoma/abdomen.

evolutionary biology↗

bioRxiv2020

The expanded plant-like mitogenome of the invasive quagga mussel, Dreissena rostriformis

BackgroundAnimal mitochondrial genomes are typically circular, 14-20 kb in length, maternally inherited, contain 13 coding genes, two ribosomal genes and are homoplasmic. In contrast, plant mitogenomes display frequent gene rearrangements, often contain greatly expanded repetitive regions, encode various open reading frames of unknown function and may be heteroplasmic due to differential repeat expansions between molecules. Error correction by recombination is common in plant mitochondria and has been proposed as the driver behind the rearrangements and repeat expansions that are often observed. In contrast, most animal mitochondria never or only very seldomly recombine and their utilisation of other repair mechanisms for mitochondrial genome error correction is a potential driver of their non-coding DNA reduction. ResultsUsing PacBio long reads for genome assembly and structural variant detection, we identify evidence of heteroplasmy in the form of variable repeat lengths within two blocks of repetitive DNA within the expanded 46 kb mitochondrial genome of the bivalve mollusc, quagga mussel, Dreissena rostriformis. The quagga mussel also has a greatly expanded repertoire of coding genes in comparison to most animals which includes an additional nine open reading frames (ORFs) encoding predicted transmembrane peptides of unknown orthology. ConclusionsThe genome size, repeat content and coding gene repertoire of the quagga mussel mitogenome closely resemble those of plants and the identification of repeat-associated heteroplasmy is consistent with the utilisation of plant-like recombination-based error correction mechanisms. Given the frequency of mitochondrial repeat expansions within the Bivalvia, recombination may be an underappreciated mechanism for mitogenomic error correction within this and other animal lineages. Significance StatementUnlike most animals, the mitochondrial genomes of many bivalve molluscs are often greatly expanded and contain large non-coding regions and additional predicted genes of unknown function. While these features are uncommon in other animal groups, they are common features of plant mitochondrial genomes. Here we show that the mitochondrial genome of the bivalve mollusc, the quagga mussel, displays many plant-like features and additionally, shows evidence of variability in the repeat lengths between mitochondrial molecules within an individual mussel. We propose that similar error correction mechanisms in plants and bivalves may play a role in these observed commonalities.

genomics↗

bioRxiv2018

The quagga mussel genome and the evolution of freshwater tolerance

European freshwater dreissenid mussels evolved from marine ancestors during the Miocene approximately 30 million years ago and today include some of the most successful and destructive invasive invertebrate species of temperate freshwater environments. Here we sequenced the genome of the quagga mussel Dreissena rostriformis to identify evolutionary adaptations involved in embryonic osmoregulation. We found high gene expression levels of a novel subfamily of lophotrochozoan-specific aquaporin water channel, a vacuolar ATPase and a sodium/hydrogen exchanger during early cleavage, a period defined by the formation of inter-cellular fluid-filled cleavage cavities. Independent expansions of the lophotrochoaquaporin clade that coincide with at least five independent colonisation events of freshwater environments confirm their central role in freshwater adaptation. The pattern of repeated aquaporin expansion and the evolution of membrane-bound fluid-filled osmoregulatory structures in diverse taxa points to a fundamental principle guiding the evolution of freshwater tolerance that may provide a framework for future efforts towards invasive species control.

genomics↗

bioRxiv2017

Neuronal Patterning Of The Tubular Collar Cord Is Highly Conserved Among Enteropneusts But Dissimilar To The Chordate Neural Tube

The dorsal neural tube of chordates and the ventral nerve cord of annelids exhibit a similar molecular mediolateral architecture. Accordingly, the presence of such a complex nervous system (CNS) has been proposed for their last common ancestor. Members of Enteropneusta, a group of non-chordate deuterostomes, possess a less complex CNS including a hollow neural tube, whereby homology to its chordate counterpart remains elusive. Since the majority of data on enteropneusts stem from Saccoglossus kowalevskii, a derived direct-developer, we investigated expression of key neuronal patterning genes in the indirect-developer Balanoglossus misakiensis.\n\nThe collar cord of B. misakiensis shows anterior Six3/6 and posterior Otx + engrailed expression, in a region corresponding to the chordate brain. Neuronal Nk2.1/Nk2.2 expression is absent. Interestingly, we found median Dlx and lateral Pax6 expression domains, i.e., a condition that is reversed compared to chordates.\n\nComparative analyses reveal that CNS patterning is highly conserved among enteropneusts. BmiDlx and BmiPax6 have no corresponding expression domains in the chordate brain, which may be indicative of independent acquisition of a tubular CNS in Enteropneusta and Chordata. Moreover, mediolateral architecture varies considerably among chordates and enteropneusts, questioning the presence of a vertebrate-like patterned nervous system in the last common deuterostome ancestor.

evolutionary biology↗