The abundance and widespread distribution of transposable elements required a unified classification to divide these sequences into different lineages though it is still a subject of debate 11– 13. Transposable elements comprised a considerable proportion of eukaryotic and prokaryotic genome 9, e.g., approximately 3–20% of the genomes in many filamentous fungi 10, 10%, 12%, 37%, 45% and 80% of the genome in fish, Caenorhabditis elegans, mouse, human and some plants, respectively 2, 3. Although the recent advancements to the understanding of TE evolution, there are still considerable gaps of knowledge to completely understand the evolutionary interplay between host and genomic parasites 8, 9. The complexity and paraphyletic origin of TEs poses substantial challenges to the scientific community, including the detection, classification, assembly, annotations and mapping of genomic variants 8. The influence of TEs on genome organization and evolution is not surprising and enough information is available about impact of TEs in the host genome evolution. Moreover, TEs have the ability to modify the expression of their host genes by juxtaposing new cis-regulatory sequences, and can also be co-opted to new host function and give rise to new host genes 3– 6, through a phenomenon known as molecular domestication 7. During transposition, they may disrupt coding or regulatory sequences, and the high similar copies, which dispersed in the genome, can serve as source of non-homologous recombination breaking points resulting in chromosomal rearrangement such as inversion, deletion, translocation, and duplication. However, very small proportion of TE sequences are currently active with intact open reading frame (ORF) for transposase and most have many deletions and substitution due to vertical inactivation events by the host, and hence they are the inactive remains of once active copies 4. Transposable elements have considerable influence on the evolution of host genome due to their propagation and replication within host genome 3. Once these elements exploit the host cellular machinery for their own replication, they may have a large negative impact on the host fitness 1– 3. Transposable elements (TEs) are DNA sequences (usually less than 15 kb), which have the ability to jump and change its location within the genome, also known as genomic parasites 1, 2. Our present report revealed the diversity and distribution of MLEs in Rhus gall aphid genomes and expanded our understandings on the characterization of transposable elements in aphid genomes, which might be useful as genetic markers and tools and would play an important role in genomic evolution and adaptation of aphids. Phylogenetic analysis showed that all the 121 MLE sequences belonged to four subfamilies, i.e., Mauritiana, Drosophila, Vertumana and Irritans, among which Drosophila and Vertumana subfamilies were reported in aphids for the first time. The sequences of MLEs ranged from 1 to 1.4 kb in length and the structural analysis of the MLEs showed that only five copies were potentially active with intact open reading frame (ORF) and terminal inverted repeats ( TIRs). In total, 121 MLEs were detected in the genomes of the seven investigated species of Rhus gall aphids, which showed a wide distribution in both close and distant related species. Mariner like elements (MLEs) were searched in the genomes of seven species of Rhus gall aphids belonging to six genera. Mariner/DD34D family belongs to class II transposable elements which is widely spread in the genomes of insects and have considerable role in genomic evolution. Transposable elements (TEs), also known as jumping genes, are widely spread in the genomes of insects and play a considerable role in genomic evolution.
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