Interaction of combined stressors and genetic background on recombination rate plasticity in Drosophila melanogaster

Abstract

Recombination is an important source of genetic variation and plays a central role in adaptation and genome stability. Although environmental conditions such as temperature can alter recombination rates, much less is known about how multiple environmental stressors act together. Here, we tested the effects of low temperature and hypoxia, both independently and in combination, on recombination in Drosophila melanogaster across five genetic backgrounds. Using a quadruple X-linked marker stock, we measured recombination in 50,209 male backcross progeny from 194 backcrosses exposed to four conditions: control, hypoxia, low temperature, and combined hypoxia and low temperature. Low temperature significantly altered recombination across all three chromosome intervals examined and affected total map length with an average increase of 5 cM. Genetic background strongly influenced the magnitude of altered recombination rate. Hypoxia alone did not significantly change total map length, but its effects differed among genetic backgrounds with significant variation in both the magnitude and direction with an average decrease of 0.96 cM. The response to combined hypoxia and low temperature was not simply the sum of the responses to each stressor alone, with an average increase of 6.78 cM, that also varied across genetic backgrounds in magnitude and direction as well as over time. DGRP_57 and DGRP_508 showed some of the largest increases in recombination under combined stress, whereas DGRP_491 showed a decrease. DGRP_391 was robust across all treatments. Despite these changes in crossover frequency, crossover interference remained largely stable across treatments, with only the y-cv-v interval pair showing a significant treatment-by-genotype interaction. Together, these results show that recombination responses to environmental stress depend strongly on genetic background and on the combination of stressors experienced. Our findings highlight the importance of considering both genetic variation and interacting environmental conditions when predicting how populations may respond to increasingly complex environmental change.