Carvalho, Maria João A.; Mirth, Christen K.
Animals in the wild live in highly variable and unpredictable environments. This variation in their habitat induces animals, at all stages of their development, to make decisions about what to eat, where to live, and with whom to associate. Additionally, animals like insects show dramatic restructuring of their morphology across life stages, which is accompanied by alterations in their behavior to match stage-specific functions. Finally, in a process called developmental plasticity, environmental conditions feed back onto developmental mechanisms producing animals with stage-specific variation in both morphological and behavioral traits. In this review, we use examples from insects to explore the...
Mendes, C. C.; Mirth, C. K.
Animals from flies to humans adjust their development in response to environmental conditions through a series of developmental checkpoints, which alter the sensitivity of organs to environmental perturbation. Despite their importance, we know little about the molecular mechanisms through which this change in sensitivity occurs. Here we identify two phases of sensitivity to larval nutrition that contribute to plasticity in ovariole number, an important determinant of fecundity, in Drosophila melanogaster. These two phases of sensitivity are separated by the developmental checkpoint called "critical weight"; poor nutrition has greater effects on ovariole number in larvae before critical weight than after. We...
Rodrigues, Marisa A.; Martins, Nelson E.; Balancé, Lara F.; Broom, Lara N.; Dias, António J.S.; Fernandes, Ana Sofia D.; Rodrigues, Fábio; Sucena, Élio; Mirth, Christen K.
Organisms from slime moulds to humans carefully regulate their macronutrient intake to optimize a wide range of life history characters including survival, stress resistance, and reproductive success. However, life history characters often differ in their response to nutrition, forcing organisms to make foraging decisions while balancing the trade-offs between these effects. To date, we have a limited understanding of how the nutritional environment shapes the relationship between life history characters and foraging decisions. To gain insight into the problem, we used a geometric framework for nutrition to assess how the protein and carbohydrate content of the larval diet affected key...
Matavelli, Cristiane; Carvalho, Maria João A.; Martins, Nelson E.; Mirth, Christen K.
Species coexist using the same nutritional resource by partitioning it either in space or time, but few studies explore how species-specific nutritional requirements allow partitioning. Zaprionus indianus and Drosophila simulans co-exist in figs by invading the fruit at different stages; Z. indianus colonizes ripe figs, whereas D. simulans oviposits in decaying fruit. Larvae feed on yeast growing on the fruit, which serves as their primary protein source. Because yeast populations increase as fruit decays, we find that ripe fruit has lower protein content than rotting fruit. Therefore, we hypothesized that Z. indianus and D. simulans larvae differ in their dietary...
Nijhout, H. Frederik; Riddiford, Lynn M.; Mirth, Christen; Shingleton, Alexander W.; Suzuki, Yuichiro; Callier, Viviane
The mechanisms that control the sizes of a body and its many parts remain among the great puzzles in developmental biology. Why do animals grow to a species-specific body size, and how is the relative growth of their body parts controlled to so they grow to the right size, and in the correct proportion with body size, giving an animal its species-characteristic shape? Control of size must involve mechanisms that somehow assess some aspect of size and are upstream of mechanisms that regulate growth. These mechanisms are now beginning to be understood in the insects, in particular in Manduca sexta...
Kabra, Mayank; Robie, Alice A; Rivera-Alba, Marta; Branson, Steven; Branson, Kristin
We present a machine learning-based system for automatically computing interpretable, quantitative measures of animal behavior. Through our interactive system, users encode their intuition about behavior by annotating a small set of video frames. These manual labels are converted into classifiers that can automatically annotate behaviors in screen-scale data sets. Our general-purpose system can create a variety of accurate individual and social behavior classifiers for different organisms, including mice and adult and larval Drosophila.
Mirth, Christen Kerry; Shingleton, Alexander W.
OVER THE PAST TWO DECADES, FUNDAMENTAL STRIDES IN PHYSIOLOGY AND GENETICS HAVE ALLOWED US TO FINALLY GRASP THE DEVELOPMENTAL MECHANISMS REGULATING BODY SIZE, PRIMARILY IN ONE MODEL ORGANISM: the fruit fly Drosophila melanogaster. In Drosophila, as in all animals, final body size is regulated by the rate and duration of growth. These studies have identified important roles for the insulin and the target of rapamycin (TOR) signaling pathways in regulating the growth rate of the larva, the stage most important in determining final adult size. Furthermore, they have shown that the insulin/TOR pathway interacts with hormonal systems, like ecdysone and...
Koyama, Takashi; Rodrigues, Marisa A; Athanasiadis, Alekos; Shingleton, Alexander W; Mirth, Christen K
Despite their fundamental importance for body size regulation, the mechanisms that stop growth are poorly understood. In Drosophila melanogaster, growth ceases in response to a peak of the molting hormone ecdysone that coincides with a nutrition-dependent checkpoint, critical weight. Previous studies indicate that insulin/insulin-like growth factor signaling (IIS)/Target of Rapamycin (TOR) signaling in the prothoracic glands (PGs) regulates ecdysone biosynthesis and critical weight. Here we elucidate a mechanism through which this occurs. We show that Forkhead Box class O (FoxO), a negative regulator of IIS/TOR, directly interacts with Ultraspiracle (Usp), part of the ecdysone receptor. While overexpressing FoxO in the...
Herboso, Leire; Oliveira, Marisa M.; Talamillo, Ana; Pérez, Coralia; González, Monika; Martín, David; Sutherland, James D.; Shingleton, Alexander W.; Mirth, Christen K.; Barrio, Rosa
Animals have a determined species-specific body size that results from the combined action of hormones and signaling pathways regulating growth rate and duration. In Drosophila, the steroid hormone ecdysone controls developmental transitions, thereby regulating the duration of the growth period. Here we show that ecdysone promotes the growth of imaginal discs in mid-third instar larvae, since imaginal discs from larvae with reduced or no ecdysone synthesis are smaller than wild type due to smaller and fewer cells. We show that insulin-like peptides are produced and secreted normally in larvae with reduced ecdysone synthesis, and upstream components of insulin/insulin-like signaling are...
Koyama, Takashi; Mirth, Christen K.
In Drosophila, the fat body, functionally equivalent to the mammalian liver and adipocytes, plays a central role in regulating systemic growth in response to nutrition. The fat body senses intracellular amino acids through Target of Rapamycin (TOR) signaling, and produces an unidentified humoral factor(s) to regulate insulin-like peptide (ILP) synthesis and/or secretion in the insulin-producing cells. Here, we find that two peptides, Growth-Blocking Peptide (GBP1) and CG11395 (GBP2), are produced in the fat body in response to amino acids and TOR signaling. Reducing the expression of GBP1 and GBP2 (GBPs) specifically in the fat body results in smaller body size...