Mitochondria are most known for their role in energy production, but they are also implicated in many other cellular functions (apoptosis, ROS production, cell proliferation, aging). In humans, the mitochondrial DNA was believed to encode only 37 genes involved in energy production and mitochondrial translation. However, recent studies have shown that within these genes could hide several small alternative genes (genes with translation initiation or termination sequences distinct from the reference gene sequences in which they are found) coding for micropeptides with a broad spectrum of functions that can be newly added to the large list of functions in which mitochondria are involved.

Following the discovery of the mitochondrial alternative gene mtaltnd4, we try to elucidate the functions of the gene and its peptide (MTALTND4) by studying: (1) the expression pattern of the peptide in different human tissues and blood plasma, (2) the involvement of the gene in the major mitochondrial functions by exposing cells to various treatments, (3) the interaction partners of MTALTND4 by mass spectrometry and (4) the impact of the peptide on cell transcriptome. 

We have found that mtaltnd4 may potentially produce a signaling protein in response to stress that would regulate certain cell metabolic processes and there is surely more to discover.











The alternative gene mtaltnd4: uncovering the mitochondria’s hidden functions

Sea lamprey (Petromyzon marinus) invaded the Laurentian Great Lakes in the early 20th century and remain a threat to fisheries in the largest freshwater ecosystem of the world. Nowadays, population growth is restrained by a highly successful control program that mainly relies on the application of the lampricide 3-trifluoromethyl-4’-nitrophenol (TFM) to streams infested with larval sea lamprey. Recent work shows that the effectiveness of TFM is affected by temperature, with the toxicity to larval sea lamprey decreasing with increasing temperature. As such, we set out to unveil the thermal breadth of larval sea lamprey using intermittent-flow respirometry. To do so, we calculated thermal performance curves for this life stage using two approaches: First, we acclimated larvae to 7, 13, 18, 21, 25 and 28°C and tested their aerobic scope at the respective acclimation temperature. Second, we acclimated larvae to 6, 13 and 21°C and subsequently performed acute exposure tests (6, 10, 13, 15, 18, 21, 25, 28 and 31°C), with a temperature increase/decrease rate of approx. 0.1°C/min. Our results show a wide thermal tolerance, consistent with the plasticity required to become a successful invasive species. Further, sea lamprey larvae show a thermal optimum nearing 28°C, indicating that their tolerance to TFM will likely continue to increase as water temperatures in the Great Lakes continue to rise due to climate change.

Effects of temperature acclimation on thermal performance for sea lamprey larvae

Bipeds provide a unique study system to address hindlimb allometry both across and within archosaurs and mammals — having size ranges spanning five orders of magnitude yet overlapping near 1 kg body mass for most major clades. Previous work on non-avian and avian theropods shows that hindlimb proportions cluster within 1/9th of available morphospace, centered around a 60:40 tibia:femur isoline. Here we expand on previous work by including bipedal hopping mammals and examining potential drivers of divergence. We investigate 1) within group scaling, 2) phylogenetic signal, and 3) differences between hopping and striding bipeds. Our avian analysis includes 374 species, spanning 74 families and 17 orders. Our mammalian analysis is restricted to habitual bipedal hoppers and includes 47 species distributed across 5 families and 2 orders. Prior to phylogenetic correction, significant hindlimb positive allometry is seen in Anseriformes, Gruiformes, and Palaeognathae, while significant allometry of some individual segments is found in nearly all avian clades. For mammals, significant positive allometry is seen in Macropodiformes but not Rodentia. After phylogenetic correction using PGLS, significant positive allometry persists in the metatarsal segment of Galliformes, Gruiformes, Palaeognathae, and Diprotodontia. (Macropodiformes exhibited positive allometry of the hindlimb, tibia, and metatarsals after PGLS.) Examining segment proportions revealed negative allometry of the femur with respect to total hindlimb length in these same groups. Hence, whether striding or hopping — avian or mammalian, significant positive allometry of the distal segment is a hallmark of both birds and mammals.

Variable scaling of limb segment proportions in bipeds: Does allometry drive divergence?

Scorpion venoms contain different types of proteins, peptides, and molecules that can be used against predators or to immobilize prey. Toxins of venom are used for pharmaceutical purposes that require maintaining scorpions in captivity as long as possible for venom extraction purposes.
In this survey, four scorpion species from four genera; Androctonus, Buthus, Hottentotta, and Scorpio, were put in environments that vary in three variables: Diet, Temperature, Humidity. And it Was conducted to discover the influence of the captivity conditions on the venom quantity. During this research, we aim to explore these interactions, to optimize captivity conditions for more venom secretion efficiency. 
In the Light of this study, the results are very promising. This proves the huge impact of the environment on the scorpions. It could be the main key to studying other species or other venomous animals.











Performance of scorpion venom secretion in response to different captive conditions: diet, temperature and humidity on different genera of scorpions

Early-life conditions are important in shaping variation in individual quality and rates of ageing. Our understanding of this relationship between early-life conditions and late-life outcomes is particularly lacking in the context of age-related functional declines, which are often overlooked in favour of age-specific mortality and reproduction. Flight is a metabolically costly trait in insects and is closely associated with fitness in wild burying beetle populations, including Nicrophorus vespilloides. Therefore, flight represents an interesting avenue along which to examine ageing in an expensive functional trait that is closely related to fitness. We manipulated early-life environments through adjusting food availability to explore the role early-life-environments play in shaping lifespan and ageing in flight. Preliminary results find that individuals from higher quality early-life environments (abundance of food) exhibited superior peak flight-speed that was maintained across all assayed ages (10-99 days old). Peak flight speed was seen to decline only in the oldest-aged beetles (90+ days old), an age-range which exceeds that of most studies of ageing performed on this species . However, poorer-quality early-life environments (dearth of food) was associated with increased survival in later life. Beetles displayed a decreased propensity to fly at increasing ages, but no accompanying decrease in time spent in flight was detected . We show that high-quality early-life environments can contribute to improved measures of peak flight performance but have a less pronounced role in shaping patterns of age-related declines in flight. Furthermore, these early-life benefits may also be associated with reduced adult lifespan.

Effects of early-life conditions on age-related flight performance in Nicrophorus vespilloides 

Sessile benthic species are submitted to fluctuating oxygen and temperature conditions that can negatively affect their energy and redox balance. Single effects of temperature and oxygen fluctuations have been extensively studied, but their combined effects are not yet well understood. We studied the bioenergetics and oxidative stress markers in the Pacific oyster Crassostrea gigas exposed for 10 days to daily immersion-emersion cycles under the control (15°C) (H), elevated (30°C) (HW), and fluctuating (15°C in water and 30°C in air) (HF) temperature. Oysters maintained under normoxia and 15°C were used as controls. Mortality increased in the oysters exposed to hypoxia and elevated temperature indicating acute thermal stress. Oysters co-exposed to fluctuating oxygen and temperature showed a decrease in the mitochondrial aerobic capacity but no onset of anaerobiosis shown by the lack of succinate accumulation. Glycogen content decreased in the digestive gland, whereas protein content increased in the gill of the HF group indicating higher protein deposition combined with higher energy demand during reoxygenation. In contrast, the HW group showed decreased protein levels reflecting heat-induced suppression of protein synthesis. Lipid peroxidation levels were elevated in the gills of the oysters from HW (but not H or HF group) indicating that antioxidant systems of oysters can cope with hypoxia-induced oxidative stress under the normal or fluctuating temperature but not during constant warming. Thus, long-term warming combined with intermittent hypoxia can lead to breakdown of physiological functions and higher summer mortality like already observed in the German Wadden Sea.

Effects of fluctuating oxygen and temperature regime on bioenergetics and oxidative stress of the pacific oyster Crassostrea gigas

The enlarged brains of homeotherms bring behavioural advantages, but also incur high energy expenditures. The ‘expensive brain’ (EB) hypothesis posits that the energetic costs of the enlarged brain and the resulting increased cognitive abilities (CA) were met by either increased energy turnover or reduced allocation to other expensive organs, such as the gut. We tested the EB hypothesis by analysing correlated responses to selection in an experimental evolution model system, which comprises line types of laboratory mice selected for high or low basal metabolic rate (BMR), maximum (VO2max) metabolic rates and random-bred (unselected) lines. The traits are implicated in the evolution of homeothermy, having been pre-requisites for the encephalization and exceptional CA of mammals, including humans. High-BMR mice had bigger guts, but not brains, than mice of other line types. Yet, they were superior in the cognitive tasks carried out in both reward and avoidance learning contexts and had higher neuronal plasticity (indexed as the long-term potentiation) than their counterparts. Our data indicate that the evolutionary increase of CA in mammals was initially associated with increased BMR and brain plasticity. It was also fuelled by an enlarged gut, which was not traded off for brain size.

Brain size, gut size and cognitive abilities: the energy trade-offs tested in artificial selection experiment

During flight, insects can make subtle changes to their wing kinematics that in turn have large effects on their aerodynamic forces. To understand and model the above, therefore requires measurements of natural flight with appropriate spatiotemporal resolution and duration. These factors are determined by wingbeat frequency, size, and behaviour, which are limited by trade-offs within the operating equipment. Here, we describe a new and flexible arena setup that uses ten high-speed cameras to record insects flying freely in an optically clear chamber that can scale from the smallest to some of the largest insects. Pulsed far-red LEDs are focused and aligned with the high-speed cameras to provide bright, uniform backgrounds that eliminate motion blur and are beyond the insects’ visible spectrum. Separate, stereo cameras function as triggers, using real-time image analysis when subjects enter the recording volume. These triggers can control additional stimuli, such as a white light, to induce flight manoeuvres at specific times. The resultant footage is coupled with a comprehensive voxel-carving software package to automatically calculate wing and body kinematics. This includes wing deformations in the form of wing torsion, which is important for accurate aerodynamic modelling. To date, we have documented  free-flight in several species, including Calliphora vicina and Drosophila melanogaster at 6,400 fps, and Anopheles gambiae at 12,000 fps. This setup will generate a large database of high-precision insect free-flight kinematics to better our understanding of this diverse class and be used to feed into studies of insect flight control and aerodynamics.

High-precision insect wing and body kinematics acquisition using a new and flexible free-flight arena

Two rounds of genome duplication (GD) in the ancestor of vertebrates, followed by additional GD during the evolution of ray-finned fishes (Actinopterygii), expanded certain gene families, including those encoding the hypoxia inducible transcription factor (HIF). The present study analyzed Actinopterygian genomes for duplicates of HIFα, the subunit that confers oxygen-dependent gene regulation. In contrast to tetrapod vertebrates that retain three HIFα genes from the ancestral vertebrate GD, four HIFα forms were found in the genomes of primitive Actinopterygians (spotted gar and Asian arowana). All four forms have been retained in zebrafish and related species (Otocephala) and salmonids and their sister taxa (northern pike) but one of them (HIF4α) was lost during the evolution of more derived fishes (Neoteleostei). In addition, the current analyses confirm that Otocephala retain duplicates of HIF1α and HIF2α from the teleost-specific GD, provide new evidence of salmonid-specific duplicates of HIF1α, HIF2α, and HIF3α, and reveal a broad distribution of a truncated form of HIF2α in salmonids and Neoteleostei. This study delivers a comprehensive view of HIFα evolution in the ray-finned fishes, highlights the need for a consistent nomenclature, and suggests avenues for future research on this critical transcription factor.

Genomic Analysis of Hypoxia Inducible Factor Alpha Reveals Missing Ohnologs and Evidence of Widespread Positive Selection in Ray-Finned Fishes

The relationship between temperature and wingbeat frequency has been the focus of many studies over several decades and it has been shown repeatedly, across taxa, that warmer temperatures lead to higher flapping frequencies. This phenomenon is thought to be driven chiefly by the muscle properties of the flight motor. There are knock-on consequences for the kinematic pattern of the wing stroke that is required in order to generate aerodynamic forces sufficient to balance body weight. Specifically, we might predict that as frequency increases, the stroke amplitude or angle of attack must decrease to avoid producing excess force. 
Since mosquitoes have very high baseline wingbeat frequencies for their size, they operate with low wing stroke amplitudes, resulting in unusual aerodynamic mechanisms that place a greater burden of lift generation on the supinatory and pronatory rotations during the wingbeat cycle. Temperature-modulated increases in frequency reduce the stroke amplitude still further. Here, we investigate the aerodynamics of male Anopheles gambiae mosquitoes during flights recorded over a range of temperatures spanning almost 10 degrees Celsius. The kinematics were captured in a new multi-camera arena, and the flow fields were subsequently simulated by solving the incompressible Navier-Stokes equations. We present noteworthy variation in Anopheles kinematics with temperature and the mechanism of aerodynamic force production across the range of recorded kinematics.

The effect of temperature on mosquito aerodynamics

Ocean acidification and warming caused by increased anthropogenic carbon dioxide emissions poses a tremendous challenge to marine calcifiers such as intertidal bivalves. The approach to studying acclimation potential or adaptation to climate change are often conducted under artificial conditions where food is provided ad libitum and do not consider tidal emersion. These limitations present problems for extrapolating results to natural ecosystems. For instance, food provisioning and regular emersion can enhance or limit acclimation capacities of marine organisms. Here we investigate the physiological response of young Pacific oyster Crassostrea gigas exposed for 3 months to ambient and future (+3°C, -0.3 pH unit) climate scenarios under two food regimes (ad libitum vs restricted) and two tidal levels (subtidal vs intertidal, emersion twice daily) under laboratory conditions. Oysters were sampled for biometric and physiological rate measurements (respiration and food intake), biochemistry (energetic reserves and enzyme assay) and histology to evaluate their reproductive status. At the end of the experiment, oysters were further challenged with a viral disease to investigate the physiological cost of acclimation to these conditions and their immune response. Preliminary analyses suggest that food level was the most influential factor, followed by climate scenario and tidal level. We indeed found that growth, food intake, reproduction and disease resistance of oysters were negatively affected by food restriction. Future conditions enhanced oyster physiological rates and sexual maturation, particularly at high food levels. Finally, tidal level had no major effect on these variables, suggesting physiological compensatory mechanisms during emersion. Our study suggests that the oyster is robust to future climatic conditions, even when feeding was restricted. A detailed analysis of the results will be presented at the conference.

Physiological and immune response of oysters to climate change as a function of diet and tidal regime

Analogous to the situation in several lepidopteran and dipteran insects also the larval stages of some echinoderms and hemichordates (ambulacraria superphylum) evolved highly alkaline midguts up to pH 10.5. Despite its pivotal role in species´ sensitivity to changes in seawater pH, the underlying epithelial transport mechanisms are largely unknown. Using ion-selective microelectrodes we found that pluteus larva of the purple sea urchin not only have highly alkaline midgut fluids (pH ~9) but also a substantial reduced sodium concentration (150 mM) compared to the surrounding sea water (450 mM). We pharmacologically investigated the role of Na+/H+ exchangers in intracellular pH (pHi) regulation and midgut proton and sodium maintenance using the NHE inhibitor 5 (n ethyl n isopropyl)amiloride (EIPA). While life cell imaging demonstrated the importance of NHEs in pHi regulation of midgut epithelia cells, basolateral EIPA application decreased midgut pH whereas luminal application, via micro-injections, increased midgut [Na+], without affecting pH. Gene expression analyses identified putative NHE candidates for midgut pH and Na+ homeostasis. Based on this information an antibody was generated against the sea urchin Slc9a2, which showed that the protein is localized in luminal membranes of the midgut. Additionally the use of specific vivo morpholino knock down of spslc9a2 provoked an increase in midgut [Na+] without affecting pH underlining the role of this transporter in midgut Na+ maintenance. 
This work provides new insights of NHEs being involved in ion regulatory mechanisms, especially the maintenance of pH and [Na+] in larval midgut fluids and thereby show conserved features to insect and vertebrate digestive systems, which may contribute to the ability of sea urchin larvae to cope with changes in seawater pH.






Underline digital video library

The alternative gene mtaltnd4: uncovering the mitochondria’s hidden functions

Effects of temperature acclimation on thermal performance for sea lamprey larvae

Variable scaling of limb segment proportions in bipeds: Does allometry drive divergence?

Performance of scorpion venom secretion in response to different captive conditions: diet, temperature and humidity on different genera of scorpions

Effects of early-life conditions on age-related flight performance in Nicrophorus vespilloides

Effects of fluctuating oxygen and temperature regime on bioenergetics and oxidative stress of the pacific oyster Crassostrea gigas

Brain size, gut size and cognitive abilities: the energy trade-offs tested in artificial selection experiment

High-precision insect wing and body kinematics acquisition using a new and flexible free-flight arena

Genomic Analysis of Hypoxia Inducible Factor Alpha Reveals Missing Ohnologs and Evidence of Widespread Positive Selection in Ray-Finned Fishes

The effect of temperature on mosquito aerodynamics

Physiological and immune response of oysters to climate change as a function of diet and tidal regime

Midgut Na+ and pH homeostasis is differentally regulated by Na+/H+ exchangers in the sea urchin larva

Stay up to date with the latest Underline news!

PRESENTATIONS

CONFERENCES

COMPANY

RESOURCES