AGES for Ageing: Evaluating the auxin-inducible gene expression system for use in Drosophila ageing studies

Our research is only as good as our tools allow it to be. The fruit fly Drosophila has been a fundamental discovery platform in uncovering evolutionarily conserved biological underpinnings of ageing, due in large part to an ever-expanding functional genetic toolbox which permits fine-tuneable and cell-type-specific modulation of gene expression with relative ease. However, many existing gene expression systems present limitations for studying fly ageing, including off-target effects for inducing agents that allow temporal control. More recently-generated tools such as the auxin-based gene expression system (AGES) therefore present opportunities as potential alternatives in our methodological repertoire for ageing research. Here we have evaluated the AGES system in a variety of contexts in Drosophila ageing. We find that AGES can effectively induce transgene expression across a range of ages, albeit with tissue-specific efficiency. However, we also observe several phenotypes from auxin feeding, even in non-AGES genotypes, that may confound studies focused on ageing research, including reduced body mass and reduced survival under starvation and oxidative stress conditions. We also observe phenotypes from activating the AGES machinery, including shortened lifespan, that could present challenges for using AGES in longevity-based studies. Nevertheless, we find that AGES can be used to recapitulate at least some effects of well-established pro-longevity interventions - for instance reduced fecundity from expression of a dominant-negative form of the insulin receptor - reinforcing the value of AGES in certain domains. Taken together, our results underscore the need for caution and comprehensive controls in ageing studies that rely on functional genetics, regardless of the chosen genetic toolset.