Abstract
BackgroundAlthough gene overlapping is a common feature of prokaryote and mitochondria genomes, such genes have also been identified in many eukaryotes. The overlapping genes in eukaryotes are extensively rearranged even between closely related species. In this study, we investigated retention and rearrangement of positionally overlapping genes between the mosquitoes Aedes aegypti (dengue virus vector) and Anopheles gambiae (malaria vector). The overlapping gene pairs of A. aegypti were further compared with orthologs of other selected insects to conduct several hypothesis driven investigations relating to the evolution and rearrangement of overlapping genes.ResultsThe results show that as much as ~10% of the predicted genes of A. aegypti and A. gambiae are localized in positional overlapping manner. Furthermore, the study shows that differential abundance of introns and simple sequence repeats have significant association with positional rearrangement of overlapping genes between the two species. Gene expression analysis further suggests that antisense transcripts generated from the oppositely oriented overlapping genes are differentially regulated and may have important regulatory functions in these mosquitoes. Our data further shows that synonymous and non-synonymous mutations have differential but non-significant effect on overlapping localization of orthologous genes in other insect genomes.ConclusionGene overlapping in insects may be a species-specific evolutionary process as evident from non-dependency of gene overlapping with species phylogeny. Based on the results, our study suggests that overlapping genes may have played an important role in genome evolution of insects.
Highlights
Gene overlapping is a common feature of prokaryote and mitochondria genomes, such genes have been identified in many eukaryotes
Identification of overlapping genes A total of 761 and 565 overlapping gene pairs were identified in the assembled genomes of A. aegypti and A. gambiae, respectively (Additional file 1)
To determine if retention or rearrangement of overlapping localization of genes between A. aegypti and A. gambiae may be associated with loss or gain of terminal exons of genes, we investigated several gene pairs that contain multiple exons in the orthologous gene pairs (Additional file 3) and found no discrepancy in annotation of first and last exon of any gene pair between the two species
Summary
Gene overlapping is a common feature of prokaryote and mitochondria genomes, such genes have been identified in many eukaryotes. The overlapping genes in eukaryotes are extensively rearranged even between closely related species. Reshuffling of genomic DNA by gross chromosomal rearrangements generally involves a number of genes that undergo positional relocation in the genome. In addition to such large scale genomic rearrangements, genomic rearrangements at small scale levels facilitate relocation of genes which are otherwise positionally overlapping in a genome [5]. Studies show that overlapping genes in eukaryotes are extensively rearranged even between closely related species [5,12,14,15,16]. Several other insect genome sequences are available, overlapping genes of most of these insects have not been studied
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