Rare whole genome duplication during spider evolution could reveal more about animal diversification

Monday, 31 July 2017

Parasteatoda-with-cocoon-800x450

Researchers, including scientists at Oxford Brookes University, have discovered a rare and ancient genomic change during the evolution of spiders and scorpions that could help us to understand more about the evolution of animals including humans.

Specifically, the discovery helps scientists understand how new copies of genes may contribute to animal diversification.

Analysis of the genome of the house spider, Parasteatoda tepidariorum, has revealed that spiders and scorpions evolved from an ancestor, over 400 million years ago, which made new copies of all of the genes in its genome – a process called whole genome duplication. 

Such an event is probably the largest evolutionary change that can happen to a genome and is relatively rare during animal evolution. However, there have also been two whole genome duplications at the origin of vertebrates, the lineage to which humans belong, fuelling long-standing debate about the role of these events in the diversification of vertebrate species. The new finding of a whole genome duplication in spiders and scorpions therefore provides a valuable comparison to the events in vertebrates and could help reveal genes and processes that have been important to our own evolution. 

Comparing the whole genome duplication in spiders and scorpions, with the independent events in vertebrates reveals a striking similarity – in both cases duplicated clusters of Hox genes have been retained. In all animals, these are very important genes that regulate development of body structures, and therefore can cause evolutionary changes in animal body plans.

Professor Alistair McGregor, Evolutionary Developmental Biology, Oxford Brookes University

Professor of Evolutionary Developmental Biology at Oxford Brookes University Alistair McGregor, lead author of the research, said: “While most of the new genetic material generated by whole genome duplication is subsequently lost, some of the new gene copies can evolve new functions and may contribute to the diversification of shape, size, physiology and behaviour of animals. 

“Comparing the whole genome duplication in spiders and scorpions, with the independent events in vertebrates reveals a striking similarity – in both cases duplicated clusters of Hox genes have been retained. In all animals, these are very important genes that regulate development of body structures, and therefore can cause evolutionary changes in animal body plans.”

The study also found that the copies of spider Hox genes show differences in when and where they are expressed, suggesting they have evolved new functions. 

Professor McGregor continued: “This suggests the retention of these genes has contributed to the diversification in both lineages.”

“In spiders and scorpions this event may help explain their evolutionary innovations including specialised limbs, how they breathe air, as well as the production of different types of venom and silk which spiders use to capture and kill their prey. 

“It will now be interesting to investigate the genomes of the relatives of spiders and scorpions to help pinpoint the duplicated genes involved in these innovations.”

The research paper, The house spider genome reveals an ancient whole-genome duplication during arachnid evolution, is published in the open-access journal BMC Biology. The paper can be viewed online.

Photo credit: Parasteatoda with cocoon,  Luca Livraghi