@article {6883, title = {The developmental control of size in insects.}, journal = {Wiley Interdisciplinary Reviews: Developmental Biology}, volume = {3}, year = {2014}, month = {2014 Jan/Feb}, pages = {113-34}, abstract = {

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 and Drosophila melanogaster. The control of size requires control of the rate of growth and control of the cessation of growth. Growth is controlled by genetic and environmental factors. Insulin and ecdysone, their receptors, and intracellular signaling pathways are the principal genetic regulators of growth. The secretion of these growth hormones, in turn, is controlled by complex interactions of other endocrine and molecular mechanisms, by environmental factors such as nutrition, and by the physiological mechanisms that sense body size. Although the general mechanisms of growth regulation appear to be widely shared, the mechanisms that regulate final size can be quite diverse. WIREs Dev Biol 2014, 3:113{\textendash}134. doi: 10.1002/wdev.124

}, issn = {1759-7684}, doi = {10.1002/wdev.124}, author = {Nijhout, H. Frederik and Riddiford, Lynn M and Mirth, Christen and Shingleton, Alexander W and Suzuki, Yuichiro and Callier, Viviane} } @article {6525, title = {Developmental model of static allometry in holometabolous insects.}, journal = {Proceedings of the Royal Society B: Biological Sciences}, volume = {275}, year = {2008}, month = {2008 Aug 22}, pages = {1875-85}, abstract = {

The regulation of static allometry is a fundamental developmental process, yet little is understood of the mechanisms that ensure organs scale correctly across a range of body sizes. Recent studies have revealed the physiological and genetic mechanisms that control nutritional variation in the final body and organ size in holometabolous insects. The implications these mechanisms have for the regulation of static allometry is, however, unknown. Here, we formulate a mathematical description of the nutritional control of body and organ size in Drosophila melanogaster and use it to explore how the developmental regulators of size influence static allometry. The model suggests that the slope of nutritional static allometries, the {\textquoteright}allometric coefficient{\textquoteright}, is controlled by the relative sensitivity of an organ{\textquoteright}s growth rate to changes in nutrition, and the relative duration of development when nutrition affects an organ{\textquoteright}s final size. The model also predicts that, in order to maintain correct scaling, sensitivity to changes in nutrition varies among organs, and within organs through time. We present experimental data that support these predictions. By revealing how specific physiological and genetic regulators of size influence allometry, the model serves to identify developmental processes upon which evolution may act to alter scaling relationships.

}, keywords = {Animal Nutritional Physiological Phenomena, Animals, Biological, Biometry, Body Size, Drosophila, Metamorphosis, Models, Organ Size}, issn = {0962-8452}, doi = {10.1098/rspb.2008.0227}, author = {Shingleton, Alexander W and Mirth, Christen K and Bates, Peter W} } @article {45755, title = {The origin of a mutualism: a morphological trait promoting the evolution of ant-aphid mutualisms.}, journal = {Evolution}, volume = {59}, year = {2005}, month = {2005 Apr}, pages = {921-6}, abstract = {

Mutualisms are mutually beneficial interactions between species and are fundamentally important at all levels of biological organization. It is not clear, however, why one species participates in a particular mutualism whereas another does not. Here we show that pre-existing traits can dispose particular species to evolve a mutualistic interaction. Combining morphological, ecological, and behavioral data in a comparative analysis, we show that resource use in Chaitophorus aphids (Hemiptera: Aphididae) modulates the origin of their mutualism with ants. We demonstrate that aphid species that feed on deeper phloem elements have longer mouthparts, that this inhibits their ability to withdraw their mouthparts and escape predators and that, consequently, this increases their need for protection by mutualist ants.

}, keywords = {Animals, Ants, Aphids, Biological Evolution, Body Weights and Measures, Feeding Behavior, Great Britain, Mouth, Symbiosis}, issn = {0014-3820}, author = {Shingleton, Alexander W and Stern, David L and Foster, William A} } @article {45754, title = {The temporal requirements for insulin signaling during development in Drosophila.}, journal = {PLoS Biol}, volume = {3}, year = {2005}, month = {2005 Sep}, pages = {e289}, abstract = {

Recent studies have indicated that the insulin-signaling pathway controls body and organ size in Drosophila, and most metazoans, by signaling nutritional conditions to the growing organs. The temporal requirements for insulin signaling during development are, however, unknown. Using a temperature-sensitive insulin receptor (Inr) mutation in Drosophila, we show that the developmental requirements for Inr activity are organ specific and vary in time. Early in development, before larvae reach the "critical size" (the size at which they commit to metamorphosis and can complete development without further feeding), Inr activity influences total development time but not final body and organ size. After critical size, Inr activity no longer affects total development time but does influence final body and organ size. Final body size is affected by Inr activity from critical size until pupariation, whereas final organ size is sensitive to Inr activity from critical size until early pupal development. In addition, different organs show different sensitivities to changes in Inr activity for different periods of development, implicating the insulin pathway in the control of organ allometry. The reduction in Inr activity is accompanied by a two-fold increase in free-sugar levels, similar to the effect of reduced insulin signaling in mammals. Finally, we find that varying the magnitude of Inr activity has different effects on cell size and cell number in the fly wing, providing a potential linkage between the mode of action of insulin signaling and the distinct downstream controls of cell size and number. We present a model that incorporates the effects of the insulin-signaling pathway into the Drosophila life cycle. We hypothesize that the insulin-signaling pathway controls such diverse effects as total developmental time, total body size and organ size through its effects on the rate of cell growth, and proliferation in different organs.

}, keywords = {Animals, Drosophila, Drosophila Proteins, Insect Hormones, Insulin, Insulin Receptor Substrate Proteins, Intracellular Signaling Peptides and Proteins, Larva, Mutation, Receptor Protein-Tyrosine Kinases, Signal Transduction, Time Factors}, issn = {1545-7885}, doi = {10.1371/journal.pbio.0030289}, author = {Shingleton, Alexander W and Das, Jayatri and Vinicius, Lucio and Stern, David L} } @article {45761, title = {Developmental origin and evolution of bacteriocytes in the aphid-Buchnera symbiosis.}, journal = {PLoS Biol}, volume = {1}, year = {2003}, month = {2003 Oct}, pages = {E21}, abstract = {

Symbiotic relationships between bacteria and insect hosts are common. Although the bacterial endosymbionts have been subjected to intense investigation, little is known of the host cells in which they reside, the bacteriocytes. We have studied the development and evolution of aphid bacteriocytes, the host cells that contain the endosymbiotic bacteria Buchnera aphidicola. We show that bacteriocytes of Acyrthosiphon pisum express several gene products (or their paralogues): Distal-less, Ultrabithorax/Abdominal-A, and Engrailed. Using these markers, we find that a subpopulation of the bacteriocytes is specified prior to the transmission of maternal bacteria to the embryo. In addition, we discovered that a second population of cells is recruited to the bacteriocyte fate later in development. We experimentally demonstrate that bacteriocyte induction and proliferation occur independently of B. aphidicola. Major features of bacteriocyte development, including the two-step recruitment of bacteriocytes, have been conserved in aphids for 80-150 million years. Furthermore, we have investigated two cases of evolutionary loss of bacterial symbionts: in one case, where novel extracellular, eukaryotic symbionts replaced the bacteria, the bacteriocyte is maintained; in another case, where symbionts are absent, the bacteriocytes are initiated but not maintained. The bacteriocyte represents an evolutionarily novel cell fate, which is developmentally determined independently of the bacteria. Three of five transcription factors we examined show novel expression patterns in bacteriocytes, suggesting that bacteriocytes may have evolved to express many additional transcription factors. The evolutionary transition to a symbiosis in which bacteria and an aphid cell form a functional unit, similar to the origin of plastids, has apparently involved extensive molecular adaptations on the part of the host cell.

}, keywords = {Animals, Aphids, Buchnera, Cell Lineage, Drosophila Proteins, Evolution, Molecular, Female, Gene Expression Regulation, Bacterial, Homeodomain Proteins, Male, Microscopy, Fluorescence, Models, Biological, Parthenogenesis, Species Specificity, Symbiosis, Time Factors, Transcription Factors}, issn = {1545-7885}, doi = {10.1371/journal.pbio.0000021}, author = {Braendle, Christian and Miura, Toru and Bickel, Ryan and Shingleton, Alexander W and Kambhampati, Srinivas and Stern, David L} } @article {45763, title = {Diapause in the pea aphid (Acyrthosiphon pisum) is a slowing but not a cessation of development.}, journal = {BMC Dev Biol}, volume = {3}, year = {2003}, month = {2003 Aug 8}, pages = {7}, abstract = {

BACKGROUND: Many insects undergo a period of arrested development, called diapause, to avoid seasonally recurring adverse conditions. Whilst the phenology and endocrinology of insect diapause have been well studied, there has been comparatively little research into the developmental details of diapause. We investigated developmental aspects of diapause in sexually-produced embryos of the pea aphid, Acyrthosiphon pisum.

RESULTS: We found that early stages of embryogenesis progressed at a temperature-independent rate, characteristic of diapause, whereas later stages of embryogenesis progressed at a temperature-dependent rate. However, embryos maintained at very high temperatures during the temperature-independent stage showed severe developmental abnormalities. Under no temperature regime did embryos display a distinct resting stage. Rather, morphological development progressed slowly but continuously throughout embryogenesis.

CONCLUSION: Diapause in the pea aphid, and perhaps in many other insects, is a temperature-independent slowing but not a cessation of morphological development. This suggests that the mechanisms limiting developmental rate during diapause may be the same as those controlling developmental rate at other stages of growth.

}, keywords = {Animals, Aphids, Female, Life Cycle Stages, Male, Peas, Temperature}, issn = {1471-213X}, doi = {10.1186/1471-213X-3-7}, author = {Shingleton, Alexander W and Sisk, Geoffroy C and Stern, David L} } @article {45767, title = {Molecular phylogenetic evidence for multiple gains or losses of ant mutualism within the aphid genus Chaitophorus.}, journal = {Mol Phylogenet Evol}, volume = {26}, year = {2003}, month = {2003 Jan}, pages = {26-35}, abstract = {

Mutualism with ants is suspected to be a highly labile trait within homopteran evolution. We used molecular phylogenetic evidence to test whether the mutualism has multiple origins within a single aphid genus. We constructed a molecular phylogeny of 15 Chaitophorus Koch (Hemiptera: Aphidoidea) species, using mitochondrial cytochrome oxidase I and II sequences. Ant tending evolved, or was lost, at least five times during Chaitophorus evolution. Parametric bootstrapping rejected the hypothesis of a single origin of ant tending in this genus. Further, the Chaitophorus made at least two host genus switches from poplars (Populus) to willow (Salix), and four switches in feeding position, from leaf feeding to stem feeding or vice versa. This is the first phylogenetic confirmation that ant tending is an evolutionarily labile trait in aphids.

}, keywords = {Animals, Ants, Aphids, Behavior, Animal, Evolution, Molecular, Phylogeny, Symbiosis}, issn = {1055-7903}, author = {Shingleton, Alexander W and Stern, David L} }