The shibire^ts4 mutation causes temperature sensitive paralytic and lethal phenotypes in the Queensland fruit fly, Bactrocera tryoni

Bactrocera tryoni, the Queensland fruit fly, is among the most damaging insect pests to the Australian horticultural industry as larvae infest ripening fruits or vegetables prior to harvest. Genetic biocontrol using Sterile Insect Technique (SIT) programs have been used to successfully suppress populations, via mass release of factory-reared sterile males that mate with wild females. Bi-sex flies are currently used for releases, although the efficiency of these control programs could be improved through using genetic sexing strains that eliminate females early during development, as they are not required for SIT. Here we used CRISPR/Cas9 mutagenesis to modify two nucleotides in the B. tryoni gene shibire, which created a proline to serine amino acid substitution and produced a temperature sensitive phenotype. Shibire is an essential GTPase required in endocytosis and synaptic vesicle recycling, and classical mutagenic screens in the vinegar fly Drosophila melanogaster previously identified temperature sensitive alleles including shi^ts4 that results in adult paralysis. In B. tryoni, the shi^ts4 mutant strain exhibited similar adult paralytic phenotypes when exposed to high temperatures, as well as temperature dependent lethality at egg, larval and pupal stages when subjected to heat treatment above standard rearing temperatures. These temperature sensitive phenotypes could be adapted to develop a SIT genetic sexing strain for conditional elimination of females prior to sterile releases, to improve efficiency and reduce costs.