Horizontal transfer and subsequent explosive expansion of a DNA transposon in sea kraits (Laticauda).

James D Galbraith,Alexander Suh,Kate L Sanders,Alastair J Ludington,David L Adelson

doi:10.1098/rsbl.2021.0342

James D Galbraith, Alexander Suh + Show 3 more

Open Access

https://doi.org/10.1098/rsbl.2021.0342

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Abstract

Transposable elements (TEs) are self-replicating genetic sequences and are often described as important ‘drivers of evolution’. This driving force is because TEs promote genomic novelty by enabling rearrangement, and through exaptation as coding and regulatory elements. However, most TE insertions potentially lead to neutral or harmful outcomes, therefore host genomes have evolved machinery to suppress TE expansion. Through horizontal transposon transfer (HTT) TEs can colonize new genomes, and since new hosts may not be able to regulate subsequent replication, these TEs may proliferate rapidly. Here, we describe HTT of the Harbinger-Snek DNA transposon into sea kraits (Laticauda), and its subsequent explosive expansion within Laticauda genomes. This HTT occurred following the divergence of Laticauda from terrestrial Australian elapids approximately 15–25 Mya. This has resulted in numerous insertions into introns and regulatory regions, with some insertions into exons which appear to have altered UTRs or added sequence to coding exons. Harbinger-Snek has rapidly expanded to make up 8–12% of Laticauda spp. genomes; this is the fastest known expansion of TEs in amniotes following HTT. Genomic changes caused by this rapid expansion may have contributed to adaptation to the amphibious-marine habitat.

Highlights

Transposable elements (TEs) are self-replicating genetic elements that mobilize themselves across genomes
In addition to being vertically inherited, TEs can invade a new host through horizontal transposon transfer (HTT)
We describe the rapid expansions of HarbingerSnek TEs in Laticauda spp., which is to our knowledge, the fastest expansion of a DNA transposon in amniotes reported to date

Summary

Introduction

Transposable elements (TEs) are self-replicating genetic elements that mobilize themselves across genomes. We report the HTT of a Harbinger DNA transposon, Harbinger-Snek, into Laticauda, a genus of marine snakes which diverged from terrestrial Australian snakes 15–25 Mya [19,20,21]. Due to the absence of Harbinger-Snek-like sequences from terrestrial species and highly similar sequences present in marine species, we propose Harbinger-Snek was horizontally transferred to Laticauda from a marine donor genome during habitat transition. Since this initial HTT event, Harbinger-Snek has expanded rapidly within the genomes of Laticauda and accounts for 8% of the L. laticaudata assembly and 12% of the L. colubrina assembly

Methods

Conclusion

El Baidouri M et al 2014 Widespread and frequent

15. Chen L et al 2019 Large-scale ruminant genome

Findings

57. Pasquesi GIM et al 2018 Squamate reptiles