Structural variations generated by simian foamy virus-like (SFV) in Crocodylus siamensis

Abstract

Endogenous retrovirus (ERV) integrates into the germline of its host and could remain in the genome as a molecular fossil. ERV is one of sources that cause INDEL and recombination events in the vertebrate genomes, leading to various genomic and genetic changes in their hosts. There have been many studies conducted on ERVs in the vertebrate genomes to elucidate their evolutionary history. However, ERVs have not been studied well in Crocodylus siamensis. Here, we report structural variations among SFV1 elements (simian foamy virus-like), ERVs in C. siamensis. We initially identified 26 SFV1 candidates in the genome and experimentally verified 9 SFV1_1 and 5 SFV1_10 elements using PCR display. Their structural analyses showed that most of them are solitary-LTRs but two SFV1_1 elements are full-length. Through further analyses, we found that the two full-length elements retain intact ORFs. We examined transcription factor binding sites within their LTR sequences to predict promoter/enhancer activities. In sum, we identified 14 crocodile-specific SFV1 elements and the results of their structural analyses suggest that they could contribute to genomic or phenotypic variations in C. siamensis population.

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