Trait differentiation and adaptation of plants along elevation gradients

Studies of genetic adaptation in plant populations along elevation gradients in mountains have a long history, but there has until now been neither a synthesis of how frequently plant populations exhibit adaptation to elevation nor an evaluation of how consistent underlying trait differences across species are. We reviewed studies of adaptation along elevation gradients (i) from a meta‐analysis of phenotypic differentiation of three traits (height, biomass and phenology) from plants growing in 70 common garden experiments; (ii) by testing elevation adaptation using three fitness proxies (survival, reproductive output and biomass) from 14 reciprocal transplant experiments; (iii) by qualitatively assessing information at the molecular level, from 10 genomewide surveys and candidate gene approaches. We found that plants originating from high elevations were generally shorter and produced less biomass, but phenology did not vary consistently. We found significant evidence for elevation adaptation in terms of survival and biomass, but not for reproductive output. Variation in phenotypic and fitness responses to elevation across species was not related to life history traits or to environmental conditions. Molecular studies, which have focussed mainly on loci related to plant physiology and phenology, also provide evidence for adaptation along elevation gradients. Together, these studies indicate that genetically based trait differentiation and adaptation to elevation are widespread in plants. We conclude that a better understanding of the mechanisms underlying adaptation, not only to elevation but also to environmental change, will require more studies combining the ecological and molecular approaches.     

Out of the pot and into the fire: Explaining the vulnerability of an endangered small headwater stream fish to black‐bass Micropterus spp. invasion

Introduced predatory fishes have had consistently severe consequences for native fishes in stream environments around the world, although the drivers of these effects are often unclear. In the Swartkops River headwaters in South Africa, native Eastern Cape redfin Pseudobarbus afer were always absent from sites occupied by non‐native black basses Micropterus salmoides and Micropterus dolomieu, but generally co‐occurred with the native predators Anguilla marmorata and Anguilla mossambica. A natural experiment provided by flood‐mediated recolonization of black‐bass occupied sites by P. afer demonstrated depletion in black‐bass invaded sites. Field behavioural observations of P. afer indicated that they foraged among benthic cover during the day, but suspended in open water at night. As the nocturnal A. marmorata and A. mossambica foraged actively within structural cover at night and M. dolomieu and M. salmoides are diurnal or crepuscular predators, P .afer is thus optimized to avoid predation by native anguillid predators and not the functionally unique predatory black basses. The integration of distributional, temporal population dynamics and behavioural data suggests that the severe effects of Micropterus spp. are probably a consequence of prey naïveté and behaviour evolved to evade native predators.     

Habitat selection by wintering male and female Snowy Owls on the Canadian prairies in relation to prey abundance and a competitor,the Great Horned Owl

Birds overwintering at high latitudes may find it challenging to meet their energy budgets when thermoregulatory costs are high and food availability is low. Snowy Owls (Bubo scandiacus), like most raptors, exhibit reversed sexual size dimorphism, so , if availability of high‐quality (food‐rich) habitats is limited, we predicted that larger and dominant females would use better ‐ quality habitat than males. During the winters of 2014–2015 and 2015–2016 in Saskatchewan , where many Snowy Owls overwinter annually, we measured prey (small mammal) abundance in fields with four types of cover, including cut stalks (stubble) of canola, grain and legume crops, and pasture, and related this estimate of quality to habitat selection by males and females. Small mammal abundance varied annually , but not among the three types of crop stubble. However, prey were less abundant in pastures than in the three types of crop cover in one of three years. Biweekly surveys of owls conducted during the two winters along a 60 ‐ km transect revealed weak selection for legume fields, especially by males. The home ranges of nine females with transmitters included proportionally less canola stubble than those of eight males with transmitters. Within home ranges, males avoided canola stubble and tended to use legume fields more, whereas females used all four habitat types in proportion to availability. Fewer Snowy Owls than expected were observed at locations along the transect within 800 m of Great Horned Owls (Bubo virginianus) and their associated habitats , suggesting that Snowy Owls also avoided these potential competitors on the landscape. Our results suggest that larger females outcompete smaller male Snowy Owls for home ranges in preferred habitat with less canola stubble because stubble‐free legume fields provide easier access to prey than canola fields with numerous rigid stalks.     

The molecular basis of venom resistance in a rattlesnake‐squirrel predator‐prey system

Understanding how interspecific interactions mould the molecular basis of adaptations in coevolving species is a long‐sought goal of evolutionary biology. Venom in predators and venom resistance proteins in prey are coevolving molecular phenotypes, and while venoms are highly complex mixtures it is unclear if prey respond with equally complex resistance traits. Here, we use a novel molecular methodology based on protein affinity columns to capture and identify candidate blood serum resistance proteins (“venom interactive proteins” [VIPs]) in California Ground Squirrels (Otospermophilus beecheyi) that interact with venom proteins from their main predator, Northern Pacific Rattlesnakes (Crotalus o. oreganus). This assay showed that serum‐based resistance is both population‐ and species‐specific, with serum proteins from ground squirrels showing higher binding affinities for venom proteins of local snakes compared to allopatric individuals. Venom protein specificity assays identified numerous and diverse candidate prey resistance VIPs but also potential targets of venom in prey tissues. Many specific VIPs bind to multiple snake venom proteins and, conversely, single venom proteins bind multiple VIPs, demonstrating that a portion of the squirrel blood serum “resistome” involves broad‐based inhibition of nonself proteins and suggests that resistance involves a toxin scavenging mechanism. Analyses of rates of evolution of VIP protein homologues in related mammals show that most of these proteins evolve under purifying selection possibly due to molecular constraints that limit the evolutionary responses of prey to rapidly evolving snake venom proteins. Our method represents a general approach to identify specific proteins involved in co‐evolutionary interactions between species at the molecular level.     

CD36 initiates the secretory phenotype during the establishment of cellular senescence

Cellular senescence is a unique cell fate characterized by stable proliferative arrest and the extensive production and secretion of various inflammatory proteins, a phenomenon known as the senescence‐associated secretory phenotype (SASP). The molecular mechanisms responsible for generating a SASP in response to senescent stimuli remain largely obscure. Here, using unbiased gene expression profiling, we discover that the scavenger receptor CD36 is rapidly upregulated in multiple cell types in response to replicative, oncogenic, and chemical senescent stimuli. Moreover, ectopic CD36 expression in dividing mammalian cells is sufficient to initiate the production of a large subset of the known SASP components via activation of canonical Src–p38–NF‐κB signaling, resulting in the onset of a full senescent state. The secretome is further shown to be ligand‐dependent, as amyloid‐beta (Aβ) is sufficient to drive CD36‐dependent NF‐κB and SASP activation. Finally, loss‐of‐function experiments revealed a strict requirement for CD36 in secretory molecule production during conventional senescence reprogramming. Taken together, these results uncover the Aβ–CD36–NF‐κB signaling axis as an important regulator of the senescent cell fate via induction of the SASP.     

An observation of episodic feeding and growth of larval Leiostomus xanthurus in the northern Gulf of Mexico

Four cruises were conducted in the northern Gulf of Mexico overtwo spawning seasons of the sciaenid fish Leiostomus xanthurus.On only one occasion did unusually high densities of larvaeand their principal microzooplanktonic foods co-occur. Peakdensities of larvae and microzooplankton were observed in athin lens of cool surface water that characterized a hydrographicdiscontinuity, and all larvae contained high numbers of foodorganisms in their guts. Instantaneous exponential growth ratesestimated from measurements of otolith growth increments, indicatedaccelerated growth on the day that larvae were collected. Alaboratory experiment verified that larval L. xanthurus respondsto an increased ration with accelerated growth that is detectableon otoliths. Together these data suggest that the spatial distributionof L. xanthurus larvae and their microzooplanktonic food ispatchy and that interactions of larvae and microzooplanktonmay be episodic.     

k-Binding and Degradation of [3H]Dynorphin A (1–8) and [3H]Dynorphin A (1–9) in Suspensions of Guinea Pig Brain Membranes

Following incubation of [3H]dynorphin A (1-8) and [3H]dynorphin A (1-9) with suspensions of guinea pig brain membranes, analysis of the supernatants by HPLC has shown that both peptides are degraded at 25 degrees C and at 0 degrees C. Bestatin and captopril reduce degradation at 0 degrees C but for a similar degree of protection at 25 degrees C arginine-containing dipeptides are also required. The effects of these peptidase inhibitors on the degradation profiles indicate that [3H]dynorphin A (1-8) has three main sites of cleavage: the Tyr1-Gly2, Arg6-Arg7, and Leu5-Arg6 bonds. With [3H]dynorphin A (1-9) as substrate the Arg7-Ile8 and Ile8-Arg9 bonds are also liable to cleavage. In binding assays, in contrast to the effects of peptidase inhibitors on the degradation of unbound [3H]dynorphin A (1-8) and [3H]dynorphin A (1-9), bestatin and captopril have little effect on the binding characteristics of the tritiated dynorphin A fragments at the kappa-site at 0 degrees C. However, at 25 degrees C binding is low in the absence of peptidase inhibitors. When binding at mu- and delta-sites is prevented, the maximal binding capacities of [3H]dynorphin A (1-8), [3H]dynorphin A (1-9), and [3H](-)-bremazocine at the kappa-site are similar; [3H]dynorphin A (1-9) has 5-10 times higher affinity for the kappa-site than [3H]dynorphin A (1-8). Comparison of the effects of peptidase inhibitors on unbound dynorphin A fragments with their effects in binding assays suggests that the bound peptides are protected from the action of peptidases.     

Nonspecific cytotoxicity of spleen cells and the specific cytotoxic action of thymus-derived lymphocytes in vitro

Spleen cells removed from immunized mice specifically kill allogeneic lymphoma cells in vitro, but in the presence of specific antigen nonspecific target cell growth inhibition also occurs. Only the specific target cell killing was found to be θ-sensitive, the nonspecific cytotoxicity was caused by a population of θ-resistant, adherent, and AMS-sensitive cells. Nonspecific cytotoxic effects were caused by spleen cells from normal mice after incubation with endotoxin, and these effects were inhibited by removal of the adherent cells.     

A new species of Hyphessobrycon Durbin (Characiformes: Characidae) from the western Amazon basin in Colombia and Peru

Hyphessobrycon chiribiquete n. sp. is described from the Río Caquetá drainage in Colombia and the Río Ucayali drainage in Peru, western Amazon. The new species is diagnosed from its congeners by having the following combination of characters: a conspicuous narrow midlateral stripe, starting on the sides of the body behind the opercle near the lateral line; lateral stripe overlapped anteriorly with a vertically elongated humeral blotch; inner premaxillary teeth pentacuspid; margin of anal fin falcate in mature males.     

A dynamic model linking cell growth to intracellular metabolism and extracellular by-product accumulation

Mathematical modeling of animal cell growth and metabolism is essential for the understanding and improvement of the production of biopharmaceuticals. Models can explain the dynamic behavior of cell growth and product formation, support the identification of the most relevant parameters for process design, and significantly reduce the number of experiments to be performed for process optimization. Few dynamic models have been established that describe both extracellular and intracellular dynamics of growth and metabolism of animal cells. In this study, a model was developed, which comprises a set of 33 ordinary differential equations to describe batch cultivations of suspension AGE1.HN.AAT cells considered for the production of α1-antitrypsin. This model combines a segregated cell growth model with a structured model of intracellular metabolism. Overall, it considers the viable cell concentration, mean cell diameter, viable cell volume, concentration of extracellular substrates, and intracellular concentrations of key metabolites from the central carbon metabolism. Furthermore, the release of metabolic by-products such as lactate and ammonium was estimated directly from the intracellular reactions. Based on the same set of parameters, this model simulates well the dynamics of four independent batch cultivations. Analysis of the simulated intracellular rates revealed at least two distinct cellular physiological states. The first physiological state was characterized by a high glycolytic rate and high lactate production. Whereas the second state was characterized by efficient adenosine triphosphate production, a low glycolytic rate, and reactions of the TCA cycle running in the reverse direction from α-ketoglutarate to citrate. Finally, we show possible applications of the model for cell line engineering and media optimization with two case studies.