Development and testing of a novel Killer-Rescue self-limiting gene drive system in Drosophila melanogaster

Abstract

We report the development and laboratory testing of a novel Killer-Rescue (K-R) self-limiting gene drive system in Drosophila melanogaster. This K-R system utilizes the well-characterized Gal4/UAS binary expression system and the Gal4 inhibitor, Gal80. Three killer (K) lines were tested; these used either an autoregulated UAS-Gal4 or UAS-Gal4 plus UAS-hid transgene. One universal rescue (R) line was used, UAS-Gal80, to inhibit Gal4 expression. The K lines are lethal and cause death in the absence of R. We show that Gal4 RNA levels are high in the absence of R. Death is possibly due to transcriptional squelching from high levels of Gal4. When R is present, Gal4 activation of Gal80 would lead to inhibition of Gal4 and prevent overexpression. With a single release ratio of 2:1 engineered K-R to wildtype, we find that K drives R through the population while the percent of wild type individuals decreases each generation. The choice of core promoter for a UAS-Gal4 construct strongly influences the K-R system. With the strong hsp70 core promoter, K was very effective but was quickly lost from the population. With the weaker DSCP core promoter, K persisted for longer allowing the frequency of individuals with at least one copy of R to increase to over 98%. This simple gene drive system could be readily adapted to other species such as mosquito disease vectors for driving anti-viral or anti-parasite genes.\n\nSignificanceHere we report the development and testing of a novel self-limiting gene drive system, Killer-Rescue, in Drosophila melanogaster. This system is composed of an auto-regulated Gal4 Killer (K) and a Gal4-activated Gal80 Rescue (R). Overexpression of Gal4 is lethal but in the presence of R, activation of Gal80 leads to much lower levels of Gal4 and rescue of lethality. We demonstrate that with a single 2:1 engineered to wildtype release, more than 98% of the population carry R after eight generations. We discuss how this Killer-Rescue system may be used for population replacement in a human health pest, Aedes aegypti, or for population suppression in an agricultural pest, Drosophila suzukii.