FGF signaling promotes spreading of fat body precursors necessary for adult adipogenesis in Drosophila

Cell deformations generated by stochastic actomyosin waves drive in vivo random-walk swimming migration

Amoeboid cell migration drives many developmental and disease-related processes, including immune responses and cancer metastasis. Swimming migration is a subtype of amoeboid migration that is observed in cells in suspension ex vivo. However, the mechanism underlying swimming migration in vivo is unknown. Using Drosophila fat body cells (FBCs) as a model, we show that FBCs actively swim to patrol the pupa by random walk. Their migration is powered through actomyosin waves that exert compressive forces as they travel to the cell rear, causing cell deformations. Unlike in other types of amoeboid migration, Rho1 (the Drosophila orthologue of RhoA), Cdc42 and Rac1 are all required for regulation of formin-driven actin polymerization during FBC migration. We find that Rho1 at the cell rear induces actomyosin contractions via Rho kinase and myosin II. We show that contractile actin waves display a stochastic behaviour, inducing either cell elongation or rounding, suggesting that non-reciprocal cell deformations drive locomotion. Importantly, our work in a physiological system reveals that stochastic actomyosin waves promote random-walk swimming migration to enable fast, long-range cell dispersal. We propose that this individualist migration behaviour collectively allows patrolling of the pupal body.

Neuroecology of alcohol risk and reward: Methanol boosts pheromones and courtship success in Drosophila melanogaster

Attraction of Drosophila melanogaster toward by-products of alcoholic fermentation, especially ethanol, has been extensively studied. Previous research has provided several interpretations of this attraction, including potential drug abuse, or a self-medicating coping strategy after mate rejection. We posit that the ecologically adaptive value of alcohol attraction has not been fully explored. Here, we assert a simple yet vital biological rationale for this alcohol preference. Flies display attraction to fruits rich in alcohol, specifically ethanol and methanol, where contact results in a rapid amplification of fatty acid-derived pheromones that enhance courtship success. We also identify olfactory sensory neurons that detect these alcohols, where we reveal roles in both attraction and aversion, and show that valence is balanced around alcohol concentration. Moreover, we demonstrate that methanol can be deadly, and adult flies must therefore accurately weigh the trade-off between benefits and costs for exposure within their naturally fermented and alcohol-rich environments.

Developmental mitochondrial complex I activity determines lifespan

Aberrant mitochondrial function has been associated with an increasingly large number of human disease states. Observations from in vivo models where mitochondrial function is altered suggest that maladaptations to mitochondrial dysfunction may underpin disease pathology. We hypothesized that the severity of this maladaptation could be shaped by the plasticity of the system when mitochondrial dysfunction manifests. To investigate this, we have used inducible fly models of mitochondrial complex I (CI) dysfunction to reduce mitochondrial function at two stages of the fly lifecycle, from early development and adult eclosion. Here, we show that in early life (developmental) mitochondrial dysfunction results in severe reductions in survival and stress resistance in adulthood, while flies where mitochondrial function is perturbed from adulthood, are long-lived and stress resistant despite having up to a 75% reduction in CI activity. After excluding developmental defects as a cause, we went on to molecularly characterize these two populations of mitochondrially compromised flies, short- and long-lived. We find that our short-lived flies have unique transcriptomic, proteomic and metabolomic responses, which overlap significantly in discrete models of CI dysfunction. Our data demonstrate that early mitochondrial dysfunction via CI depletion elicits a maladaptive response, which severely reduces survival, while CI depletion from adulthood is insufficient to reduce survival and stress resistance.

Temperature-dependent dynamics of energy stores in Drosophila

BACKGROUND

Understanding how ectotherms manage energy in response to temperature is crucial for predicting their responses to climate change. However, the complex interplay between developmental and adult thermal conditions on total energy stores remains poorly understood. Here, we present the first comprehensive quantification of this relationship in Drosophila melanogaster, a model ectotherm, across its entire thermal tolerance range. To account for potential intraspecific variation, we used flies from two distinct populations originating from different climate zones. Utilizing a full factorial design, we assessed the effects of both developmental and adult temperatures on the amount of key energy macromolecules (fat, glycogen, trehalose, and glucose). Importantly, by quantifying these macromolecules, we were able to calculate the total available energy.

RESULTS

Our findings reveal that the dynamic interplay between developmental and adult temperatures profoundly influences the energy balance in Drosophila. The total energy reserves exhibited a quadratic response to adult temperature, with an optimal range of 18-21 °C for maximizing energy levels. Additionally, the temperature during development considerably affected maximum energy stores, with the highest reserves observed at a developmental temperature of approximately 20-21 °C. Deviations from this relatively narrow optimal thermal range markedly reduced energy stores, with each 1 °C increase above 25 °C diminishing energy reserves by approximately 15%.

CONCLUSIONS

This study highlights the critical and interacting roles of both developmental and adult thermal conditions in shaping Drosophila energy reserves, with potentially profound implications for fitness, survival, and ecological interactions under future climate scenarios.

Improved whole-mount immunofluorescence protocol for consistent and robust labeling of adult Drosophila melanogaster adipose tissue

Energy storage and endocrine functions of the Drosophila fat body make it an excellent model for elucidating mechanisms that underlie physiological and pathophysiological organismal metabolism. Combined with Drosophila's robust genetic and immunofluorescence microscopy toolkits, studies of Drosophila fat body function are ripe for cell biological analysis. Unlike the larval fat body, which is easily removed as a single, cohesive sheet of tissue, isolating intact adult fat body proves to be more challenging, thus hindering consistent immunofluorescence labeling even within a single piece of adipose tissue. Here, we describe an improved approach to handling Drosophila abdomens that ensures full access of the adult fat body to solutions generally used in immunofluorescence labeling protocols. In addition, we assess the quality of fluorescence reporter expression and antibody immunoreactivity in response to variations in fixative type, fixation incubation time, and detergent used for cellular permeabilization. Overall, we provide several recommendations for steps in a whole-mount staining protocol that results in consistent and robust immunofluorescence labeling of the adult Drosophila fat body.

Macrophages play a nutritive role in post-metamorphic maturation in Drosophila

In the body of multicellular organisms, macrophages play an indispensable role in maintaining tissue homeostasis by removing old, apoptotic and damaged cells. In addition, macrophages allow significant remodeling of body plans during embryonic morphogenesis, regeneration and metamorphosis. Although the huge amount of organic matter that must be removed during these processes represents a potential source of nutrients, their further use by the organism has not yet been addressed. Here, we document that, during metamorphosis, Drosophila larval adipose tissue is infiltrated by macrophages, which remove dying adipocytes by efferocytosis and engulf leaking RNA-protein granules and lipids. Consequently, the infiltrating macrophages transiently adopt the adipocyte-like metabolic profile to convert remnants of dying adipocytes to lipoproteins and storage peptides that nutritionally support post-metamorphic development. This process is fundamental for the full maturation of ovaries and the achievement of early fecundity of individuals. Whether macrophages play an analogous role in other situations of apoptotic cell removal remains to be elucidated.