Pathogen-origin horizontally transferred genes contribute to the evolution of Lepidopteran insects

Zi-Wen Li,Zhong-Huai Xiang,Yi-Hong Shen,Ze Zhang

doi:10.1186/1471-2148-11-356

Abstract

BackgroundHorizontal gene transfer (HGT), a source of genetic variation, is generally considered to facilitate hosts' adaptability to environments. However, convincing evidence supporting the significant contribution of the transferred genes to the evolution of metazoan recipients is rare.ResultsIn this study, based on sequence data accumulated to date, we used a unified method consisting of similarity search and phylogenetic analysis to detect horizontally transferred genes (HTGs) between prokaryotes and five insect species including Drosophila melanogaster, Anopheles gambiae, Bombyx mori, Tribolium castaneum and Apis mellifera. Unexpectedly, the candidate HTGs were not detected in D. melanogaster, An. gambiae and T. castaneum, and 79 genes in Ap. mellifera sieved by the same method were considered as contamination based on other information. Consequently, 14 types of 22 HTGs were detected only in the silkworm. Additionally, 13 types of the detected silkworm HTGs share homologous sequences in species of other Lepidopteran superfamilies, suggesting that the majority of these HTGs were derived from ancient transfer events before the radiation of Ditrysia clade. On the basis of phylogenetic topologies and BLAST search results, donor bacteria of these genes were inferred, respectively. At least half of the predicted donor organisms may be entomopathogenic bacteria. The predicted biochemical functions of these genes include four categories: glycosyl hydrolase family, oxidoreductase family, amino acid metabolism, and others.ConclusionsThe products of HTGs detected in this study may take part in comprehensive physiological metabolism. These genes potentially contributed to functional innovation and adaptability of Lepidopteran hosts in their ancient lineages associated with the diversification of angiosperms. Importantly, our results imply that pathogens may be advantageous to the subsistence and prosperity of hosts through effective HGT events at a large evolutionary scale.

Highlights

Horizontal gene transfer (HGT), a source of genetic variation, is generally considered to facilitate hosts’ adaptability to environments
With the pipeline of similarity search and phylogenetic analysis, we found 22 silkworm genes and 79 honeybee genes that are the candidate horizontally transferred genes (HTGs) between insects and bacteria (Table 1)
Similarity search and phylogenetic analyses and other information were combined as a detection pipeline to reveal HGT event; this reduces the ratio of false positives

Summary

Introduction

Horizontal gene transfer (HGT), a source of genetic variation, is generally considered to facilitate hosts’ adaptability to environments. Case studies on HGT revealed that some of the transferred genes effectively participated in the biochemical metabolism and phenotypic divergence of multicellular eukaryotic hosts, implying that HGT may have biological importance in the functional evolution of metazoan recipients [8,18,19,20]. Convincing evidence supporting this issue is still lacking

Methods

Results

Discussion

Conclusion