Flight Muscle Research Articles

A review on insects flight aerodynamics, noise sources, and flow control mechanisms

Wildlife always acts as an inspiration source for humans to help them study and mimic flight methods. Insects are one of the most important sources of biological systems’ inspiration to control flow and reduce aerodynamic noise. Insects are classified into different kinds, and most can fly by fluttering their wings. In general, insects’ flight muscles are divided into direct and indirect types that act synchronously and asynchronously with nerve impulses, respectively. These muscles help insects use a mixture of rotating, flapping, and pitching movements to achieve specific wing kinematics. Insects use various mechanisms for generating aerodynamic forces, including the Weis-Fogh or clap and fling mechanism, delayed stall due to unsteady motion (Wagner effect), wing rotation (Kramer effect), wake capture or wing–wake interaction, added mass, and absence of stall. On the other hand, the insect noises are divided into aerodynamic and structural. Insects’ aerodynamic noise is created by fluctuating forces, flow–solid interaction, shed vortex, and turbulence inflow. Meanwhile, insects’ structural noise is made by frictional and tymbal mechanisms. Their flow control methods are classified into two categories: wing shape and sub-structures. Wing shape features such as planform, chord length and location, twist, sweep, wingtip, and aspect ratio influence the flow around the insects. The sub-structures such as leading edge, trailing edge, swallowtail, and surface textures affect the flow too. A thorough understanding of insects’ fly, aerodynamic noise, and their control flow techniques will significantly help engineers to produce competitive products with better aerodynamic performance and aeroacoustic signature.

Balanced mitochondrial function at low temperature is linked to cold adaptation in Drosophila species.

The ability of ectothermic animals to live in different thermal environments is closely associated with their capacity to maintain physiological homeostasis across diurnal and seasonal temperature fluctuations. For chill-susceptible insects, such as Drosophila, cold tolerance is tightly linked to ion and water homeostasis obtained through a regulated balance of active and passive transport. Active transport at low temperature requires a constant delivery of ATP and we therefore hypothesize that cold-adapted Drosophila are characterized by superior mitochondrial capacity at low temperature relative to cold-sensitive species. To address this, we investigated how experimental temperatures from 1 to 19 °C affected mitochondrial substrate oxidation in flight muscle of seven Drosophila species and compared it to a measure of species cold tolerance (CTmin, the temperature inducing cold coma). Mitochondrial oxygen consumption rates measured using a substrate-uncoupler-inhibitor-titration (SUIT) protocol showed that cooling generally reduced oxygen consumption of the electron transport system across species, as was expected due to thermodynamic effects. Complex I is the primary consumer of oxygen at non-stressful temperatures, but low temperature decreases complex I respiration to a much greater extent in cold-sensitive species than in cold-adapted species. Accordingly, cold-induced reduction of complex I correlates strongly with CTmin. The relative contribution of other substrates (proline, succinate and glycerol-3-phosphate) increased as temperature decreased, particularly in the cold-sensitive species. At present, it is unclear whether the oxidation of alternative substrates can be used to offset the effects of the temperature-sensitive complex I, and the potential functional consequences of such a substrate switch are discussed.

Changes in mitochondrial function parallel life history transitions between flight and reproduction in wing polymorphic field crickets.

Mitochondria serve as critical producers of both cellular energy and metabolic precursors for biosynthesis required for organismal growth, activity, somatic maintenance, and reproduction. Consequently, variation in mitochondrial function is commonly associated with variation in life histories both within and across species. For instance, flight-capable, long-winged crickets have mitochondria with larger bioenergetic capacities than flightless, short-winged crickets investing in early lifetime fecundity instead of flight. However, we do not know whether differences in mitochondrial function associated with life history are fixed or result from flexible changes in metabolism throughout the life cycle. We measured mitochondrial function of fat body tissue across early adulthood of long-winged and short-winged crickets from two species of wing-polymorphic field crickets (Gryllus firmus and Gryllus lineaticeps). Fat body is a multifunctional organ that supports both flight and reproduction in insects. Consistent with flexibility in mitochondrial function specific for alternative life histories, the capacity for oxidative phosphorylation increases in mitochondria throughout early adulthood in the fat body of long-winged but not short-winged crickets. Furthermore, fat body mitochondrial oxidative phosphorylation capacities declined rapidly when long-wing crickets degraded their flight muscles and initiated large-scale oogenesis. This finding suggests that shifts in tissue function require a concurrent shift in mitochondrial function and that tissue-specific functional constraints may underpin the flight-oogenesis trade-off. In conclusion, changes in mitochondrial bioenergetics form a component of alternative life histories, indicating that mitochondrial function is dynamic and set to a level that matches current and future energy demands and biosynthetic requirements of life history.

Systemic orchestration of cell size throughout the body: influence of sex and rapamycin exposure in Drosophila melanogaster.

Along with differences in life histories, metazoans have also evolved vast differences in cellularity, involving changes in the molecular pathways controlling the cell cycle. The extent to which the signalling network systemically determines cellular composition throughout the body and whether tissue cellularity is organized locally to match tissue-specific functions are unclear. We cultured genetic lines of Drosophila melanogaster on food with and without rapamycin to manipulate the activity of target of rapamycin (TOR)/insulin pathways and evaluate cell-size changes in five types of adult cells: wing and leg epidermal cells, ommatidial cells, indirect flight muscle cells and Malpighian tubule epithelial cells. Rapamycin blocks TOR multiprotein complex 1, reducing cell growth, but this effect has been studied in single cell types. As adults, rapamycin-treated flies had smaller bodies and consistently smaller cells in all tissues. Regardless, females eclosed with larger bodies and larger cells in all tissues than males. Thus, differences in TOR activity and sex were associated with the orchestration of cell size throughout the body, leading to differences in body size. We postulate that the activity of TOR/insulin pathways and their effects on cellularity should be considered when investigating the origin of ecological and evolutionary patterns in life histories.

Blood meal digestion and changes in lipid reserves are associated with the post-ecdysis development of the flight muscle and ovary in young adults of Rhodnius prolixus

Rhodnius prolixus is a hemimetabolous, hematophagous insect, and both nymphs and adults feed exclusively on blood. The blood feeding triggers the molting process and, after five nymphal instar stages, the insect reaches the winged adult form. After the final ecdysis, the young adult still has a lot of blood in the midgut and, thus, we have investigated the changes in protein and lipid contents that are observed in the insect organs as digestion continues after molting. Total midgut protein content decreased during the days after the ecdysis, and digestion was finished fifteen days later. Simultaneously, proteins and triacylglycerols present in the fat body were mobilized, and their contents decreased, whereas they increased in both the ovary and the flight muscle. In order to evaluate the activity of de novo lipogenesis of each organ, the fat body, ovary and flight muscle were incubated in the presence of radiolabeled acetate, and the fat body showed the highest efficiency rate (around 47%) to convert the taken up acetate into lipids. The levels of de novo lipid synthesis in the flight muscle and ovary were very low. When 3H-palmitate was injected into the young females, its incorporation by the flight muscle was higher than by the ovary or the fat body. In the flight muscle, the 3H-palmitate was similarly distributed amongst triacylglycerols, phospholipids, diacylglycerols and free fatty acids, while in the ovary and fat body it was mostly found in triacylglycerols and phospholipids. The flight muscle was not fully developed after the molt, and at day two no lipid droplets were observed. At day five, very small lipid droplets were present, and they increased in size up to day fifteen. The diameter of the muscle fibers also increased from day two to fifteen, as well as the internuclear distance, indicating that muscle hypertrophy occurred along these days. The lipid droplets from the fat body showed a different pattern, and their diameter decreased after day two, but started to increase again at day ten. The data presented herein describes the development of the flight muscle after the final ecdysis, and modifications that occur regarding lipid stores. We show that, after molting, substrates that are present in the midgut and fat body are mobilized and directed to the ovary and flight muscle, for the adults of R. prolixus to be ready to feed and reproduce.

Even the tiniest snapping shrimp claws make cracking pistol pops

When it comes to a quick draw, few creatures outgun adult snapping shrimp (Alpheus heterochaelis). They stun passing fish and foes with a simple click of a spring-loaded claw, which squirts a high-speed jet that rips through the water, producing a vapour-filled bubble (a cavitation bubble) that then implodes, resulting in a catastrophic shock wave – complete with a sharp popping sound and minute flash of light – to incapacitate their opponent. ‘We can't see the bubble with our naked eyes, it happens too fast, but we can hear when the bubble collapses’, says Jacob Harrison (then at Duke University, USA), adding that the adult shrimp's claws crash together at blisteringly fast speeds up to 30 m s−1. The entire process is over in less than a millisecond. But at what point in their growth do snapping shrimp develop their hair trigger claws, when are they capable of squirting a jet that can rip water asunder, and how does their performance compare with that of their parents? While a graduate student in Sheila Patek's Duke University laboratory, Harrison became surrogate parent to a troupe of developing snapping shrimp to find out. After collecting four snapping shrimp females carrying eggs from the mudflats off Beaufort, North Carolina, USA, Harrison nurtured the shrimp youngsters after hatching, keeping track of their growth, until they began snapping their claws at around the age of 1 month. ‘I couldn't see it, but I began to hear it’, says Harrison, who filmed the youngster's claw clicks under a microscope at 300,000 frames s−1 over a 3-week period to capture every detail of the lightning-fast manoeuvre as the crustaceans matured. ‘I had to annoy them with a toothpick, so they would snap’, he chuckles. After filming more than 280 claw snaps, Harrison began painstakingly reconstructing 125 of the manoeuvres to calculate the acceleration of the claws as they crashed closed, the amount of energy used and the power required to produce the water jet.Incredibly, even the tiniest snapping shrimp – with claws that were only 1 mm long, and weighing just 0.03 mg – could occasionally squirt a jet of water producing an explosive cavitation bubble. ‘I was completely ecstatic! This snapping shrimp was about the length of a staple and it could move fast enough to cavitate water’, exclaims Harrison. And when he calculated the acceleration of the minute top claw as it closed down on the lower claw, Harrison was astonished that it was reaching an acceleration of 580,000 m s−2 – as fast as a bullet and ∼20 times faster than the adult's claw – while rotating at more than 1,500,000 deg s−1 (250,000 rpm). ‘It is the fastest recorded acceleration for a repeatable, underwater motion’, says Harrison, although he explains that Dracula ant jaws accelerate faster in air as they slide across each other.Next, Harrison calculated the power required to produce such an impressive explosion, and it came in at ∼65,000,000 W kg−1 of muscle, far exceeding the 1200 W kg−1 measured for the most powerful bird flight muscle. Only a catapult, storing energy and then releasing it instantaneously, could produce such an explosive jet of water.So, snapping shrimp develop the ability to snap their claws closed, producing a cavitation bubble, a little over a month after they hatch, achieving astonishingly fast accelerations that far exceed those of their parents. But Harrison suspects that the youngsters have to fire a few blanks before they build up to producing cavitation bubbles. ‘Juveniles may be “practicing” their strikes’, he suggests, explaining that the youngsters may need to lock and load a few times to build up until they are capable of reliably releasing their ballistic cavitating water jets.

Energy Utilization and Flight Muscle Development in Chrysoperla sinica (Neuroptera: Chrysopidae) Female Adults: Relationship With Age and Flight Behavior.

We investigated the accumulation of energy substances, dynamics of flight muscle development, changes in energy substances accumulation, and flight muscle structure after flight activities in female adults of the green lacewing Chrysoperla sinica (Tjeder), a common natural enemy of various insect pests in China. Virgin individuals were chosen at 24, 72, and 120 h after eclosion for energy substance determination and flight muscle observation in this study. Individuals with strong flight ability at 72 h after eclosion were selected for tethered flight assays, followed by detection of energy substances, and flight muscle observation. The results showed that virgin female adults had the highest fat content 72 h after eclosion. Sarcomere length and myofibril diameter changed significantly with age, with the lowest at 24 h after eclosion. With an increase in flight distance, the fat and glycogen contents, sarcomere length, and volume fraction of the transverse tubular system (T-system) decreased and myofibril diameters increased. The volume fraction of the mitochondria did not significantly change, but the structure of the mitochondrial membrane was destroyed, inclusions were reduced, and cavities appeared. The reserves of energy substances, especially lipids, are closely related to the flight ability of C. sinica. The observational results of both flight muscle structure and morphology of mitochondria build a strong relationship with flight behavior. This research should help reveal the regulatory mechanism of flight activity of C. sinica.

External and Skeletal Morphology of Molossus fluminensis Lataste, 1891 (Chiroptera, Molossidae) with Notes on Quadrupedal Locomotion and Habitat Use

Molossus fluminensis is a species of the wide diversified family Molossidae. Representants of this family have evolved under pressures associated to two different behaviors — a high speed and efficient flight and a good quadrupedal ability. The aim of this study is to describe in detail the morphological characters of M. fluminensis, focusing on its skeletal features, and to point out the main characters that could represent functional responses to the evolution of the quadrupedal ability and habitat use in the group. Furthermore, we aim to contribute to the knowledge of a recently revalidated and cryptic species of Molossus, giving a morphometric characterization for the species and notes on sexual dimorphism. Four adult specimens of M. fluminensis, one male and three females, were prepared as skin and skeleton, and five external and 146 linear measurements of the skeleton were taken. The anatomical characters were described following current literature and included the axial and appendicular skeleton. We found that the male presented greater measurements than females in most linear characters, and had a more developed sagittal and lambdoid crests, while the ischiatic arcade was more caudally projected in females. A narrow rib cage, a long, thin sternum, and a cranially oriented ventral process of manubrium make the M. fluminensis body more compact dorsoventrally without compromising the area of insertion of the flight musculature. These appear to be adaptations for roosting in narrow crevices. The expanded sacral vertebrae, the deep gluteal fossa of the ilium, and the presence of well-developed processes on the first caudal vertebra, point to a greater area for muscle origin in this region, while the well-developed trochanters and ridges of the femur and tibia provide surfaces for muscle attachment. Together, these characteristics point to a great range of movement of the limbs and the tail, important factors during quadrupedal locomotion. The results obtained here may shed light on the evolution of quadrupedalism in molossids and other quadrupedal bats.

Cryo-EM structure of the flight muscle thick filament from the bumble bee, Bombus ignitus, with novel non-myosin densities revealed.

The cryo-EM structure of the flight muscle thick filament of Bombus ignitus (order Hymenoptera) has been resolved at 6 Å resolution. By the comparison with similar asynchronous flight muscle thick filament structures from Lethocerus (Diptera) and Lethocerus (Hemiptera), all three present highly consistent backbone structure with very similar tail structure and have closely similar helical parameters. The myosin heads in Bombus are disordered like those of Drosophila; both insects have higher wingbeat frequencies than Lethocerus where the myosin heads are ordered. The three filament structures differ mostly in their non-myosin proteins and make the interpretation of densities corresponding to flightin and myofilin uncertain. However, using Alphafold model prediction, multiple sequence alignment and mass spectrometry, a more complete profile of flightin and myofilin has been determined. The full length of that portion of flightin within the thick filament annulus of Bombus threads its way through two myosin curved layers, contacts three other myosin curved layers and has a close contact with the Skip 3 region. The previously-identified, highly-conserved WYR domain of Bombus flightin contacts three myosin tails. With assistance from Alphafold, an atomic model was built for Bombus flightin from residue 41 to residue 151 (C-terminus). The other non-myosin protein, myofilin is more diverse in sequence, length and shape among the three reconstructed filaments, although it also shows a highly conserved density and sequence at its N-terminus, which we have named the “LKG domain”. Both flightin and myofilin have close contact with the paramyosin core, these three non-myosin proteins are believed to work together to determine and stabilize the thick filament structure. Supported by NIH/NIGMS.

Cryo-EM structure of tarantula myosin filament: Implications for analysis of myopathy mutations.

The high-resolution structure of myosin thick filaments of invertebrates has aided understanding of key muscle functions and analysis of disease mutations in humans. We previously published a low-resolution tarantula skeletal thick filament cryo-EM structure (Woodhead et al., 2005), which was used to map hypertrophic and dilated cardiomyopathy mutations (Alamo et al., 2017, Nag et al., 2017), present mostly in the head-head and head-tail interaction sites of the interacting-heads motif (IHM). This study suggested that the myosin coiled-coil tails in the filament backbone were arranged in groups of three, forming 40-Å-diameter subfilaments (Wray, 1979), but it lacked the detail required to resolve individual tails and to map the 40% of myopathy mutations that occur in the tail region of the molecule. Here we report a 5.5 Å resolution cryo-EM map of the tarantula thick filament backbone that resolves the densities of the full length of the myosin tails and their packing interactions. The map reveals that the tails do not form subfilaments but are arranged individually in layers forming a “molecular crystal,” in which the myosin coiled-coils gradually move towards the center of the filament, near the paramyosin core, while slowly curving around the filament axis. A similar arrangement was found in insect flight muscle thick filaments (Hu et al., 2016), suggesting it could be a general packing scheme in thick filaments, as originally proposed by Squire (1973). The positions of skip residues predict longer pitch regions and bending of the coiled-coils, as seen in the cryo-EM density. The structure also suggests new interactions of the blocked-head converter region with the backbone of the filament, implying hyperstability of IHMs. Improved resolution, and solution of the vertebrate thick filament structure, should enable precise mapping of tail mutations.

Glu-rich N-terminal variable region of troponin T functions as a myofilament Ca2+-reservoir to reduce SR Ca2+-cycling.

The long Glu-rich N-terminal segment of avian pectoral muscle troponin T (TnT) and C-terminal extension of insect TnT are multi-valent Ca2+-binding sites with physiologically relevant affinities. Genetic deletion of the Glu-rich C-terminal extension of insect TnT decreases muscle and heart functions but increases the tolerance of cardiomyocytes to Ca2+ overloading, indicating decreased [Ca2+]i. In contrast, cardiomyocytes from gene-edited mice expressing modified cardiac TnT with N-terminal variable region replaced by a C-terminal segment of insect TnT (51E-cTnT) show higher shortening amplitude and contraction and relaxation velocities than that of wild type (WT) control. Isolated 51E-cTnT cardiomyocytes exhibited shorter resting sarcomeres, which can be corrected by inhibiting myosin ATPase, indicating increased resting [Ca2+]i. A similar gain-of-function model,fast skeletal muscle TnTgene-edited mice with the N-terminal variable region replaced by the N-terminal segment of adult turkey pectoral muscle TnT (Tx9-fsTnT), shows normal baseline muscle functions but slower and less rising of contractile force during caffeine-induced Ca2+ release from sarcoplasmic reticulum (SR) than that of WT control, indicating a decreased SR Ca2+ store. Consistently, 51E-cTnT mouse hearts respond to beta-adrenergic stimulation or Ca2+ agonist with higher than WT ventricular peak pressure and diastolic velocity. The data support a hypothesis that the Glu-rich segments of insect and avian flight muscle TnT function as myofilament Ca2+ reservoirs to tune muscle kinetics and reduce the amount of Ca2+ cycled during contraction and relaxation. The functional effects are prominent in heterozygotes of the genetically modified flies and mice whereas the loss-of-function in Drosophila TnT and gain-of-function in 51E-cTnT and Tx9-fsTnT mice both produced homozygote lethality, indicating sensitive dose effects of the myofilament Ca2+ reservoir for use as a potent mechanism to improve energetic efficiency of cardiac and skeletal muscles.

A new tool for producing and investigating recombinant sarcomeric actin.

Actin forms many cytostructural elements, including the backbone of striated muscle thin filaments. Our mechanistic understanding of most actin-dependent processes remains limited, partly due to difficulty with recombinant actin expression. While fully-functional actin cannot be produced in bacteria, it can be generated using baculovirus expression systems. Here, we created an additional tool for recombinant actin production, for hypothesis testing and for resolving the molecular properties and cellular effects of unique variants. Specifically, we engineered Drosophila that can express untagged actins exclusively in indirect flight muscles (IFMs). Act88F encodes sarcomeric IFM actin. Attempts to rescue IFM function (i.e. flight) in Act88F-nulls, by inserting transgenic Act88F (Act88FTG-WT) ectopically throughout the genome have failed, potentially due to ineffective cis/trans regulation of Act88FTG-WT expression. To circumvent these problems, we used CRISPR-editing and introduced an attP landing site directly into Act88F, to disrupt the endogenous gene and serve as a target for site-specific transgene insertion. attP-mediated disruption of Act88F yielded flightlessness and actin-free IFMs. Transformants expressing GFP or Act88FTG-WT, from the endogenous Act88F integration locus, demonstrated robust IFM-specific protein production and restored flight, respectively. Having established the expression system, we designed Drosophila mutants to test the roles of specific actin residues in tropomyosin/myosin-binding and nemaline myopathy pathogenesis. Both Act88FTG-R147Q and Act88F TG-F352Striggered IFM hypercontraction and impaired flight. Finally, we determined whether mammalian actin could be generated and observed high-level expression of human α-cardiac actin (ACTC1), which behaved indistinguishably from bovine ACTC1 in unregulated and regulated motility (IVM) assays. We are currently comparing IVM properties of IFM-purified vs. baculovirus/Sf12-purified ACTC1. Overall, our novel fly line permits transgenic actin expression in mature muscle fibers that are themselves amenable to structural and functional analyses, and serves as a cost-effective, perpetual source of ample protein for biophysical experimentation.

Nanobodies combined with DNA-PAINT super-resolution reveal a staggered titin nanoarchitecture in flight muscles.

Sarcomeres are the force-producing units of all striated muscles. Their nanoarchitecture critically depends on the large titin protein, which in vertebrates spans from the sarcomeric Z-disc to the M-band and hence links actin and myosin filaments stably together. This ensures sarcomeric integrity and determines the length of vertebrate sarcomeres. However, the instructive role of titins for sarcomeric architecture outside of vertebrates is not as well understood. Here, we used a series of nanobodies, the Drosophila titin nanobody toolbox, recognising specific domains of the two Drosophila titin homologs Sallimus and Projectin to determine their precise location in intact flight muscles. By combining nanobodies with DNA-PAINT super-resolution microscopy, we found that, similar to vertebrate titin, Sallimus bridges across the flight muscle I-band, whereas Projectin is located at the beginning of the A-band. Interestingly, the ends of both proteins overlap at the I-band/A-band border, revealing a staggered organisation of the two Drosophila titin homologs. This architecture may help to stably anchor Sallimus at the myosin filament and hence ensure efficient force transduction during flight.

Loss of a gluconeogenic muscle enzyme contributed to adaptive metabolic traits in hummingbirds.

Hummingbirds possess distinct metabolic adaptations to fuel their energy-demanding hovering flight, but the underlying genomic changes are largely unknown. Here, we generated a chromosome-level genome assembly of the long-tailed hermit and screened for genes that have been specifically inactivated in the ancestral hummingbird lineage. We discovered that FBP2 (fructose-bisphosphatase 2), which encodes a gluconeogenic muscle enzyme, was lost during a time period when hovering flight evolved. We show that FBP2 knockdown in an avian muscle cell line up-regulates glycolysis and enhances mitochondrial respiration, coincident with an increased mitochondria number. Furthermore, genes involved in mitochondrial respiration and organization have up-regulated expression in hummingbird flight muscle. Together, these results suggest that FBP2 loss was likely a key step in the evolution of metabolic muscle adaptations required for true hovering flight.

Effects of Flight on Reproductive Development in Long-Winged Female Crickets (Velarifictorus aspersus Walker; Orthoptera: Gryllidae) with Differences in Flight Behavior.

A trade-off between the capacity for flight and reproduction has been documented extensively in wing polymorphic female insects, thereby supporting the possible fitness gain due to flightlessness. However, most of these studies were conducted without considering the effect of flight behavior. In the present study, we assessed the flight duration by long-winged (LW) females in the cricket species Velarifictorus aspersus on different days after adult emergence and examined the effect of flight on ovarian development in LW females with different flight capacities. Our results showed that the flight capacity increased with age and peaked after 5 days. In addition, the flight capacity varied among individuals, where most LW females could only take short flights (sustained flight time < 10 min) and only a few individuals could take long flights (sustained flight time > 20 min). In LW female crickets demonstrating only short flights, repeated flying for 30 or 60 min significantly promoted reproductive development. However, in those capable of long flights, reproductive development was affected only after a flight of 60 min. The flight muscles degraded after the start of rapid reproduction in those with both short and long flights. Our results indicated that the critical flight time for switching from flight to reproduction varies among LW V. aspersus female crickets with polymorphic flight behavior.

Screening and identification of genes associated with flight muscle histolysis of the house cricket Acheta domesticus.

Introduction: Flight muscle histolysis, as an important survival strategy, is a widespread phenomenon in insects and facilitates adaptation to the external environment in various insect taxa. However, the regulatory mechanism underlying this phenomenon in Orthoptera remains unknown. Methods: In this study, the flight muscle histolysis in the house cricket Acheta domesticus was investigated by transcriptomics and RNA interference. Results: The results showed that flight muscle histolysis in A. domesticus was standard and peaked within 9days after eclosion of adult crickets, and there was no significant difference in the peak time or morphology of flight muscle histolysis between males and females. In addition, the differentially expressed genes between before and after flight muscle histolysis were studied, of which AdomFABP, AdomTroponin T and AdomActin were identified as candidate genes, and after injecting the dsRNA of these three candidates, only the downregulated expression of AdomFABP led to flight muscle histolysis in A. domesticus. Furthermore, the expression level of AdomFABP was compared between before and after flight muscle histolysis based on RT-qPCR. Disscussion: We speculated that AdomFABP might play a role in the degradation of flight muscle by inhibiting muscle development. Our findings laid a molecular foundation for understanding the flight muscle histolysis.

Allometry of the pectoral flight muscles in birds: Flight style is related to variability in the mass of the supracoracoideus muscle

AbstractAvian flight is powered by a downstroke force generated by the pectoralis (P) muscle and an upstroke force generated by the supracoracoideus (SC) muscle. Some taxa, notably penguins and hummingbirds, have very low P:SC ratios associated with larger masses of the supracoracoideus. Allometric relationships of these muscles are not reported relative to body mass and presumably the two muscles will exhibit isometry in volant birds. This study collated muscle masses for over 600 species representing 28 orders of birds and used phylogenetically controlled analysis of covariance to test for the effects of taxonomic grouping on the allometry of the flight muscles in birds. The P:SC ratio and the standardized residuals for the allometric relationships, were calculated for different orders. The pectoralis scaled isometrically with body mass but the supracoracoideus muscle exhibited a slight but significant negative allometry. Both muscles showed significant effects of taxonomic group but this effect was magnified for the supracoracoideus. Wing‐propelled divers and hovering hummingbirds had disproportionately high proportions of supracoracoideus muscles but tinamous, gamebirds and pigeons, which exhibit burst flight, also had low P:SC ratios. Many taxonomic groups had a ratio around 10:1 but values of 20:1, recorded for birds of prey and owls, were associated with relatively small masses of the supracoracoideus muscle. The P:SC ratio seems to reflect differing flight styles with the greater variability being more associated with the size of the supracoracoideus, the significance of which has not necessarily been fully appreciated in the morphology and flight action of birds.

Myoblast proliferation during flight muscle development in Manduca sexta is unaffected by reduced neural signaling

In holometabolous insects, metamorphosis involves restructuring the musculature to accommodate adult-specific anatomy and behaviors. Evidence from experiments on remodeled muscles, as well as those that develop de novo, suggests that signals from the nervous system support adult muscle development by controlling myoblast proliferation rate. However, the dorsolongitudinal flight muscles (DLMs) of Manduca sexta undergo a mixed developmental program involving larval muscle fibers, and it is not known if neurons play the same role in the formation of these muscles. To address this question, we have blocked the most promising candidate pathways for neural input and examined the DLMs for changes in proliferation. Our results show that DLM development does not depend on neural activity, Hedgehog signaling, or EGF signaling. It remains to be determined how DLM growth is controlled and why neurally mediated proliferation differs between individual muscles.

Multifaceted functions of RPS27a: An unconventional ribosomal protein.

The ribosomal protein S27a (RPS27a) is cleaved from the fusion protein ubiquitin-RPS27a (Ub-RPS27a). Generally, Ub and RPS27a are coexpressed as a fusion protein but function independently after Ub is cleaved from RPS27a by a deubiquitinating enzyme. As an RP, RPS27a assembles into ribosomes, but it also functions independently of ribosomes. RPS27a is involved in the development and poor prognosis of various cancers, such as colorectal cancer, liver cancer, chronic myeloid leukemia, and renal carcinoma, and is associated with poor prognosis. Notably, the murine double minute 2/P53 axis is a major pathway through which RPS27a regulates cancer development. Moreover, RPS27a maintains sperm motility, regulates winged aphid indirect flight muscledegeneration, and facilitates plant growth. Additionally, RPS27a is a metalloprotein and mercury (Hg) biomarker. In the present review, we described the origin, structure, and biological functions of RPS27a.

The membrane domain of respiratory complex I accumulates during muscle aging in Drosophila melanogaster

The boot-shaped respiratory complex I (CI) consists of a mitochondrial matrix and membrane domain organized into N-, Q- and P-modules. The N-module is the most distal part of the matrix domain, whereas the Q-module is situated between the N-module and the membrane domain. The proton-pumping P-module is situated in the membrane domain. We explored the effect of aging on the disintegration of CI and its constituent subcomplexes and modules in Drosophila flight muscles. We find that the fully-assembled complex remains largely intact in aged flies. And while the effect of aging on the stability of many Q- and N-module subunits in subcomplexes was stochastic, NDUFS3 was consistently down-regulated in subcomplexes with age. This was associated with an accumulation of many P-module subunits in subcomplexes. The potential significance of these studies is that genetic manipulations aimed at boosting, perhaps, a few CI subunits may suffice to restore the whole CI biosynthesis pathway during muscle aging.