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PubMed2002

Unsteady aerodynamic force generation by a model fruit fly wing in flapping motion.

A computational fluid-dynamic analysis was conducted to study the unsteady aerodynamics of a model fruit fly wing. The wing performs an idealized flapping motion that emulates the wing motion of a fruit fly in normal hovering flight. The Navier-Stokes equations are solved numerically. The solution provides the flow and pressure fields, from which the aerodynamic forces and vorticity wake structure are obtained. Insights into the unsteady aerodynamic force generation process are gained from the force and flow-structure information. Considerable lift can be produced when the majority of the wing rotation is conducted near the end of a stroke or wing rotation precedes stroke reversal (rotation advanced), and the mean lift coefficient can be more than twice the quasi-steady value. Three mechanisms are responsible for the large lift: the rapid acceleration of the wing at the beginning of a stroke, the absence of stall during the stroke and the fast pitching-up rotation of the wing near the end of the stroke. When half the wing rotation is conducted near the end of a stroke and half at the beginning of the next stroke (symmetrical rotation), the lift at the beginning and near the end of a stroke becomes smaller because the effects of the first and third mechanisms above are reduced. The mean lift coefficient is smaller than that of the rotation-advanced case, but is still 80 % larger than the quasi-steady value. When the majority of the rotation is delayed until the beginning of the next stroke (rotation delayed), the lift at the beginning and near the end of a stroke becomes very small or even negative because the effect of the first mechanism above is cancelled and the third mechanism does not apply in this case. The mean lift coefficient is much smaller than in the other two cases.

Animals↗

PubMed2006

Epidermal growth factor receptor and transforming growth factor-beta signaling contributes to variation for wing shape in Drosophila melanogaster.

Wing development in Drosophila is a common model system for the dissection of genetic networks and their roles during development. In particular, the RTK and TGF-beta regulatory networks appear to be involved with numerous aspects of wing development, including patterning, cell determination, growth, proliferation, and survival in the developing imaginal wing disc. However, little is known as to how subtle changes in the function of these genes may contribute to quantitative variation for wing shape, per se. In this study 50 insertional mutations, representing 43 loci in the RTK, Hedgehog, TGF-beta pathways, and their genetically interacting factors were used to study the role of these networks on wing shape. To concurrently examine how genetic background modulates the effects of the mutation, each insertion was introgressed into two wild-type genetic backgrounds. Using geometric morphometric methods, it is shown that the majority of these mutations have profound effects on shape but not size of the wing when measured as heterozygotes. To examine the relationships between how each mutation affects wing shape hierarchical clustering was used. Unlike previous observations of environmental canalization, these mutations did not generally increase within-line variation relative to their wild-type counterparts. These results provide an entry point into the genetics of wing shape and are discussed within the framework of the dissection of complex phenotypes.

Animals↗

PubMed1990

On the use of excision repair defective cells in the wing somatic mutation and recombination test in Drosophila melanogaster.

Ten chemical mutagens were tested in the wing somatic mutation and recombination test in Drosophila melanogaster. This assay makes use of genetic markers expressed on the wing of adult flies. Larvae which are trans-heterozygous for mwh (multiple wing hairs) and flr (flare) were fed with the compounds either acutely (2, 4, or 6 hr) or chronically (48 or 72 hr), or were treated by inhalation (1 hr). Genetic changes induced in the somatic cells of the wing imaginal discs lead to the formation of mutant clones on the wing (mwh and/or flr). Single spots are produced by point mutation, chromosome breakage, and mitotic recombination; twin spots are produced exclusively by mitotic recombination. All 10 mutagens belonging to different chemical classes were clearly positive in this assay. However, the choice of the optimal treatment conditions (concentration of compound, duration of treatment, age of larvae at treatment) is essential. Eight of the compounds were also tested in excision repair defective cells by introducing the mei-9L1 mutation into the test system. This seems not to improve the detection capacity of the assay, mainly because only small spots are found in excision repair defective wings. In addition, the frequencies of spots in these wings are enhanced four to five times, which makes the scoring more tedious. For these and other practical reasons the use of this specific cross is not recommended in the wing spot test for routine screening purposes.

Animals↗

PubMed1996

Residues of organochlorines in mallards and blue-winged teal collected in Colombia and Wisconsin, 1984-1989.

We compared the seasonal concentrations of 12 organochlorine (OC) compounds in samples of breast muscle, associated skin, and subcutaneous fat of blue-winged teal (Anas discors) collected in Ciénaga Grande de Santa Marta, Colombia (1987-1988), and of mallards (Anas platyrhynchos) and blue-winged teal collected in Wisconsin (1984-1989). Although these species have similar feeding habits and overlapping breeding distributions, their winter ranges differ markedly. Most blue-winged teal winter in the Neotropics, whereas most mallards remain in the temperate regions of North America. A seasonal comparison of OC exposure in these species may help determine the geographic origins of contamination. All examined OCs were found to be below concentrations known to affect reproduction in waterfowl. DDE was most often detected in blue-winged teal and PCBs, in mallards. DDE exposure may have predominantly occurred outside of Wisconsin. The DDE concentration in blue-winged teal samples collected in Wisconsin in the spring (GM=0.406 microg/g) were greater (P<0.001) than in the fall (GM=0. 033 microg/g) and greater than the concentrations in mallard samples from the spring (GM=0.058 microg/g; P<0.001). Ciénaga Grande, however, was not a source of DDE contamination. The DDE concentrations in blue-winged teal samples from Ciénaga Grande did not differ between the spring (GM=0.037 microg/g) and the fall (GM=0. 039 microg/g) and were lower (P<0.001) than the concentration in blue-winged teal samples from Wisconsin in the spring. In contrast, PCB contamination seemed to have occurred in Wisconsin and affected mostly mallards. PCBs were not detected in the samples from Colombia and were detected in only five (8.3%) of the blue-winged teal samples from Wisconsin (GM=0.025 microg/g), however, those compounds were detected in 47% of the mallard samples collected in Wisconsin (GM=0.272 microg/g). DDE and PCB concentrations were greater (P=0.0) in mallard samples collected from wetlands adjacent to Lake Michigan than in samples from inland wetlands.

Adipose Tissue↗

PubMed2000

Juvenile hormone titer and morph-specific reproduction in the wing-polymorphic cricket, Gryllus firmus.

Juvenile hormone titers and reproductive characteristics were measured in adult wing and flight-muscle morphs of the wing-polymorphic cricket, Gryllus firmus, during the first week of adulthood. This species has three morphs: one flight capable morph with fully-developed wings and fully-developed flight muscles [LW(F)], one flightless morph with fully-developed wings and histolyzed (non-functional) flight muscles [LW(H)], and another flightless morph with underdeveloped (short) wings and underdeveloped flight muscles (SW). Both flightless morphs [LW(H) and SW] had larger ovaries which contained a greater number of postvitellogenic eggs compared with the flight capable [LW(F)] morph. The juvenile hormone titer was significantly higher in SW compared with LW(F) females on days 3-7 of adulthood. On these days, the JH titer also was significantly higher in the other flightless morph, LW(H), compared with flight-capable [LW(F)] females as determined by one statistical test, but did not differ significantly by another test. The JH titer was positively correlated with ovarian mass or terminal oocyte length, but not with the number of post-vitellogenic eggs. This study is the first direct comparison of juvenile hormone titers in adult wing morphs of a wing-polymorphic insect. Results indicate that an elevated juvenile hormone titer may be at least partly responsible for one of the most distinctive features of wing-polymorphic species, the increased early fecundity of flightless females.

Journal Article↗

PubMed1997

Iliac wing angle as a marker for trisomy 21 in the second trimester.

OBJECTIVE: To evaluate the fetal iliac wing angle in detecting trisomy 21 in the second trimester of pregnancy. METHODS: Using an axial view of the fetal pelvis, the angle between the right and left iliac wings (iliac wing angle) was measured ultrasonographically at the time of the second-trimester ultrasound or genetic amniocentesis in 377 singleton fetuses. Trisomy 21 was diagnosed by karyotype results from the amniocentesis or newborn examination with karyotype if trisomy 21 was suspected based on phenotypic features. Sensitivity, specificity, and positive (PPV) and negative predictive values (NPV) were calculated using multiple cutoff points. A receiver operating characteristic (ROC) curve was used to identify the optimum iliac wing angle. Descriptive statistics and Student t test were utilized for analyses with a P of less than .05 considered significant. RESULTS: The average gestational age was 18.8 weeks (range 13-32). Karyotypes were available in 128 fetuses. The overall prevalence of trisomy 21 was 11 of 377 (2.9%). The mean (+/-standard deviation) iliac wing angle in the normal fetuses was 68.2 degrees (+/-15.4 degrees) and 98.5 degrees (+/-11.3 degrees) in fetuses with trisomy 21 (P < .001). Using an ROC-derived absolute cutoff of 90 degrees, an abnormal iliac wing angle had sensitivity of 90.9% (ten of 11), specificity of 94.5% (346 of 366), NPV of 99.7% (346 of 347), and PPV of 33.3% (ten of 30) to detect trisomy 21. CONCLUSION: Fetuses with trisomy 21 have greater iliac wing angles than do normal fetuses. Using an ROC-derived absolute cutoff of 90 degrees, we could detect 90.9% of fetuses with trisomy 21 with a PPV of 33% in our high-risk population. These findings suggest that iliac wing angle is a useful marker in antenatal screening for trisomy 21.

Adolescent↗

PubMed1990

Selection on wing allometry in Drosophila melanogaster.

Five bivariate distributions of wing dimensions of Drosophila melanogaster were measured, in flies 1) subjected to four defined environmental regimes during development, 2) taken directly from nature in seven U.S. states, 3) selected in ten populations for change in wing form, and 4) sampled from 21 long inbred wild-type lines. Environmental stresses during development altered both wing size and the ratios of wing dimensions, but regardless of treatment all wing dimensions fell near a common allometric baseline in each bivariate distribution. The wings of wild-caught flies from seven widely separated localities, and of their laboratory-reared offspring, also fell along the same baselines. However, when flies were selected divergently for lateral offset from these developmental baselines, response to selection was rapid in every case. The mean divergence in offset between oppositely selected lines was 14.68 SD of the base population offset, after only 15 generations of selection at 20%. Measurements of 21 isofemale lines, founded from wild-caught flies and maintained in small populations for at least 22 years, showed large reductions in phenotypic variance of offsets within lines, but a large increase in the variance among lines. The variance of means of isofemale lines within collection localities was ten times the variance of means among localities of newly established wild lines. These observations show that much additive genetic variance exists for individual dimensions within the wing, such that bivariate developmental patterns can be changed in any direction by selection or by drift. The relative invariance of the allometric baselines of wing morphology in nature is most easily explained as the result of continuous natural selection around a local optimum of functional design.

Animals↗

PubMed2001

The wing in yeast heat shock transcription factor (HSF) DNA-binding domain is required for full activity.

The yeast heat shock transcription factor (HSF) belongs to the winged helix family of proteins. HSF binds DNA as a trimer, and additional trimers can bind DNA co-operatively. Unlike other winged helix-turn-helix proteins, HSF's wing does not appear to contact DNA, as based on a previously solved crystal structure. Instead, the structure implies that the wing is involved in protein-protein interactions, possibly within a trimer or between adjacent trimers. To understand the function of the wing in the HSF DNA-binding domain, a Saccharomyces cerevisiae strain was created that expresses a wingless HSF protein. This strain grows normally at 30 degrees C, but shows a decrease in reporter gene expression during constitutive and heat-shocked conditions. Removal of the wing does not affect the stability or trimeric nature of a protein fragment containing the DNA-binding and trimerization domains. Removal of the wing does result in a decrease in DNA-binding affinity. This defect was mainly observed in the ability to form the first trimer-bound complex, as the formation of larger complexes is unaffected by the deletion. Our results suggest that the wing is not involved in the highly co-operative nature of HSF binding, but may be important in stabilizing the first trimer bound to DNA.

Amino Acid Motifs↗

PubMed1994

THE EFFECTS OF WING ROTATION ON UNSTEADY AERODYNAMIC PERFORMANCE AT LOW REYNOLDS NUMBERS

The downstroke-to-upstroke transition of many insects is characterized by rapid wing rotation. The aerodynamic consequences of these rapid changes in angle of attack have been investigated using a mechanical model dynamically scaled to the Reynolds number appropriate for the flight of small insects such as Drosophila. Several kinematic parameters of the wing flip were examined, including the speed and axis of rotation, as well as the duration and angle of attack during the wing stroke preceding rotation. Alteration of these kinematic parameters altered force generation during the subsequent stroke in a variety of ways. 1. When the rotational axis was close to the trailing edge, the model wing could capture vorticity generated during rotation and greatly increase aerodynamic performance. This vortex capture was most clearly manifested by the generation of lift at an angle of attack of 0°. Lift at a 0° angle of attack was also generated following rotation about the leading edge, but only if the downstroke angle was large enough to generate a von Karman street. The lift may be due to an alteration in the effective angle of attack caused by the inter-vortex stream in the downstroke wake. 2. The maximum lift attained (over all angles of attack) was substantially elevated if the wing translated backwards through a wake generated by the previous stroke. Transient lift coefficient values of nearly 4 were obtained when the wing translated back through a von Karman street generated at a 76.5° angle of attack. This effect might also be explained by the influence of the inter-vortex stream, which contributes a small component to fluid velocity in the direction of translation. 3. The growth of lift with angle of attack was significantly elevated following a 7.5 chord stroke with a 76.5° angle of attack, although it was relatively constant under all other kinematic conditions. 4. The results also indicate the discrepancies between transient and time-averaged measures of performance that arise when unsteady mechanisms are responsible for force generation. Although the influence of wing rotation was strong during the first few chords of translation, averaging the performance over as little as 6.5 chords of motion greatly attenuated the effects of rotation. 5. Together, these modeling results suggest that the unsteady mechanisms generated by simple wing flips could provide an important source for the production of aerodynamic forces in insect flight. Furthermore, the extreme sensitivity to small variations in almost all kinematic parameters could provide a foundation for understanding the aerodynamic mechanisms underlying active flight control.

Journal Article↗

PubMed2026

Comparative genomics and full-length transcriptome profiling of wing morphs in Tetrix grossus (Orthoptera: Tetrigidae).

Wing polymorphism represents a paradigmatic dispersal-reproduction trade-off, yet its molecular basis remains uncharacterised in the phylogenetically distant pygmy grasshoppers (Tetrigidae). Here we integrate comparative genomics across ten orthopteran species with full-length transcriptomics of long-winged (FL) and short-winged (FS) Tetrix grossus. OrthoFinder recovered 118 orthogroups specific to T. grossus. Against a backdrop of pronounced gene-family contraction (36 expansions versus 222 contractions; net -186, mirrored at the ancestral Tetrix node, +37/-140), we identified an ancestral, Tetrix-specific expansion of hormone-regulation (12 genes; fold enrichment 7.93) and lipid/carbohydrate-metabolic families organised into syntenic clusters, alongside 513 positively selected genes enriched for integrin-mediated cell adhesion (6 genes), a process relevant to epithelial and appendage morphogenesis. Full-length transcriptomics of one long-winged (FL) and one short-winged (FS) adult female detected 7530 (FL) and 7515 (FS) expressed genes, with 794 FL- and 776 FS-restricted transcriptome-derived SNP-associated genes. The FL morph was enriched for an EGFR/Ras-Rho developmental-patterning axis and neuromuscular flight genes, whereas the FS morph was enriched for insulin/peptide-hormone response and growth-regulatory loci. Overall, we present genomic resources and testable hypotheses concerning the evolution and regulation of wing morphs in Tetrigidae rather than a validated genetic architecture of wing-morph determination.

Animals↗

PubMed1996

Engrailed gene dosage determines whether certain recessive cubitus interruptus alleles exhibit dominance of the adult wing phenotype in Drosophila.

The cubitus interruptus (ci) locus of Drosophila melanogaster is needed for normal development. Some mutants of this gene result in embryonic lethality, while others just disrupt adult wing veins. While undertaking a genetic screen for additional ci mutations that affect the wing veins, we recovered a modifier mutation on chromosome two that produced a ci phenotype in recessive ci heterozygotes (ci(recessive)/+). We identified the modifier mutation as an allele of engrailed and have called it engrailed-enhancer of cubitus interruptus (enEnci). As a double heterozygote (en-/+; ci-/+) this new en allele dominantly generates a ci wing vein phenotype. As a double heterozygote, it also enhances the ci wing vein phenotype of the dominant alleles ciW and ciCe2, but not ciD. Other loss-of-function en alleles also enhance the ci phenotype, with the en lethal alleles (and deletions) showing the strongest effect, while the homozygous viable en alleles show weaker enhancement. Strong en- alleles failed to induce a ci phenotype with heterozygotes of ci recessive lethal alleles l(4)13, l(4)17, or ciDrev, which are loss-of-function mutations. This supports a previous proposal that the ci wing vein phenotype is not due to loss of ci+ function, as would be expected for most recessive alleles. Instead, the adult wing vein abnormality is due to ectopic expression (or de-repression) of the ci transcript in the posterior compartment of the wing disc. We also observed that en-/+ heterozygotes could induce a ci phenotype in situations where the ci+ locus is either unpaired or hemizygous. Since loss of one en+ gene dose enhanced the ci phenotype, three doses of en+ were tested and found to suppress expression of the ci phenotype in ci1 homozygotes and ciW heterozygotes. These observations show that correct regulation of the ci gene involves more than the simple interaction of upstream regulatory elements. some pairing, pairing dependent gene repression, position effects.

Alleles↗

PubMed1993

Evaluation of the chick wing territory as an equipotential self-differentiating system.

Harrison (1918: J. Exp. Zool. 25: 413-461) described a developmental field as an "equipotential self-differentiating system." The present study was undertaken to address the question: To what extent can be pre-limb territory of a chick embryo be considered a developmental field? To what extent is the chick pre-limb territory an equipotential self-differentiating system? Two sets of experiments were undertaken to address these questions: (1) Whole and half limb territories were explanted to the celoma of host embryos, and (2) portions of the wing territories were extirpated. The wing exhibited the quality of self-differentiation after stage 12, in that the isolated wing territory, grafted to a host celom, could form limbs beginning at stage 12 (however, complete wings formed only from wing territories of stage 16 and older). On the other hand, the chick wing territory did not appear to exhibit equipotentiality. No posterior half limb graft formed normal limbs, and only in two exceptional cases did anterior half limb grafts form limbs. If part or all of the wing territory was removed from chick embryos, normal limbs formed in less than 15% of the cases after stage 15, in about 30% of the cases at stages 13 and 14, but in over half the cases at stages 10-12. Wound healing and reinitiation of limb potential may be responsible for the higher incidence of limb formation at the younger ages.

Animals↗

PubMed2005

Drosophila Lipid Storage Droplet 2 gene (Lsd-2) is expressed and controls lipid storage in wing imaginal discs.

Lipid droplets are the major neutral lipid storage organelles in higher eukaryotes. The PAT domain proteins (Perilipin, ADRP [adipose differentiation related protein], and TIP47 [tail-interacting 47-kDa protein]) are associated with these structures. Perilipin and ADRP are involved in the regulation of lipid storage and metabolism in mammals. Two genes encoding PAT proteins, Drosophila Lipid Storage Droplet 2 Gene (Lsd-2) and Lsd-2, have been identified in Drosophila. Lsd-2 is expressed in fat bodies and in the female germ line and is involved in lipid storage in these tissues. We showed that Lsd-2 is expressed in third-instar wing imaginal discs in Drosophila, with higher levels in the wing pouch, which corresponds to the presumptive wing region of the wing disc. This specific expression pattern is correlated with a high level of neutral lipid accumulation. We also showed that neutral lipid deposition in the wing disc is severely reduced in an Lsd-2 mutant and is increased with Lsd-2 overexpression. Finally, we showed that overexpression of the vestigial (vg) pro-wing gene induces Lsd-2 expression, suggesting that Lsd-2 mediates a vg role during wing formation. Our results suggest that Lsd-2 function is not restricted to tissues directly involved in lipid storage and could play additional roles during development.

Animals↗

PubMed2003

Wing-locking mechanisms in aquatic Heteroptera.

This account provides a detailed morphological and ultrastructural study of wing-locking mechanisms (LM) in some aquatic Heteroptera. Scanning and transmission electron microscopy were used to describe the functional significance of macro- and microstructures holding wings tightly against the body at rest and those involved in functional diptery in flight. There are two types of LM holding the forewings (hemelytra) at rest: 1) wing-to-wing LM, and 2) wing-to-body LM. The first type includes the brush-to-brush LM, the clavus-clavus clamp and the clavus-clavus locking ridge. The second type includes devices locking the hemelytra to the body: the subcostal border of the hemelytra to the lateral border of mesepimeron, the knob-and-socket locking mechanism of the hemelytra, and the clavus-locking mechanism to the scutellum groove. The hindwing is locked by a pair of microtrichial fields situated on the hindwing-articulated pad at the basal area of the hindwing and on the thoracic pad in the vicinity of the wing articulation. Morphological and ultrastructural data suggest that different LM are parts of one mechanism holding wings to the body at rest. An additional locking mechanism, connecting the hemelytra with the hindwing, is the only LM providing functional diptery in flight.

Adaptation, Biological↗

PubMed1994

A role for the segment polarity gene shaggy-zeste white 3 in the specification of regional identity in the developing wing of Drosophila.

The Drosophila segment polarity gene known as shaggy or zeste white 3 encodes a ubiquitously expressed serine-threonine protein kinase which is critical for a number of important developmental processes. In the developing wing blade, clones of cells lacking the normal shaggy-zeste white 3 product form dense tufts of margin-like bristles and bristle precursors. In a previous study I hypothesized that this phenotype could be best explained as a transformation in the regional identity of wing blade cells to one resembling that found along the normal wing margin. A number of genes have recently been identified which are expressed exclusively or at higher levels along the normal wing margin; in this study I will show that two of these genes, vestigial and scalloped, are overexpressed at margin-like levels in shaggy-zeste white 3 clones. This phenotype does not depend upon the formation of ectopic bristle precursors and occurs in clones lacking both shaggy-zeste white 3 and the entire achaete-scute complex. As vestigial and scalloped are both involved in early patterning events prior to the stages of bristle specification, these results strongly suggest that shaggy-zeste white 3 is required for the normal specification or maintenance of regional identity in the developing wing blade. The margin-like transformation is, however, partial, since the expression of apterous (in pupal wings) and wingless and cut (at late third instar) was not reliably altered in shaggy-zeste white 3 clones. It has been suggested that shaggy-zeste white 3 is involved in a wingless signaling pathway in the embryo; a model is discussed in which shaggy-zeste white 3 acts downstream of localized apterous and wingless expression to specify or maintain margin identity in the wing.

Animals↗

PubMed1996

decapentaplegic overexpression affects Drosophila wing and leg imaginal disc development and wingless expression.

We have used the GAL4-UAS expression system to increase the level of expression of the Drosophila gene decapentaplegic (dpp) in a pattern approximating its normal pattern in leg and wing imaginal discs. Intermediate increases of dpp expression have little effect in wing discs but high levels of dpp overexpression lead to reduction of the scutellum and duplication of posterior wing structures. In leg discs intermediate increases cause supernumerary outgrowths of ventral leg structures in the anterior-ventral region. Greater increases of dpp expression cause the loss of ventral leg structures with the concomitant fusion of left and right dorsal forelegs. The defects observed in both legs and wings appear to arise through dose-dependent effects of dpp on wingless (wg) expression. A high level of dpp overexpression in the wing disc causes reduction of wg expression in the presumptive scutellar region, consistent with the subsequent reduction of the scutellum. An intermediate increase of dpp expression in leg discs induces the expansion of wg expression into the ventral outgrowths. At higher dpp expression levels, ventral wg expression in leg discs is eliminated, consistent with the loss of ventral leg cuticle. In the leg disc end knob and in the wing margin primordium, where wg and dpp cooperate in producing distal outgrowth, dpp overexpression has no detectable effect either on patterning or on wg expression. We propose that a critical role for dpp in other regions of the leg and wing discs is to reduce or block the expression of wg. This role of dpp is supported by the observation that ectopic wg expression is detected in imaginal discs where dpp signaling is compromised by lowering the activity of one of its receptors, tkv. This antagonism between dpp and wg expression may be critical to assigning only one disc region as the distal organizer.

Animals↗

PubMed1998

Specific interactions between vestigial and scalloped are required to promote wing tissue proliferation in Drosophila melanogaster.

The two genes vestigial (vg) and scalloped (sd) are required for wing development in Drosophila melanogaster. They present similar patterns of expression in second and third instar wing discs and similar wing mutant phenotypes. vg encodes a nuclear protein without any recognized nucleic acid-binding motif. Sd is a transcription factor homologous to the human TEF-1 factor whose promoter activity depends on cell-specific cofactors. We postulate that Vg could be a cofactor of Sd in the wing morphogenetic process and that, together, they could constitute a functional transcription complex. We investigated genetic interactions between the two genes. We show here that vg and sd co-operate in vivo in a manner dependent on the structure of the Vg protein. We ectopically expressed vg in the patch (ptc) domains. We show evidence that wing-like outgrowths induced by ectopic expression of vg are severely reduced in vg or sd mutant backgrounds. Accordingly, we demonstrate that ptc-GAL4-driven expression of vg induces both expressions of the endogenous vg and sd genes and that the two Vg and Sd proteins have to be produced together to promote wing proliferation. Furthermore, we show an interaction between the two proteins by double hybrid experiments in yeast. Our results therefore support the hypothesis that Sd and Vg directly interact in vivo to form a complex regulating the proliferation of wing tissue.

Animals↗

PubMed2003

The interplay between density- and trait-mediated effects in predator-prey interactions: a case study in aphid wing polymorphism.

Natural enemies not only influence prey density but they can also cause the modification of traits in their victims. While such non-lethal effects can be very important for the dynamic and structure of prey populations, little is known about their interaction with the density-mediated effects of natural enemies. We investigated the relationship between predation rate, prey density and trait modification in two aphid-aphid predator interactions. Pea aphids (Acyrthosiphon pisum, Harris) have been shown to produce winged dispersal morphs in response to the presence of ladybirds or parasitoid natural enemies. This trait modification influences the ability of aphids to disperse and to colonise new habitats, and hence has a bearing on the population dynamics of the prey. In two experiments we examined wing induction in pea aphids as a function of the rate of predation when hoverfly larvae (Episyrphus balteatus) and lacewing larvae (Chrysoperla carnea) were allowed to forage in pea aphid colonies. Both hoverfly and lacewing larvae caused a significant increase in the percentage of winged morphs among offspring compared to control treatments, emphasising that wing induction in the presence of natural enemies is a general response in pea aphids. The percentage of winged offspring was, however, dependent on the rate of predation, with a small effect of predation on aphid wing induction at very high and very low predation rates, and a strong response of aphids at medium predation rates. Aphid wing induction was influenced by the interplay between predation rate and the resultant prey density. Our results suggests that density-mediated and trait-mediated effects of natural enemies are closely connected to each other and jointly determine the effect of natural enemies on prey population dynamics.

Animals↗