Trans-interactions at Men in Drosophila melanogaster demonstrate environmental plasticity. Xinyang Bing¹, Teresa Rzezniczak², Thomas Merritt¹. 1) Chemistry and Biochemistry, Laurentian University, Sudbury, Ontario, Canada; 2) Institute of Biochemistry, Carleton University, Ottawa, ON, K1S 5B6, Canada.

   We found that trans-regulation, a little understood but potentially wide-spread form of transcriptional regulation, is sensitive to changes in both large-scale genetic background and environmental conditions. Interestingly, these trans-interactions may be sensitive to background and environment even when the better understood cis-interactions are not. Further, these trans-interactions appear to be mediated through changes in binding transcription factors, possibly in a tissue specific manner. Together, our results support a dynamic view of the Drosophila genome, including complex chromosomal interactions on a genome-wide basis, in response to changes in the environment. Specifically, we changed the post-eclosion environment of a series of adult flies that exhibit varying levels of trans-interactions at Malic enzyme (Men) in different genetic backgrounds, and assayed MEN activity. We found that shifting the post-eclosion environment to higher or lower temperatures significantly reduced MEN activity overall. Post-eclosion temperature also significantly reduced the amount of trans-interactions observed, and the amount of interaction between each knockout allele and genetic background. However, cis-interactions were not significantly affected by post-eclosion temperature. Next, using qPCR, we found significant differences in Men expression across post-eclosion temperature, and significant correlations between Men expression and MEN activity with the expression of Abd-B and mirr. Lastly, we demonstrate that knockdown of Abd-B and mirr significantly affected both Men expression and MEN activity.