Abiotic environments can modify the penetrance of a transgene-based lethality system for genetic biocontrol of insect populations

Genetic biocontrol approaches to insect pest management offer high species specificity and reduce insecticidal chemical pollution, but these approaches require the release of genetically modified organisms that must perform across a variety of environmental conditions. Because organisms often display phenotypic and gene expression variability when exposed to different environments, it is reasonable to expect that transgenic systems may be prone to environmentally mediated variation in expression and function. In this study, we examined the influence of two abiotic variables, temperature and nutrition, on the penetrance of an early embryonic Tet-off conditional lethality system in the vinegar fly, Drosophila melanogaster . We manipulated parental and offspring environments independently to determine the impact of life stage of exposure on transgene performance by estimating the probability of larval hatching and measuring transcript abundance of the transgenic system components. Our findings revealed that: 1) transgene performance has distinct norms of reaction to temperature and nutrition, 2) the effects of abiotic challenge are greatest when exposure occurs in the embryos expressing the transgene compared to parental exposure, and 3) stress exposures at the extreme limits of permissible conditions can dramatically decrease the penetrance of transgenic lethality. While variation in transcript abundance of the transgenic system was observed in some environments, these changes were not fully congruent with patterns of phenotypic penetrance, suggesting that the observed variation in lethality is likely driven by processes downstream of transcription.