Investigating the role of gene duplication in the evolution and divergence of Arachnids

Gene duplication underlies the origin of novel genes with potential new functions that can contribute to organismal divergence. Relaxed selection on duplicates allows for the accumulation of mutations in coding and/or regulatory sequences of duplicated genes leading to subfunctionalization and/or neofunctionalization. Recent studies of spiders and scorpions have revealed a high prevalence of duplicated genes, including two Hox clusters and approximately 40% of other homeodomain containing genes. This supports the finding that there was a whole genome duplication (WGD) event in the common ancestor of these animals (Arachnopulmonata) that is not found in outgroups like ticks, mites and harvestmen. Studies of other known animal WGDs have shown how these events are often associated with an increase in organismal complexity, which is frequently linked to the diversification and functional divergence of entire gene families. To better understand the impact of this WGD event during arachnid evolution, I identified the homeobox and Sox gene repertoires of Phalangium opilio and compared the embryonic expression patterns of Sox and duplicated homeodomain genes in spiders, and their single copy orthologues in harvestmen. My results reveal striking patterns of sub and neofunctionalisation among ohnologs of homeodomain and Sox genes in spiders when compared to harvestmen. Taken together, my results suggest that the retention and subsequent divergence of ohnologs originated in the arachnopulmonate WGD likely contributed to the phenotypic diversification of this arachnid lineage. Additionally, to further our knowledge on spider embryogenesis and the genetic basis of phenotypic variation, I investigated the role of a duplicated SoxB gene (Pt-Sox21b-1) in spider segmentation, the role of Wnt signalling during spider eye development and the expression patterns of Pax6 and atonal duplicates in the developing head of P. tepidariorum. My results further support the role of Pt-Sox21b-1 as a gap gene in spider segmentation, and conserved roles for Wnt signalling and atonal in spider eye development, similar to those observed in Drosophila melanogaster.

Grantor dc:publisher

Oxford Brookes University

Year dc:date

2020

Author dc:creator

• Baudouin Gonzalez, Luís Miguel

Contributors dc:contributor

• McGregor, Alistair

Statement dc:rights

• All rights reserved

Language dc:language

en

DOI dc:identifier

https://doi.org/10.24384/gkzz-f690

OAI identifier oai:identifier

tle:0628a50b-5015-49e0-8002-ef08ad949ce1:d6bd9758-527a-46cd-bfe2-c433766e8fca:1