Body Size In Drosophila Research Articles

Life history changes associated with over 400 generations of artificial selection on body size in Drosophila.

Body size is a trait that shapes many aspects of a species' development and evolution. Larger body size is often beneficial in animals, but it can also be associated with life history costs in natural systems. Similarly, miniaturization, the evolution of extremely small adult body size, is found in every major animal group, yet carries its own life history trade-offs. Given that these effects can depend on an animal's environment and life stage and have mainly been studied in species that are already specialized for their size, the life history changes associated with evolutionary shifts in body size warrant additional investigation. Here, we used Drosophila melanogaster populations that had undergone over 400 generations of artificial selection on body size to investigate the changes in life history traits associated with the evolution of extremely large and extremely small body sizes. Populations selected for small body size experienced strong trade-offs in multiple life history traits, including reduced female fecundity and lower juvenile viability. Although we found positively correlated changes in egg size associated with selection for both large and small body size, after adjusting for female body size, females from populations selected for large size had the lowest relative investment per egg and females from populations selected for small size had the highest relative investment per egg. Taken together, our results suggest that egg size may be a key constraint on the evolution of body size in D. melanogaster, providing insight into the broader phenomenon of body size evolution in insects.

Generation of a Floxed Allele of the Mouse MicroRNA-200 Clusters

MicroRNA-8 and its target gene, u-shaped (ush), regulate body size in Drosophila. As the mouse homolog of the Drosophila miR-8, whether the miR-200 family has similar functions and how they perform their regulatory roles in body size control is unknown. In order to discover the biological function of the miR-200s in vivo, we generated mice lacking the miR-200b/200a/429 gene cluster using the Cre/loxp system. miR-200b/200a/429 null mutant mice were viable, fertile, and showed normal development.

Do Late‐Instar Drosophila Larvae Experience Functional Oxygen Limitations?

Arthropods gain considerable mass between molts, increasing oxygen demand while parts of the respiratory system are fixed in size. We hypothesized that internal hypoxia could be a cue triggering molting in arthropods and/or be a functional reason that the animal needs to molt. In support of this hypothesis, hypoxic rearing (10 kPa) triggered an ecdysone peak and molting to adulthood at a smaller body size in Drosophila, and hyperoxia induced earlier pupariation (JEB 216:4334). We tested for evidence that late‐third instar Drosophila larvae show signs of functional oxygen‐limitation. The dorsal longitudinal tracheae increased in diameter through the instar, scaling with mass0.38, approximately as predicted to conserve oxygen delivery. Respiratory exchange ratios declined through the instar, indicating that metabolism remains aerobic and shifts away from carbohydrate catabolism. Lactate levels did not increase later in the instar and were unaffected by rearing in hyperoxia. However, hyperoxia (30 kPa) increased late‐instar metabolic rates, suggesting functional oxygen limitation. Late‐instar larvae had greater capacities to generate lactate in response to anoxia, suggesting past selection for coping with late‐instar oxygen limitation. Most late‐ but not early‐stage larvae unregulated HIF signaling. Together these data support the conclusion that Drosophila, and likely other arthropods, experience some functional oxygen limitations later in the instar that trigger HIF signaling, potentially linked to the molting cascade. This research was supported by NSF IOS 1256745.

Temperature and developmental responses of body and cell size in Drosophila; effects of polyploidy and genome configuration

Increased adult body size in Drosophila raised at lower temperatures could be attributed both to an increase in the cell volume and cell number. It is not clear, however, whether increased cell size is related to (or even caused by) increased nuclear volume and genome size (or configuration). Experiments with Drosophila melanogaster stocks (Oregon-R and w1118) raised at 16, 22, 24, and 28°C resulted in larger adult body and wing size with lower temperature, while eye size was less affected. The increase in wing size reflected an increase in cell size in both males and females of both stocks. The nucleus size, genome size, and DNA condensation of adult flies, embryos, and Schneider 2 cells (S2 cells, of larval origin) were estimated by flow cytometry. In both adult flies and S2 cells, both nucleus size and DNA condensation varied with temperature, while DNA content appears to be constant. From 12% to 18% of the somatic cells were tetraploid (4C) and 2–5% were octoploid (8C), and for the Oregon strain we observed an increase in the fraction of polyploid cells with decreasing temperature. The observed increase in body size (and wing size) at low temperatures could partly be linked with the cell size and DNA condensation, while corresponding changes in the haploid genome size were not observed.

The roles of juvenile hormone, insulin/target of rapamycin, and ecydsone signaling in regulating body size in Drosophila

Understanding how organisms regulate their body size has interested biologists for decades. Recent work has shown that both insulin/target of rapamycin (TOR) signaling and the steroid hormone ecdysone act to regulate rates of growth and the duration of the growth period in the fruit fly, Drosophila melanogaster. Our recent work has uncovered a third level of interaction, whereby juvenile hormone (JH) regulates levels of both ecdysone and insulin/TOR signaling to control growth rates. These studies highlight a complex network of interactions involved in regulating body and organ size.

Bantam miRNA Promotes Systemic Growth by Connecting Insulin Signaling and Ecdysone Production

During the development of multicellular organisms, body growth is controlled at the scale of the organism by the activity of long-range signaling molecules, mostly hormones. These systemic factors coordinate growth between developing tissues and act as relays to adjust body growth in response to environmental changes [1]. In target organs, long-range signals act in concert with tissue-autonomous ones to regulate the final size of a given tissue. In Drosophila, the steroid hormone ecdysone plays a dual role: peaks of secretion promote developmental transitions and maturation, while basal production negatively controls the speed of growth. The antagonistic action of ecdysone and the conserved insulin/insulin growth factor (IGF) signaling pathway regulate systemic growth and modulate final body size [2, 3]. Here we unravel an unexpected role of bantam microRNA in controlling body size in Drosophila. Our data unveil that, in addition to its well-characterized function in autonomously inducing tissue growth [4-9], bantam activity in ecdysone-producing cells promotes systemic growth by repressing ecdysone release. We also provide evidence that the regulation of ecdysone production by insulin signaling relies on the repression of bantam activity. These results identify a molecular mechanism that underlies the crosstalk between these two hormones and add a new layer of complexity to the well-characterized role of bantam in growth control.

Controlling animal growth and body size – does fruit fly physiology point the way?

The question of how growth and size are controlled has fascinated generations of biologists. However, the underlying mechanisms still remain unclear. The last year or so has seen a flurry of reports on the control of growth and body size in Drosophila, and a central theme to these papers is the idea of signaling between organs as a control mechanism for overall body growth and development. While this concept is obviously not new, these fly studies now open up the possibility of using a genetically tractable system to dissect in detail how organ-to-organ communication dictates body size.

Conserved MicroRNA miR-8/miR-200 and Its Target USH/FOG2 Control Growth by Regulating PI3K

How body size is determined is a long-standing question in biology, yet its regulatory mechanisms remain largely unknown. Here, we find that a conserved microRNA miR-8 and its target, USH, regulate body size in Drosophila. miR-8 null flies are smaller in size and defective in insulin signaling in fat body that is the fly counterpart of liver and adipose tissue. Fat body-specific expression and clonal analyses reveal that miR-8 activates PI3K, thereby promoting fat cell growth cell-autonomously and enhancing organismal growth non-cell-autonomously. Comparative analyses identify USH and its human homolog, FOG2, as the targets of fly miR-8 and human miR-200, respectively. USH/FOG2 inhibits PI3K activity, suppressing cell growth in both flies and humans. FOG2 directly binds to p85alpha, the regulatory subunit of PI3K, and interferes with the formation of a PI3K complex. Our study identifies two novel regulators of insulin signaling, miR-8/miR-200 and USH/FOG2, and suggests their roles in adolescent growth, aging, and cancer.

Size Matters (but So Does Time), and It's OK to Be Different

In this issue of Developmental Cell, Layalle et al. reveal new insights into how nutrition controls body size in Drosophila. Nutrition specifically affects the activity of target of rapamycin (TOR) in the prothoracic gland. Under low-nutrition conditions, TOR suppresses ecdysone secretion--which otherwise terminates larval development--thereby prolonging growth and allowing larvae to still attain a near-normal body size.

Identification of co-regulated transcripts affecting male body size in Drosophila

Factor analysis is applied to microarray data in order to relate gene networks to complex traits and identifies a factor associated with body size in Drosophila simulans.

Genetic architecture and evolutionary constraint when the environment contains genes.

The environment provided by conspecifics is often the most important component of the environment experienced by individuals, frequently having profound effects on fitness and trait expression. Although these social effects on fitness and trait expression may appear to be purely environmental, they differ from other sorts of environmental influences, because they can have a genetic basis and thus can contribute to evolution. Theory has shown that these effects modify the definition of genetic architecture by making the phenotype the property of the genotypes of multiple individuals and alter evolutionary dynamics by introducing additional heritable components contributing to trait evolution. These effects suggest that genetic and evolutionary analyses of traits influenced by social environments must incorporate the genetic components of variation contributed by these environments. However, empirical studies incorporating these effects are generally lacking. In this paper, I quantify the contribution of genetically based environmental effects arising from social interactions during group rearing to the quantitative genetics of body size in Drosophila melanogaster. The results demonstrate that the genetic architecture of body size contains an important component of variation contributed by the social environment, which is hidden to ordinary genetic analyses and opposes the direct effects of genes on body-size development within a population. Using a model of trait evolution, I show that these effects significantly alter evolutionary predictions by providing hidden constraints on phenotypic evolution. The importance of relatedness of interactants and the potential impact of kin selection on the evolution of body size are also examined.

Genetic variance in temperature dependent adult size deriving from physiological genetic variation at temperature boundaries.

An increase in genetic variation in body size has often been observed under stress; an increase in dominance variance and interaction variance as well as in additive genetic variance has been reported. The increase in genetic variation must be caused by physiological mechanisms that are specific to adverse environments. A model is proposed to explain the occurrence of an increase in genetic variation in body size in Drosophila at extreme temperatures. The model has parameters specific to the low- and high-temperature regions of the viable range. Additive genetic variation in the boundary temperatures leads to a marked increase in additive genetic variation in development rate and body size at extreme temperatures. Additive genetic variation in the temperature sensitivity in the low- and high-temperature regions adds non-additive genetic variation. Development rate shows patterns in additive genetic variation that differ from the patterns of genetic variation in body size; therefore, the genetic correlation between development rate and body size changes sign repeatedly as a function of temperature. The existence of dominance in the genetic variation in the boundary temperatures or in the low- and high-temperature sensitivities leads to a higher total genetic variance due to higher dominance and interaction variance, for both development rate and body size.

Quantitative genetic analysis of the body size and shape of Drosophila buzzatii

Body size in Drosophila is known to be closely related to a number of traits with important life history consequences, such as fecundity, dispersal ability and mating success. We examine the quantitative genetic basis of body size in three populations of the cactophilic species Drosophila buzzatii, which inhabit climatically different areas of Australia. Flies were reared individually to eliminate any common environmental component in a full-sib design with families split between two temperatures (18° and 25 °C). The means of several size measures differ significantly among populations while the genetic correlations among these traits generally do not differ, either among populations from different natural environments or between the different laboratory temperatures. This stability of correlation structure is necessary if laboratory estimates of genetic correlations are to have any connection with the expression of genetic variation in the field. The amount of variance due to genotype-by-environment interactions (family x temperature of development) varied among populations, apparently in parallel with the magnitudes of seasonal and diurnal variation in temperature experienced by the different populations. A coastal population, inhabiting a relatively thermally benign environment, showed no interaction, while two inland populations, inhabiting thermally more extreme areas, showed interaction. This interaction term is a measure of the amount of genetic variation in the degree of phenotypic plasticity of body size in response to temperature of development. Thus the inland flies vary in their ability to attain a given body size at a particular temperature while the coastal flies do not. This phenotypic plasticity is shown to be due primarily to differences among genotypes in the amount of response to the change in temperature. A possible selective basis for the maintenance of genetic variation for the levels of phenotypic plasticity is proposed.

Development Rates and the Optimal Body Size in Drosophila: A Reply to Ricklefs

Previous articleNext article No AccessNotes and CommentsDevelopment Rates and the Optimal Body Size in Drosophila: A Reply to RicklefsDerek A. RoffDerek A. Roff Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The American Naturalist Volume 122, Number 4Oct., 1983 Published for The American Society of Naturalists Article DOIhttps://doi.org/10.1086/284158 Views: 3Total views on this site Citations: 2Citations are reported from Crossref Copyright 1983 The University of ChicagoPDF download Crossref reports the following articles citing this article:Jin Yoshimura, William M. Shields PROBABILISTIC OPTIMIZATION OF BODY SIZE: A DISCREPANCY BETWEEN GENETIC AND PHENOTYPIC OPTIMA, Evolution 49, no.22 (May 2017): 375–378.https://doi.org/10.1111/j.1558-5646.1995.tb02250.xWILLIAM T. STARMER, LARRY L. WOLF Causes of variation in wing loading among Drosophila species, Biological Journal of the Linnean Society 37, no.33 (May 2009): 247–261.https://doi.org/10.1111/j.1095-8312.1989.tb01903.x

A Comment on the Optimization of Body Size in Drosophila According to Roff's Life History Model

Previous articleNext article No AccessNotes and CommentsA Comment on the Optimization of Body Size in Drosophila According to Roff's Life History ModelRobert E. RicklefsRobert E. Ricklefs Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The American Naturalist Volume 120, Number 5Nov., 1982 Published for The American Society of Naturalists Article DOIhttps://doi.org/10.1086/284020 Views: 2Total views on this site Citations: 4Citations are reported from Crossref Copyright 1982 The University of ChicagoPDF download Crossref reports the following articles citing this article:Jin Yoshimura, William M. Shields PROBABILISTIC OPTIMIZATION OF BODY SIZE: A DISCREPANCY BETWEEN GENETIC AND PHENOTYPIC OPTIMA, Evolution 49, no.22 (May 2017): 375–378.https://doi.org/10.1111/j.1558-5646.1995.tb02250.xWILLIAM T. STARMER, LARRY L. WOLF Causes of variation in wing loading among Drosophila species, Biological Journal of the Linnean Society 37, no.33 (May 2009): 247–261.https://doi.org/10.1111/j.1095-8312.1989.tb01903.xJan Kozłowski, Richard G. Wiegert Optimal allocation of energy to growth and reproduction, Theoretical Population Biology 29, no.11 (Feb 1986): 16–37.https://doi.org/10.1016/0040-5809(86)90003-1 Derek A. Roff Development Rates and the Optimal Body Size in Drosophila: A Reply to Ricklefs, The American Naturalist 122, no.44 (Oct 2015): 570–575.https://doi.org/10.1086/284158

The effects of disruptive and stabilizing selection on body size inDrosophila melanogaster. III. Genetic analysis of two lines with different reactions to disruptive selection with mating of opposite extremes

A genetic analysis was made of two lines which when subjected to disruptive selection with compulsary mating of opposite extremes (D−) showed a different response viz. one, D−-1, showing predominantly an increase of environmental variance and possibly interaction variance, the other, D−-2, showing an increase of genetic variance. Crosses between extreme flies within lines revealed that D−-1 genomes from large flies are dominant to genomes from small individuals. In D−-2 the genetic variation is predominantly additive variance. Tests for dominant chromosome effect in crosses with an inbred stock with recessive markers showed clear third chromosome differences in D−-2 and not in D−-1. Chromosome exchange between extreme flies corroborated the importance of genetic differences in D−-2. A factor or complex of factors with large effect decreasing body size is located on third chromosomes from small flies in D−-2. Interaction between chromosomes has a similar magnitude in the two lines. Crowding and temperature experiments did not reveal an increased general sensitivity to environmental factors in D−-1, which was suggested by the enlarged environmental variance of this line.

Further evidence for coadaptation in crosses between geographic populations of Drosophila pseudoobscura.

Body size inDrosophila pseudoobscurais a continuously varying character with a high heritability; it is almost certainly related to fitness. Natural populations ofD. pseudoobscurafrom Canada to Mexico have been sampled and found to vary geographically in body size. The geographic variation for the genes determining size is to some extent correlated with the physiographic division of the West. The populations from the Pacific coast have genetically smaller flies than do those from the interior provinces. Experimental populations derived from the samples of seven widely separated natural populations were crossed to yieldF1andF2hybrid generations. Body size in theF1's varied irregularly, while theF2's showed a consistent ‘breakdown’, theF2's being significantly smaller than theirF1parents. TheF1's were significantly less variable than their parents, while theF2's were significantly more variable than their parents of theF1generation. The natural populations possess coadapted genetic systems, with genes mutually adjusted by selection for favorable interactions. Recombination disrupted the balanced genic complexes to give theF2breakdown and the increasedF2variability.D. pseudoobscuradiffers fromD. subobscurain showing the effects expected in crosses between coadapted systems. This species difference lends additional support to the hypothesis that the gene pools of these two successful species respond in different ways to environmental variation. The gene pool ofD. pseudoobscurais flexible and changes readily, while that ofD. subobscurais relatively rigid.

STUDIES IN QUANTITATIVE INHERITANCE. XII. CELL SIZE AND NUMBER IN RELATION TO GENETIC AND ENVIRONMENTAL VARIATION OF BODY SIZE IN DROSOPHILA

STUDIES IN QUANTITATIVE INHERITANCE. XII. CELL SIZE AND NUMBER IN RELATION TO GENETIC AND ENVIRONMENTAL VARIATION OF BODY SIZE IN DROSOPHILA