Transvection-based gene regulation in Drosophila is a complex and plastic trait.
Bottom Line: We further show that the magnitude of transvection at the Men locus is modified by both genetic background and environment (temperature), demonstrating that transvection is a plastic phenotype.Our results suggest that transvection effects in D. melanogaster are shaped by a dynamic interplay between environment and genetic background.Interestingly, we find that cis-based regulation of the Men gene is more robust to genetic background and environment than trans-based.
Affiliation: Department of Chemistry and Biochemistry, Laurentian University, Sudbury, ON, P3E 2C6, Canada.Show MeSH
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Mentions: The predicted TFBSs described previously are present in multiple copies within highly conserved regions across the Men locus (Figure 5A; Lum and Merritt 2011) and we suspected that TFs bound to these sites could regulate Men expression in cis, in addition to any role in trans-regulation. Using RNAi, we reduced the expression of three TF genes with binding sites in this region, Abd-B, mirr, and slbo, and assayed for differences in Men expression and MEN activity (Figure 8A). Abd-B was selected because of its correlation with transvection at Men described previously, whereas mirr and slbo were selected as a contrast because no consistent correlations were found with these genes in trans. Following reports of larger RNAi effects with multiple heat shocks (Kristensen et al. 2003), vials were heat shocked five times to induce expression of hairpins: 1, 2, 4, 8, and 12 days after egg laying, resulting in reproducible reduction in TF expression (Figure 8). Note that all heat shock treatments were administered postembryogenesis to avoid the primary period during which Abd-B functions in embryonic patterning (Graveley et al. 2011, Akam 1987), and that no gross morphological changes were observed in any knockdown flies. Notably, Men expression and MEN activity were both significantly reduced only in flies that had Abd-B expression knocked down (Figure 8, B and C and Table S3). The reduction in malic enzyme with only a 50% reduction in Abd-B may be surprising at first, but previous studies have found malic enzyme to be sensitive to small differences in activity of other genes or the environment (e.g., Merritt et al. 2005; Geer et al. 1976). These results, and the correlation of Abd-B and Men expression seen in the previous experiment, support a model in which Abd-B plays a role in the regulation of Men expression both in cis and in trans.
Affiliation: Department of Chemistry and Biochemistry, Laurentian University, Sudbury, ON, P3E 2C6, Canada.