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Molecular evolution of visual pigments in the wandering spider Cupiennius salei
Animals absorb light with proteins called opsins, and having a suite of opsins absorbing light at different wavelengths allows for colour vision. Three opsins were recently identified in jumping spiders, and during my placement project at the University of Vienna, I set out to isolate and characterise homologs to these in another species, Cupiennius salei. A homolog for the Rh2 gene was identified, and one section in the middle showed a remarkable diversity in its genetic make-up, suggesting multiple gene duplication events, with possible functional divergence (i.e. different versions of the same gene would be able to absorb light across a broad spectrum).Two possible explanations are that either different DNA sequences are the result of gene conversion events, whereby sections of gene are accidentally swapped or copied within the cell nucleus, or alternative splicing, whereby the building blocks of the protein are assembled in different orders.
I am hoping to build on my work in Austria by analysing the structural diversity of the protein across a much broader sequence to give a more accurate picture of the phylogenetic history of the gene. This will involve both statistical analyses to test for possible functional divergence and 3D modelling of the protein to examine the protein structure in space. Furthermore, I intend to examine the so-called ‘untranslated region’, the section of the the gene which does not actually reflected in the protein, which will elucidate possible gene conversion and alternative splicing events.
The grand pattern of invertebrate opsin evolution is one of repeated duplication and deletion. C. salei seems to provide a striking example of this pattern; (at least) one long-wave opsin seems to have been lost, whilst one seems to have multiplied many times to take its place. Furthermore, data on spiders and their relatives are currently severely lacking, so as well as filling in a large gap in the evolutionary tree, work such as this can also help resolve issues regarding the overall relatedness of groups such as arachnids and millipedes/centipedes.
Project Team: Thomas Ellis Faculty: Life Sciences and Humanities
Funding year: 2009
Keywords: undergraduate research spiders opsins light animals absorption
