Comparative Analysis of Transposable Elements Reveals the Diversity of Transposable Elements in Decapoda and Their Effects on Genomic Evolution.

Transposable elements (TEs) are mobile genetic elements that exist in the host genome and exert considerable influence on the evolution of the host genome. Since crustaceans, including decapoda, are considered ideal models for studying the relationship between adaptive evolution and TEs, TEs were identified and classified in the genomes of eight decapoda species and one diplostraca species (as the outgroup) using two strategies, namely homology-based annotation and de novo annotation. The statistics and classification of TEs showed that their proportion in the genome and their taxonomic composition in decapoda were different. Moreover, correlation analysis and transcriptome data demonstrated that there were more PIF-Harbinger TEs in the genomes of Eriocheir sinensis and Scylla paramamosain, and the expression patterns of PIF-Harbingers were significantly altered under air exposure stress conditions. These results signaled that PIF-Harbingers expanded in the genome of E. sinensis and S. paramamosain and might be related to their air exposure tolerance levels. Meanwhile, sequence alignment revealed that some Jockey-like sequences (JLSs) with high similarity to specific regions of the White spot syndrome virus (WSSV) genome existed in all eight decapod species. At the same time, phylogenetic comparison exposed that the phylogenetic tree constructed by JLSs was not in agreement with that of the species tree, and the distribution of each branch was significantly different. The abovementioned results signaled that these WSSV-specific JLSs might transfer horizontally and contribute to the emergence of WSSV. This study accumulated data for expanding research on TEs in decapod species and also provided new insights and future direction for the breeding of stress-resistant and disease-resistant crab breeds.