The hAT-family transposable element, hopper, from Bactrocera dorsalis is a functional vector for insect germline transformation

Alfred M. Handler,Marc F. Schetelig

doi:10.1186/s12863-020-00942-3

Abstract

BackgroundThe hopper hAT-family transposable element isolated from the Oriental fruit fly, Bactrocera dorsalis, is distantly related to both the Drosophila hobo element and the Activator element from maize. The original 3120 bp hopperBd-Kah element isolated from the Kahuku wild-type strain was highly degenerate and appeared to have a mutated transposase and terminal sequences, while a second 3131 bp element, hopperBd-we, isolated from a white eye mutant strain had an intact transposase reading frame and terminal sequences consistent with function.ResultsThe hopperBd-we element was tested for function by its ability to mediate germline transformation in two dipteran species other than B. dorsalis. This was achieved by creating a binary vector/helper transformation system by linking the hopperBd-we transposase reading frame to a D. melanogaster hsp70 promoter for a heat-inducible transposase helper plasmid, and creating vectors marked with the D. melanogaster mini-white+ or polyubiquitin-regulated DsRed fluorescent protein markers.ConclusionsBoth vectors were successfully used to transform D. melanogaster, and the DsRed vector was also used to transform the Caribbean fruit fly, Anastrepha suspensa, indicating a wide range of hopper function in dipteran species and, potentially, non-dipteran species. This vector provides a new tool for insect genetic modification for both functional genomic analysis and the control of insect populations.

Highlights

The hopper hAT-family transposable element isolated from the Oriental fruit fly, Bactrocera dorsalis, is distantly related to both the Drosophila hobo element and the Activator element from maize
More than a decade passed before other Class II transposable elements were discovered that were functionally less restricted and successful in achieving non-drosophilid transformation, which included mariner/Mos1 discovered in D. mauritiana that initially transformed Aedes aegypti [4, 5], Minos discovered in D. hydei that initially transformed Ceratitis capitata [6, 7], piggyBac from the cabbage looper moth, Trichoplusia ni, that initially transformed C. capitata [8, 9], and the Hermes element found in Musca domestica [10] used initially to transform Ae. aegypti [11]
The marker insertion within the transposase coding region creates a nonautonomous vector that relies on an exogenous source of transposase for transposition, that was provided by the pUChsHopper helper plasmid having the transposase gene under D. melanogaster hsp70 promoter regulation for induction of expression by heat shock [17]

Summary

Introduction

The hopper hAT-family transposable element isolated from the Oriental fruit fly, Bactrocera dorsalis, is distantly related to both the Drosophila hobo element and the Activator element from maize. Results: The hopperBd-we element was tested for function by its ability to mediate germline transformation in two dipteran species other than B. dorsalis This was achieved by creating a binary vector/helper transformation system by linking the hopperBd-we transposase reading frame to a D. melanogaster hsp promoter for a heat-inducible transposase helper plasmid, and creating vectors marked with the D. melanogaster mini-white+ or polyubiquitinregulated DsRed fluorescent protein markers. Transposon-mediated germline transformation has been the primary method of insect genomic manipulation since a P element vector was successfully transposed into the Drosophila melanogaster genome [1]. Hermes is a member of the hobo, Activator, Tam (hAT) family of transposons that has been found to be phylogenetically widespread [12] While this supports the notion of widespread functionality, most full-length hAT elements (having a coding region and at least one terminal repeat sequence) were found to be defective, and far none, other than Hermes, have been shown to support insect transformation

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Conclusion