Characterization of a novel Helitron family in insect genomes: insights into classification, evolution and horizontal transfer

Authors: HAN, GUANGJIE - Yangzhou University; ZHANG, NAN - Yangzhou University; XU, JIAN - Yangzhou University; JIANG, HENG - Yangzhou University; JI, CAIHONG - Yangzhou University; ZHANG, ZE - Chongqing University; SONG, QISHENG - University Of Missouri; Stanley, David; FANG, JICHAO - Yangzhou University; WANG, JIANJUN - Yangzhou University

Submitted to: MOBILE DNA
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/30/2019
Publication Date: 5/31/2019
Citation: Han, G., Zhang, N., Xu, J., Jiang, H., Ji, C., Zhang, Z., Song, Q., Stanley, D.W., Fang, J., Wang, J. 2019. Characterization of a novel Helitron family in insect genomes: insights into classification, evolution and horizontal transfer. Mobile DNA. https://doi.org/10.1186/s13100-019-0165-4.
DOI: https://doi.org/10.1186/s13100-019-0165-4

Interpretive Summary: Chemical insecticides are effective pest insect management tools, however, negative effects, including environmental contamination and insect resistance to the insecticides attend use of these products. These negative effects drive research into alternative insect management technologies such as biological control based on deploying parasites and predators that consume pest insect species. More recently, novel pest control technologies are based on identification of key genes that can be targeted for disruption by gene-silencing technologies. Such pest control strategies raises important safety issues because some genes can move between species via several mechanisms. Here, we contribute more understanding of gene movements by reporting on a new family of genetic elements. This new information will be used by scientists working around the world develop effective and safe genetically-based insect pest control technologies.

Technical Abstract: Helitrons constitute a unique class of DNA transposons. Recent accelerated genome sequencing of insects has provided the opportunity to identify novel insect Helitrons. Here, we characterized a novel Helitron family discontinuously distributed in 27 out of 256 insect genomes. The most prominent characteristic of Hel1 family is its high sequence similarity among species of different insect orders. Related elements were also identified in two spiders, representing the first report of spider Helitrons. All these elements were classified into 2 families, 9 subfamilies and 35 exemplars based on our new classification criteria. These newly identified Helitrons were validated by in silico comparative analysis of insertion site polymorphism among multiple accessions. Autonomous partners of Helitron were reconstructed in the genomes of three insects including Cotesia vestalis, Papilio machaon and Athalia rosae as well as the spider Parasteatoda tepidariorum. Integration pattern analysis showed that majority of Hel1A elements in Papilio xuthus and Pieris rapae inserted into introns. Stepwise sequence acquisition was observed in Sfru_Hel1Aa, Sfru_Hel1Ab and Sfru_Hel1Ac in Spodoptera frugiperda. Remarkably, the evidence that Prap_Hel1Aa in a Lepidoptera insect, Pieris rapae, was derived from Cves_Hel1Aa in a parasitoid wasp, C. vestalis, suggested the role of nonregular host-parasite interactions in horizontal transfer (HT) of Helitrons. These findings provide new insights into the evolution and HT mechanisms of Helitrons.