The hAT-family hopper transposon exists as highly similar yet discontinuous elements in the Bactrocera tephritid fly genus

Authors: Handler, Alfred - Al; Furlong, Richard

Submitted to: Insect Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/23/2023
Publication Date: 1/22/2024
Citation: Handler, A.M., Furlong, R.B. 2024. The hAT-family hopper transposon exists as highly similar yet discontinuous elements in the Bactrocera tephritid fly genus. Insect Molecular Biology. 33(1):1-10. https://doi.org/10.1111/imb.12891.
DOI: https://doi.org/10.1111/imb.12891

Interpretive Summary: Transposable elements exist in most organisms and since they create mutations, they are a driving force in evolution, and as mobile elements they have been modified for use in the gene transfer of recombinant DNA for genetic modifications. To expand our ability to genetically modify tephritid fruit fly pest insects, and to also understand the evolutionary relationships of these species, we previously isolated the hopper transposon from the Oriental fruit fly. To further understand the presence and relationships of hopper elements in this fruit fly and related species, scientists at the USDA-ARS in Gainesville, Florida surveyed the genome of nine Bactrocera species and strains for both intact mobile hopper elements and mutated non-mobile elements. Non-functional elements, that descended from a functional element, were discovered in all species except one, and a possible functional element was discovered in one of these species. This knowledge will help guide the use of hopper as a vector for genetic modification of strains useful for the sterile insect technique, in addition to understanding the evolution of tephritid fruit flies.

Technical Abstract: The hAT-family hopper transposable element was originally discovered as a defective element in a Bactrocera dorsalis wild type strain, and subsequently a functional element, hopperBdwe, was isolated from a white eye mutant strain. The latter study showed that closely related elements existed in the distantly related melonfly, Zeugodacus cucurbitae, suggesting that hopper could have a widespread presence in the Bactrocera genus. To further understand the distribution of hopper within and beyond the B. dorsalis species complex, primer pairs from hopper-Bdwe and its adjacent genomic insertion site were used to survey the presence and relatedness of hopper in five species within the complex and four species outside the complex. Based on sequence identity of a 1.94 kb internal nucleotide sequence, the closest relationships were with defective elements from B. dorsalis s.s. and species synonymized with B. dorsalis including B. papayae, B. philipiensis, and B. invadens, ranging in identity between 88.4% to 99.5%. Notably, B. carambolae, which is most closely related to B. dorsalis beyond the synonymized species, shared hopper identities of 97.3% to 99.4%. Beyond the B. dorsalis complex, Zeugodacus cucurbitae, B. tryoni and B. zonata shared identities of 83.1% to 97.1%, however, hopper was absent from B. oleae. While the functional autonomous hopperBdwe element was not detected in these species, another hopper element isolated from B. dorsalis has an uninterrupted transposase open reading frame. The discontinuous presence of hopper in the Bactrocera genus has implications for its use for genomic manipulation and understanding the phylogenetic relationship of these species.