The discordance between genome size and the complexity of eukaryotes can partly be attributed to differences in repeat density. The Muller F element (∼5.2 Mb) is the smallest chromosome in Drosophila melanogaster, but it is substantially larger (>18.7 Mb) in D. ananassae. To identify the major contributors to the expansion of the F element and to assess their impact, we improved the genome sequence and annotated the genes in a 1.4-Mb region of the D. ananassae F element, and a 1.7-Mb region from the D element for comparison. We find that transposons (particularly LTR and LINE retrotransposons) are major contributors to this expansion (78.6%), while Wolbachia sequences integrated into the D. ananassae genome are minor contributors (0.02%). Both D. melanogaster and D. ananassae F-element genes exhibit distinct characteristics compared to D-element genes (e.g., larger coding spans, larger introns, more coding exons, and lower codon bias), but these differences are exaggerated in D. ananassae. Compared to D. melanogaster, the codon bias observed in D. ananassae F-element genes can primarily be attributed to mutational biases instead of selection. The 5′ ends of F-element genes in both species are enriched in dimethylation of lysine 4 on histone 3 (H3K4me2), while the coding spans are enriched in H3K9me2. Despite differences in repeat density and gene characteristics, D. ananassae F-element genes show a similar range of expression levels compared to genes in euchromatic domains. This study improves our understanding of how transposons can affect genome size and how genes can function within highly repetitive domains.

Animals recognize the availability of nutrients and regulate the intake and storage of these nutrients accordingly. However, the molecular mechanisms underlying nutrient sensing and subsequent changes in behavior and metabolism are not fully understood. Mlx interactor (Mio), the Drosophila homolog of carbohydrate response element binding protein (ChREBP), functions as a transcription factor in the fat body of the fly to control triglyceride storage as well as feeding, suggesting that Mio may act in a nutrient-sensing pathway to coordinate food consumption and metabolism. Here, we show that Mio functions in neurons in Drosophila to regulate feeding and nutrient storage. Pan-neuronal disruption of Mio function leads to increased triglyceride and glycogen storage, and this phenotype is not due to increased food consumption. Interestingly, targeted disruption of Mio specifically in the insulin-producing cells (IPCs) has little effect on nutrient storage, but increases food consumption suggesting that Mio acts in these neurons to control feeding behavior. Since Mio is a transcription factor, one possible way Mio may act in the IPCs to control feeding is through regulating the expression of Drosophila insulin-like peptides (dilps) or drosulfakinin (dsk), neuropeptides produced in the IPCs. Consistent with this hypothesis, IPC-specific knockdown of Mio leads to an increase in dilp3 expression, while not affecting dilp2, 5 or dsk levels. Together, this study indicates a new function for Mio in the Drosophila brain and specifically in the IPCs, controlling neuropeptide gene expression, feeding and metabolism in accordance with nutrient availability.

All cells require energy to perform their specialized functions. Muscle is particularly sensitive to the availability of nutrients due to the high-energy requirement for muscle contraction. Therefore the ability of muscle cells to obtain, store and utilize energy is essential for the function of these cells. Mio, the Drosophila homolog of carbohydrate response element binding protein (ChREBP), has recently been identified as a nutrient responsive transcription factor important for triglyceride storage in the fly fat body. However, the function of Mio in muscle is unknown. In this study, we characterized the role of Mio in controlling muscle function and metabolism. Decreasing Mio levels using RNAi specifically in muscle results in increased thorax glycogen storage. Adult Mio-RNAi flies also have a flight defect due to altered myofibril shape and size in the indirect flight muscles as shown by electron microscopy. Myofibril size is also decreased in flies just before emerging from their pupal cases, suggesting a role for Mio in myofibril development. Together, these data indicate a novel role for Mio in controlling muscle structure and metabolism and may provide a molecular link between nutrient availability and muscle function.

Context Muscle damage and delayed onset muscle soreness (DOMS) can occur following intense exercise. Various modalities have been studied to improve blood lactate accumulation, which is a primary reason for DOMS. It has been well established that active recovery facilitates blood lactate removal more rapidly that passive recovery due to the pumping action of the muscle. The pedal pump is a manual lymphatic technique used in osteopathic manipulative medicine to increase lymphatic drainage throughout the body. Pedal pump has been shown to increase lymphatic flow and improve immunity. This may improve circulation and improve clearance of metabolites post-exercise. Objective This study compared the use of pedal pump lymphatic technique to passive supine recovery following maximal exercise. Methods 17 subjects (male n = 10, age 23 ± 3.01; female n = 7, age 24 ± 1.8), performed a maximal volume O2 test (VO2 max) using a Bruce protocol, followed by a recovery protocol using either pedal pump technique or supine passive rest for 10 min, followed by sitting for 10 min. Outcome measures included blood lactate concentration (BL), heart rate (HR), systolic blood pressure (SBP) and VO2. Subjects returned on another day to repeat the VO2 max test to perform the other recovery protocol. All outcomes were measured at rest, within 1- minute post-peak exercise, and at minutes 4, 7, 10 and 20 of the recovery protocols. A 2 × 6 repeated measures ANOVA was used to compare outcome measures (p ≤ 0.05). Results No significant differences were found in VO2, HR, or SBP between any of the recovery protocols. There was no significant difference in BL concentrations for recovery at minutes 4, 7, or 10 (p > 0.05). However, the pedal pump recovery displayed significantly lower BL concentrations at minute 20 of recovery (p = 0.04). Conclusion The pedal pump significantly decreased blood lactate concentrations following intense exercise at recovery minute 20. The use of manual lymphatic techniques in exercise recovery should be investigated further.