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Thursday, August 3 • 15:20 - 15:40
Intragenic multiplications in diatom protein-coding genes

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Diatoms are unicellular algae belonging to the kindom Chromista, remarkable for their ability to create the species-specific siliceous cell wall. They have appeared circa 240 mya (Sorhannus 2007). Their genomes are usually 20-30 Mbp long and often include long non-coding insertions and short repeats (Vardi et al. 2010). A multiplication was recently shown the diatom silicon transporter (SIT) gene (Marchenkov et al. 2016). The aim of this work was to elucidate the scale of intragenic duplications in diatom genomes using our own as well as published genomic and transcriptomic sequences. We have used sequences of 31 diatom species in total; the analysis was performed with our own software pipeline. For the purposes of this work, the gene was considered multiplicated if and only if it has an analogue containing a single copy of the repetitive element, whether in the same organism or another. We have also excluded the genes rich in low-complexity regions that are also often repetitive, although with shorter repeat elements. It turned out that up to two percent of protein-coding genes detected in transcriptomic and genomic datasets used in this study contain multiplications corresponding to hundreds of aminoacids. Often the genes that encode this proteins are, quite literally, several copies of a protein sequence concatenated within a single ORF. For a comparison, we have searched for similar genes in other model eukaryotes. It turned out that less than a percent of Arabidopsis thaliana and Drosophila melanogaster genes fulfill these criteria, and none at all do for Saccharomyces cerevisiae. Distribution of multiplicated genes among diatoms suggests that these events did not happen simultaneously. It lead to the different repertoire of the repetitive genes among studied species. GO terms for most major functional groups and subcellular localisations are present in the multiplicated genes; membrane proteins are enriched, although they don't form a majority. We also should note that mRNA is transcribed from these genes, as evidenced by their presence in the transcriptomic datasets, which increases the copy number per single-copy element. It's probable that some of them are functional in the multicopy form, while others are processed. Thus, in this work we have, for the first time, estimated the scale of intragenic duplications within diatom protein-coding genes. It is higher than in other eukaryotes and varies between 0.8% and 2% protein-coding genes in different diatom species. This work was funded by the FASO projects #0345-2016-0005 and #0345-2015-0031


Thursday August 3, 2017 15:20 - 15:40
Graduate School of Management Building, room 309 Volkhovskiy Pereulok, 3, St. Petersburg, Russia

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