Biology subjects

Suzanne Eaton

Publications and source records attributed to Suzanne Eaton.

3 recordsLinked to original sources

bioRxiv2016

A temperature-dependent shift in dietary preference alters the viable temperature range of Drosophila

How cold-blooded animals adapt their behaviour and physiology to survive seasonal changes in temperature is not completely understood - even for well-studied model organisms like Drosophila melanogaster. Here, we show that Drosophila can extend their viable temperature range through temperature-dependent changes in feeding behaviour. Above 15{degrees}C, Drosophila feed and lay eggs on yeast. In contrast, below 15{degrees}C, Drosophila prefer to feed and lay eggs on plant material. The different lipids present in yeast and plants improve survival at high and low temperatures, respectively. Yeast lipids promote high tempera-ture survival by increasing systemic insulin signalling. This expands the range over which developmental rate increases with temperature, suggesting that faster nutrient utilization is required to fuel biochemical reactions driven faster by ki-netic energy. In addition to speeding development, yeast lipids increase fertility. Thus, yeast provide cues that could help Drosophila to exploit a transient summer food resource. Plant lipids, on the other hand, are required to maintain mem-brane lipid fluidity at low temperature, and increase cold-resistance of larvae and adults. The cold-resistance and lowered insulin signalling conferred by feeding on plants allows adults to survive for many months at temperatures consistent with overwintering in temperate climates. Thus, temperature-dependent changes in feeding behaviour produce physiological changes that could promote seasonal adaption.

Ecology↗

bioRxiv2014

Production of systemically circulating Hedgehog by the intestine couples nutrition to growth and development

In Drosophila larvae, growth and developmental timing are regulated by nutrition in a tightly coordinated fashion. The networks that couple these processes are far from understood. Here, we show that the intestine responds to nutrient availability by regulating production of a circulating lipoprotein associated form of the signaling protein Hedgehog (Hh). Levels of circulating Hh tune the rates of growth and developmental timing in a coordinated fashion. Circulating Hh signals to the fat body to control larval growth. It regulates developmental timing by controlling ecdysteroid production in the prothoracic gland. Circulating Hh is especially important during starvation, when it is also required for mobilization of fat body triacylglycerol (TAG) stores. Thus, we demonstrate that Hh, previously known only for its local morphogenetic functions, also acts as a lipoprotein-associated endocrine hormone, coordinating the response of multiple tissues to nutrient availability.

Developmental Biology↗

bioRxiv2013

Lipoproteins carry endocannabinoids that inhibit the Hedgehog pathway

Hedgehog proteins are lipid-modified secreted signaling molecules that regulate tissue development and homeostasis. Lipids contained in circulating lipoproteins repress the Hedgehog signaling pathway in the absence of Hedgehog ligand, but the identity of these lipids is unknown. Here, using biochemical fractionation and lipid mass spectrometry, we identify these inhibitory lipids as endocannabinoids. Endocannabinoids are present in lipoproteins of both flies and humans, and repress the pathway in both mammalian signaling assays and Drosophila wing imaginal discs. In Drosophila, endocannabinoids are required in vivo to keep the levels of Smoothened and full-length Cubitus interruptus (Ci155) low in the absence of Hedgehog. Furthermore, elevating their endogenous levels inhibits Hedgehog-dependent accumulation of Smoothened and Ci155. Interestingly, cannabis-derived phytocannabinoids are also potent pathway inhibitors in flies and mammals. These findings constitute a novel link between organismal metabolism and local Hedgehog signaling, and suggest previously unsuspected mechanisms for the broad physiological activities of cannabinoids.

Developmental Biology↗