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Evolutionary Genetics and/or Genomics Vandewege, Michael W [1]. Variable targeting of transposable elements by piRNA/PIWI proteins in two Laurasiatherians. Transposable elements(TEs) are discrete DNA sequences that have the unique ability to mobilize or duplicate themselves within a genome. In mammals, TEs account for 20-50% of the genomic content. TE mobilization can have significant, potentially deleterious genomic impacts that can lead to genetic diseases. TEs can be classified as either DNA transposons which use a âcut and pasteâ, or retrotransposons that use âcopy and pasteâ mechanism. Mammalian TE activity can vary greatly among species.
PIWI proteins are generally expressed in the germ line, are proposed as defenders of the genome against TE proliferation in animals, and use small RNAs (piRNAs) as guides to identify complementary regions in RNA transcripts. piRNAs are small RNA molecules usually between 24 and 32 bp long. Research has shown many piRNA sequences are derived from TEs and play a role in TE silencing.
We explored how piRNA targeting of TEs differ in two mammals under different TE stresses from an evolutionary perspective. The dog and horse tolerate differential TE stresses.Only 100 completely intact, putatively active L1s have been described from the horse genome, whereas L1 and SINE retrotransposon are expanding in the dog genome. We sought to explore whether piRNAs target TEs in either of these organisms, if piRNAs show any age bias of targeted TEs, and to detect piRNA targeting bias between the dog and horse elements given their differences in TE activity.
Retrotransposon derived piRNAs combined represented 26 (dog) and 32% (horse) of uniquely mapping piRNAs. When we recorded all of the possible alignment positions of piRNAs in the retrotransposons, we found approximately 60% of TE derived piRNA were from LINEs in the dog vs. 28% in the horse and we found the inverse for SINEs. We found that 60% of possible TE derived piRNA were from SINEs, though SINE activity has been declining. We further by determining an age bias, and we observed a general trend where younger LINE and SINE families had higher piRNA densities. When we compared LINE families of the dog and horse, it was clear younger LINE families in the dog had higher piRNA densities than the horse LINE families, yet horse SINE families had higher piRNA densities than in the dog.
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1 - Mississippi State University, Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, 32 Creelman St, Mississippi State , MS, 39762, USA
Keywords:
piRNA
transposable elements
gene silencing
genomics
small RNA.
Presentation Type: Regular Oral Presentation
Session: 61
Location: Cotton D/Snowbird Center
Date: Sunday, June 23rd, 2013
Time: 11:15 AM
Number: 61004
Abstract ID:1161
Candidate for Awards:W.D. Hamilton Award for Outstanding Student Presentation |
