Mitonuclear incompatibilities may manifest as differences in energetic output and ability to recover from exposure to stressful conditions. The strength of a mitonuclear incompatibility is influenced by exposure to physiological stress and may vary along environmental gradients. Our understanding of mechanisms underlying mitonuclear incompatibilities may be improved by examining transcriptional responses to interacting stress factors. We examined effects of reduced oxygen supply and heat stress exposure on gene expression for the montane leaf beetle Chrysomela aeneicollis. Beetle larvae were reared at 1500 m (low elevation) or 3090 m (natural elevation) above sea level. When they reached the third instar, we measured their performance, exposed them to a control (20C) or thermally stressful temperature (36C), and measured performance after stress. Results revealed that beetles reared at natural elevation recovered better than beetles reared at low elevation, and mitochondrial and nuclear genotypes related to stress recovery. We quantified gene expression in 96 individuals and found that both genotype and stress exposure have an effect on the relative expression levels of genes. Results will be further described in this talk.