Meeting Abstract
Horizontal gene transfer (HGT) is the transfer of genes from the genome of one species to that of another. HGT has been documented in several animal species, and recent work has suggested that HGT may have played an important role in the adaptive evolution of particular animal lineages. Despite the remarkability of HGT in animals, relatively little consideration has been paid to global patterns of function in animal HGTs. Likewise, the methodology behind HGT-detection in animals has not been analyzed in depth. Here we present alien_index, a program and database, which automates and standardizes identification of HGTs using established BLAST-based methods. We use alien_index to identify 37 new potential HGTs in the ctenophore (comb jelly) Mnemiopsis leidyi and apply phylogenetic and nucleotide-content analyses to support these predictions. All M. leidyi HGTs appear in the genomes and transcriptomes of two disparate populations ensuring that these genes are transcribed and unlikely to be contaminants. Furthermore, all M. leidyi HGTs are located on scaffolds with other intron-containing genes and 73% have introns. After casually observing a preponderance of enzymes represented in M. leidyi HGTs, we used alien_index to identify HGTs in the rotifer, tardigrade, and sponge genomes, and applied a Monte Carlo simulation approach (sampling well-annotated bacterial genomes) to see if enzyme representation was significantly different in these animal HGTs. Enzyme proportions in bacterial genomes significantly differed from animal HGTs, suggesting that there is preferential horizontal transmission of enzymes, or maintenance of enzymes after horizontal transmission. These results are the first to implicate horizontal gene transfer in ctenophores, and more generally, provide insight into how animals integrate alien genes into their genomes.
