Physiological costs of warning: Defensive hissing increases metabolic rate and evaporative water loss in a venomous snake.

To minimize predation risk and the cost of confronting predators, prey have developed a range of defensive strategies and warning signals. Although advantageous, defensive warnings may also induce physiological and energy costs to the emitter. Ventilatory sounds (hissing) are the most distributed warning sound in vertebrates. Because they involve the respiratory apparatus, defensive hissing may substantially increase evaporative water loss. Herein, we examined the determinants of hissing as well as its physiological costs in a medium-sized venomous snake, the long-nosed viper (Vipera ammodytes). We first used a neutral arena and applied standardized stimulation to measure the occurrence and acoustic characteristics of warning hissing. Then, we used open-flow respirometry to quantify changes in respiratory gas exchanges (oxygen consumption and evaporative water loss) during defensive responses. We demonstrated that males are more likely to engage in sound warnings when stimulated. Expirations generated the strongest signals compared to inspiration but did not differ between sexes. We found that defensive hissing dramatically increased average metabolic rate and evaporative water loss during the 10-minute stimulation period, and this effect was more pronounced in males. Metabolic rates and evaporative water loss were closely related to the duration of hissing. Overall, our results indicate that respiratory-based warning sounds induce significant physiological costs and may alter water balance. The higher responsiveness in males than females likely reflects sexually selective pressure (higher mobility for mate acquisition) and enhanced risk exposure.

Biological constraint, evolutionary spandrels and antagonistic pleiotropy.

Maximum lifespan differs greatly between species, indicating that the process of senescence is largely genetically determined. Senescence evolves in part due to antagonistic pleiotropy (AP), where selection favors gene variants that increase fitness earlier in life but promote pathology later. Identifying the biological mechanisms by which AP causes senescence is key to understanding the endogenous causes of aging and its attendant diseases. Here we argue that the frequent occurrence of AP as a property of genes reflects the presence of constraint in the biological systems that they specify. This arises particularly because the functionally interconnected nature of biological systems constrains the simultaneous optimization of coupled traits (interconnection constraints), or because individual traits cannot evolve (impossibility constraints). We present an account of aging that integrates AP and biological constraint with recent programmatic aging concepts, including costly programs, quasi-programs, hyperfunction and hypofunction. We argue that AP mechanisms of costly programs and triggered quasi-programs are consequences of constraint, in which costs resulting from hyperfunction or hypofunction cause senescent pathology. Impossibility constraint can also cause hypofunction independently of AP. We also describe how AP corresponds to Stephen Jay Gould's constraint-based concept of evolutionary spandrels, and argue that pathologies arising from AP are bad spandrels. Biological constraint is a conceptual missing link between ultimate and proximate causes of senescence, including diseases of aging.

Non-senescent species are not immortal: Stress and decline in two planaria species.

Potential immortality is observed in several species (e.g. prickly pear cactus, hydra and flatworms) and is indicative of their negligible or even negative senescence rates. Unlike in senescent species, which experience reduced individual performance with age due to physiological degradation, species with negligible or negative senescence display mortality rates that remain constant or decline with age, respectively. These rates vary across taxa and are correlated with life history traits. Yet, the extent to which variable resource availability, a key driver of variation in life history traits, impacts species that show negligible or negative senescence is currently unknown. Here, we examine whether and how variation in the quantity, quality and feeding interval of resources impact population structure, population performance and life history trait trade-offs in two long-lived planaria that do not senesce: Schmidtea mediterranea and Dugesia tahitiensis. In a full factorial design, different combinations of resource quantity (reduced intake, standard intake and high intake) and quality (high and low quality) were provided in two different feeding intervals (7-day and 14-day intervals) for 19 weeks. We show that variability in resource availability, via decreases in quantity, quality and frequency of resources, does not diminish population viability in either species but does result in suboptimal conditions of stress in S. mediterranea. The high population viability we report can be attributed to two different mechanisms: increased reproduction or increased investment into maintenance at the expense of reproduction. Moreover, which mechanism was responsible for said high population viability was context-dependent and modulated by the specific life history strategy of the two planaria species. We show that suboptimal conditions can cause stress responses that have significant impacts on non-senescent species. The context-dependent response we observe suggests that species that do not senesce but are subject to suboptimal conditions of stress may ultimately exhibit declines in performance and ultimately die. A clearer understanding of the impact of suboptimal conditions of resource availability on non-senescent species is needed to determine the extent of stress experienced and ultimately whether a species can truly be immortal.

The effects of pressure on anticipatory postural adjustments during a jump shot in basketball.

BACKGROUND: Anticipatory postural adjustments (APAs) play an important role in feedforward control of dynamic movements, such as jump shot performance in basketball. It is known that jump shot performance declines under pressure from a defender (shot blocker). RESEARCH QUESTION: Does pressure from a shot blocker affect the APAs of a jump shot in basketball? Is jump shot performance in basketball associated with APAs? METHODS: Fourteen healthy male university basketball players performed jump shots under pressure and non-pressure (free) conditions by a shot blocker. Using a force plate, the APAs were defined as occurring until the point of thrust (TH) phase, and ground reaction force (GRF) and center of pressure (COP) at that moment were assessed. To assess jump shot performance, the maximum GRF during the TH phase (THmax), jumping height, and success score of the shot (accuracy score: AS) were measured by using the vertical component of the force plate. Two-way ANOVA examined the effects of the phase and condition on APA duration. The effects of pressure from a shot blocker on each variable (subjective pressure intensity, AS, GRF, and COP) were analyzed using a pairwise t-test or Wilcoxon signed-rank tests. Relationships between changes in jump shot performance and GRF or COP variables were assessed via Spearman's correlation analysis. Differences between the pressure and free conditions were denoted by p/f (pressure/free). RESULTS: The APA duration was shorter under the pressure condition compared to the free condition. The THmax and jump height values were greater under the pressure condition relative to the free condition. Across conditions, changes in COP sway velocity of the APA phase were significantly and negatively correlated with AS. SIGNIFICANCE: The results of this study suggest that pressure from a shot blocker shortens APA duration and decreases jump shot performance.

A Bayesian pharmacokinetics integrated phase I-II design to optimize dose-schedule regimes.

The schedule of administering a drug has profound impact on the toxicity and efficacy profiles of the drug through changing its pharmacokinetics (PK). PK is an innate and indispensable component of the dose-schedule optimization. Motivated by this, we propose a Bayesian PK integrated dose-schedule finding (PKIDS) design to identify the optimal dose-schedule regime by integrating PK, toxicity, and efficacy data. Based on the causal pathway that dose and schedule affect PK, which in turn affects efficacy and toxicity, we jointly model the three endpoints by first specifying a Bayesian hierarchical model for the marginal distribution of the longitudinal dose-concentration process. Conditional on the drug concentration in plasma, we jointly model toxicity and efficacy as a function of the concentration. We quantify the risk-benefit of regimes using utility-continuously updating the estimates of PK, toxicity, and efficacy based on interim data-and make adaptive decisions to assign new patients to appropriate dose-schedule regimes via adaptive randomization. The simulation study shows that the PKIDS design has desirable operating characteristics.

Fine Root Traits across Different Root Orders and Their Associations with Leaf Traits in 15 Co-Occurring Plant Species from the Desert-Oasis Transition Zone in the Hexi Corridor, Gansu Province, China.

Fine root traits embody trade-offs between resource acquisition and conservation in plants. Yet, the differentiation of these traits across root orders, the existence of a root economics spectrum (RES) spanning these orders, and their linkage with leaf traits remain underexplored. In this study, we analyzed the first three root orders and leaf traits of 15 co-occurring plant species, including ten herbs and five shrubs, from the desert-oasis transition zone of the Hexi Corridor. We measured twelve morphological and chemical traits to investigate the relationships between root and leaf traits. Our results revealed significant variation in root traits both among species and within species across different root orders. We identified RES that spanned root orders, with higher-order roots exhibiting more conservative traits and lower-order roots displaying traits aligned with resource acquisition. Additionally, leaf and fine root traits showed partially decoupled adaptive strategies, yet evidence also supported the existence of a leaf economics spectrum (LES) and a potentially two-dimensional whole plant economics spectrum (WPES). Our findings suggest synergistic resource allocation strategies between fine roots and the entire plant, emphasizing the importance of root order in understanding fine root structure, function, and their interactions with other plant organs. These insights advance the understanding of fine root traits and their integration within the broader plant economics spectrum. Nevertheless, the differences in fine root traits across root orders, the presence of a root economics spectrum (RES) spanning these orders, and the relationships between fine root and leaf traits remain underexplored. We examined the first three root orders and leaves of 15 co-occurring plant species (ten herbs and five shrubs) from the desert-oasis transition zone in the Hexi Corridor, measured twelve key morphological and chemical traits. We observed substantial variation in root traits among species and root orders within species. The root economics spectrum (RES) spanned across root orders, with higher-order roots positioned at the conservative end and lower-order roots at the acquisitive end of the "investment-return" strategy axis. Leaf and fine root traits of the 15 co-occurring plant species exhibited partially decoupled adaptive strategies. However, there was also evidence for the presence of a leaf economics spectrum (LES) and a whole plant economics spectrum (WPES), with the WPES potentially being two-dimensional. Furthermore, our findings suggest synergistic resource strategies between fine roots and the whole plant. Concurrently, the significant interspecific and intraspecific differences in fine root traits, combined with the presence of a root economics spectrum across root orders, underscore the critical importance of root order in studying fine root structure, function, and their associations with other plant organs. Our findings offer valuable insights for future research on fine root traits, the RES, and their integration with the whole plant economics spectrum.

Hepatic transcriptomic analysis reveals differential regulation of metabolic and immune pathways in three strains of chickens with distinct growth rates exposed to mixed parasite infections.

During parasite infections, the liver may prioritise immune-related pathways over its metabolic functions. Intestinal infections caused by Ascaridia galli and Heterakis gallinarum impair feed intake, nutrient absorption, and weight gain. Histomonas meleagridis, vectored by H. gallinarum, can also damage liver tissues, potentially impairing liver functions. This study examined the hepatic gene expression in three strains of chickens: Ross-308 (R), Lohmann Brown Plus (LB), and Lohmann Dual (LD), 2 weeks after an experimental infection (n = 18) with both A. galli and H. gallinarum or kept as uninfected control (n = 12). Furthermore, H. gallinarum infection led to a co-infection with H. meleagridis. The mixed infections reduced feed intake and the average daily weight gain (P < 0.001). The infections also increased the plasma concentrations of alpha (1)-acid glycoprotein and the antibody titre against H. meleagridis (P = 0.049), with no strain differences (P > 0.05). For host molecular response, 1887 genes were differentially expressed in LD, while 275 and 25 genes were differentially expressed in R and LB, respectively. The up-regulated genes in R and LD were mostly related to inflammatory and adaptive immune responses, while down-regulated genes in LD were involved in metabolic pathways, including gluconeogenesis. Despite performance differences among the strains, worm burdens were similar, but hepatic molecular responses differed significantly. Moreover, there was an indication of a shift in hepatic functions towards immune-related pathways. We, therefore, conclude that the liver shifts its functions from metabolic to immune-related activities in chickens when challenged with mixed parasite species.

Phosphorus availability influences disease-suppressive soil microbiome through plant-microbe interactions.

BACKGROUND: Soil nutrient status and soil-borne diseases are pivotal factors impacting modern intensive agricultural production. The interplay among plants, soil microbiome, and nutrient regimes in agroecosystems is essential for developing effective disease management. However, the influence of nutrient availability on soil-borne disease suppression and associated plant-microbe interactions remains to be fully explored. T his study aims to elucidate the mechanistic understanding of nutrient impacts on disease suppression, using phosphorous as a target nutrient. RESULTS: A 6-year field trial involving monocropping of tomatoes with varied fertilizer manipulations demonstrated that phosphorus availability is a key factor driving the control of bacterial wilt disease caused by Ralstonia solanacearum. Subsequent greenhouse experiments were then conducted to delve into the underlying mechanisms of this phenomenon by varying phosphorus availability for tomatoes challenged with the pathogen. Results showed that the alleviation of phosphorus stress promoted the disease-suppressive capacity of the rhizosphere microbiome, but not that of the bulk soil microbiome. This appears to be an extension of the plant trade-off between investment in disease defense mechanisms versus phosphorus acquisition. Adequate phosphorus levels were associated with elevated secretion of root metabolites such as L-tryptophan, methoxyindoleacetic acid, O-phosphorylethanolamine, or mangiferin, increasing the relative density of microbial biocontrol populations such as Chryseobacterium in the rhizosphere. On the other hand, phosphorus deficiency triggered an alternate defense strategy, via root metabolites like blumenol A or quercetin to form symbiosis with arbuscular mycorrhizal fungi, which facilitated phosphorus acquisition as well. CONCLUSION: Overall, our study shows how phosphorus availability can influence the disease suppression capability of the soil microbiome through plant-microbial interactions. These findings highlight the importance of optimizing nutrient regimes to enhance disease suppression, facilitating targeted crop management and boosting agricultural productivity. Video Abstract.

[Spatio-temporal Evolution and Trade-off/Synergy Analysis of Ecosystem Services in Regions of Rapid Urbanization： A Case Study of the Lower Yellow River Region].

As the forefront of implementing China's "Yellow River Major National Strategy," the lower Yellow River area has caused irreversible "constructive destruction" to the regional natural ecosystem and ecological functions while accelerating the process of urbanization and has become an area of sharp contradiction between ecological protection and high-quality development of the river basin. Therefore, based on ArcGIS and MATLAB software, this study used the InVEST and RUSLE models to quantitatively assess water yield, habitat quality, and soil conservation services of the lower Yellow River Region from 1990 to 2020 and analyzed the spatial and temporal characteristics and their interaction relationships of various ecosystem services. The results showed that： ① In the period from 1990 to 2020, the land urbanization process accelerated significantly, with the expansion of construction land increasing by 39.89%, whereas the area of other major land types had declined to varying degrees. ② From 1990 to 2020, the distribution patterns on the county scale and grid-scale in the lower Yellow River Region were relatively consistent. The water yield and soil conservation experienced a changing trend of first decreasing and then increasing, and the spatial distribution pattern of water yield gradually shifted to more in the east and less in the west. The spatial distribution patterns of soil conservation and habitat quality remained unchanged throughout the period, with the high values distributed in the hilly or mountainous regions of the higher terrain and the low values mainly in the plains of the gentle terrain. ③ At both the grid scale and county scale, the interaction relationships between various ecosystem services had been dominated by synergy and showed significant spatial heterogeneity. Especially at the county level, strong trade-offs were occurring in a few counties. For example, the relationship between water yields and habitat quality was a significant and strong trade-off between Weishan County and Huaiyin District. The study quantified the spatial and temporal evolution characteristics of ecosystem services in the lower Yellow River Region and clarified the trade-off synergistic relationships between ecosystem services, which can provide a scientific basis for ecological protection and watershed management under the rapid urbanization process.

Rapid growth and the evolution of complete metamorphosis in insects.

More than 50% of all animal species are insects that undergo complete metamorphosis. The key innovation of these holometabolous insects is a pupal stage between the larva and adult when most structures are completely rebuilt. Why this extreme lifestyle evolved is unclear. Here, we test the hypothesis that a trade-off between growth and differentiation explains the evolution of this novelty. Using a comparative approach, we find that holometabolous insects grow much faster than hemimetabolous insects. Using a theoretical model, we then show how holometaboly evolves under a growth-differentiation trade-off and identify conditions under which such temporal decoupling of growth and differentiation is favored. Our work supports the notion that the holometabolous life history evolved to remove developmental constraints on fast growth, primarily under high mortality.

Independent Control Over the H/OH Adsorption: Breaking the Trade-Off Between H/OH-Adsorption and H2O-Dissociation of Platinum-Group Metal Electrocatalyst for Hydrogen Evolution Reaction.

Platinum-group metals catalysts (such as Rh, Pd, Ir, Pt) have been the most efficient hydrogen evolution reaction (HER) electrocatalysts due to their moderate H adsorption strength, while the high H2O-dissociation barrier in alkaline media restrains the catalytic performance of PGM catalysts. However, the optimization of the H2O-dissociation barrier and *H/*OH binding energy toward their individual optima is limited due to the constraints of their scaling relationship on a single active site. Here, a coordinatively unsaturated "M─Ox─W" (M = Rh, Pd, Ir, Pt) active area is constructed, where H and OH species are anchored on Pt-group metal sites and inactive W sites for individual regulation. By combining experiments and density functional theory calculations, the introduction of extra OH-adsorption sites (coordinatively unsaturated WO3-x) avoids the competitive adsorption of H and OH on the single site, while the enhanced OH-adsorption capacity on the coordinatively unsaturated WO3-x effectively facilitates the adsorption/dissociation of interfacial H2O. As a result, the representative Rh-WO3-x catalyst exhibits outstanding catalytic activity and durability for HER. The findings of this work not only provide valuable insights for the design of efficient PGM catalysts for HER but also shed light on the development of electrocatalysts for other catalytic reactions.

Corrigendum: The trade-off of Vibrio parahaemolyticus between bacteriophage resistance and growth competitiveness.

[This corrects the article DOI: 10.3389/fmicb.2024.1346251.].

Detecting context dependence in the expression of life history trade-offs.

Life history trade-offs are one of the central tenets of evolutionary demography. Trade-offs, depicting negative covariances between individuals' life history traits, can arise from genetic constraints, or from a finite amount of resources that each individual has to allocate in a zero-sum game between somatic and reproductive functions. While theory predicts that trade-offs are ubiquitous, empirical studies have often failed to detect such negative covariances in wild populations. One way to improve the detection of trade-offs is by accounting for the environmental context, as trade-off expression may depend on environmental conditions. However, current methodologies usually search for fixed covariances between traits, thereby ignoring their context dependence. Here, we present a hierarchical multivariate 'covariance reaction norm' model, adapted from Martin (2023), to help detect context dependence in the expression of life-history trade-offs using demographic data. The method allows continuous variation in the phenotypic correlation between traits. We validate the model on simulated data for both intraindividual and intergenerational trade-offs. We then apply it to empirical datasets of yellow-bellied marmots (Marmota flaviventer) and Soay sheep (Ovis aries) as a proof-of-concept showing that new insights can be gained by applying our methodology, such as detecting trade-offs only in specific environments. We discuss its potential for application to many of the existing long-term demographic datasets and how it could improve our understanding of trade-off expression in particular, and life history theory in general.

Contextual control demands determine whether stability and flexibility trade off against each other.

Cognitive stability, the ability to focus on a current task, and cognitive flexibility, the ability to switch between different tasks, are traditionally conceptualized as opposing end-points on a one-dimensional continuum. This assumption obligates a stability-flexibility trade-off - greater stability equates to less flexibility, and vice versa. In contrast, a recent cued task-switching study suggested that stability and flexibility can be regulated independently, evoking a two-dimensional perspective where trade-offs are optional (Geddert & Egner, Journal of Experimental Psychology: General, 151, 3009-3027, 2022). This raises the question of under what circumstances trade-offs occur. We here tested the hypothesis that trade-offs are guided by cost-of-control considerations whereby stability and flexibility trade off in contexts that selectively promote stability or flexibility, but not when neither or both are promoted. This proposal was probed by analyzing whether a trial-level metric of a stability-flexibility trade-off, an interaction between task-rule congruency and task sequence, varied as a function of a broader block-level context that independently varied demands on stability or flexibility by manipulating the proportion of incongruent and switch trials, respectively. In Experiment 1, we reanalyzed data from Geddert and Egner, Journal of Experimental Psychology: General, 151, 3009-3027, (2022); Experiment 2 was a conceptual replication with a design tweak that controlled for potential confounds due to local trial history effects. The experiments produced robust evidence for independent stability and flexibility adaptation, and for a context-dependent expression of trial-level stability-flexibility trade-offs that generally conformed to the cost-of-control predictions. The current study thus documents that stability-flexibility trade-offs are not obligatory but arise in contexts where either stability or flexibility are selectively encouraged.

Ecological management zone of Taiyuan City based on the supply and demand of ecosystem services.

Clarifying the matching degree and the trade-offs and synergies between supply and demand of ecosystem services is of significance for scientific division of management zoning and sustainable urban development. We calculated the supply and demand of ecosystem services at the sub-district (town) scale of Taiyuan based on multi-source data, explored the coldspots and hotspots area of the supply-demand ratio and the trade-offs and synergies of six ecosystem services using the Getis-Ord Gi* tool and correlation analysis, and proposed strategies based on the regional characteristics of natural-resource and socio-economy. Results showed the distribution of the supply and demand of ecosystem services had a spatial heterogeneity. In terms of supply, the area with high supply of carbon storage, air purification, thermal environment regulation and recreation service were located in the east and west parts, that of soil conservation in the west and water yield in the south part. In terms of demand, the demand distribution of carbon storage, thermal environment regulation, water yield and recreation service were characterized by high in the central and east-south area, and low in the periphery, and high demand of air purification in south and north parts, soil conservation in west part. There were substantial mismatches between the demand and supply of ecosystem services. The risk levels of the supply and demand of six ecosystem services showed a decreasing pattern from the Fenhe River to the eastern and western mountains. There were trade-offs between water yield and other five ecosystem services in their supply, while air purification and soil conservation had trade-offs with other four ecosystem services in demand. Based on the regional ecological management framework, we divided the study area into three primary zones and eight secondary zones, and proposed differentiated ecological management strategies to provide theoretical support for ecological zoning. The results could provide a basis for balancing the relationship of supply and demand of ecosystem services and promoting the sustainable development of the city.

Responses of ecosystem service trade-offs and synergies in Guangfo Metropolitan Area to multidimensional expansion of urban space.

Understanding the responses of ecosystem service trade-offs and synergies in metropolitan areas to the multidimensional expansion of urban space is of great significance for the optimization of regional land spatial pattern and high-quality development. With the Guangfo Metropolitan Area as research region, we used land use data and natural ecological environment data from 2000 to 2020 to measure the expansion characteristics of urban space in the dimensions of scale, distribution, and morphology by using the landscape pattern indices. We further calculated four main ecosystem services: urban cooling, habitat quality, recreation, and water conservation by the InVEST model, quantified the trade-off and synergistic relationship of multiple ecosystem services by the coupling coordination degree model, and explored its response to multidimensional urban spatial expansion by using the multi-scale geographically weighted regression model. The results showed that urban land use scale in the Guangfo Metropolitan Area continued to increase from 2000 to 2020, with an accelerated growth rate from 2010 to 2020. The ave-rage patch area of urban land in the central area and the urban land of small patches in the northeast increased, evolving from a "dual-center" structure to a "single-center" one. The distance between urban land patches in the Guangfo Metropolitan Area was relatively small, indicating a compact distribution of urban land. The distance between newly developed urban land patches was also small, but had gradually increased in recent years. The patch shape of urban land was relatively regular and less complex, but the complexity of the newly added urban land gra-dually increased. The ecosystem service trade-offs and synergies in the Guangfo Metropolitan Area had undergone significant changes, with a decrease in synergies and an increase in trade-off, and extreme trade-offs had gradually become dominant. The response of ecosystem services synergies to changes in urban land use scale was the most intense and had spatial heterogeneity, while the response to the change of distribution and morphological characte-ristics of urban land showed periodic differences.

Perceptuomotor skill acquisition in a solo manual ball-and-beam task with varying accuracy requirements.

In the manual ball-and-beam task, participants have to control a ball that is rolling continuously on a long and hand-held beam. Since the task can be performed individually, in a solo action setting, as well as collaboratively, in a (dyadic) joint action setting, it allows us to investigate how joint performances arise from individual performances, which we investigate in a series of interrelated studies. Here we focused on individual skill acquisition on the ball-and-beam task in the solo action setting, with the goal to characterize the behavioral dynamics that arise from learning to couple (ball motion) perception and (beam motion) action. By moving a beam extremity up and down to manipulate the beam's inclination angle, the task's objective was to roll the ball as fast as and accurately as possible between two indicated targets on the beam. Based on research into reciprocal aiming tasks, we hypothesized that the emergent dynamics of the beam's inclination angle would be constrained by the size of the targets, such that large targets would evoke a continuous beam movement strategy, while small targets would lead to a discrete beam movement strategy. 16 participants individually practiced the task in two separate six-block sessions. Each block consisted of one trial per target-size condition (small, medium and large). Overall, the number of target hits increased over trials, due to a larger range of motion of the beam's inclination angle, a stronger correlation between the ball and beam motion and a smaller variability of the beam motion. Contrary to our expectations, target size did not appreciably affect the shape of the beam movement patterns. Instead, we found stable inter-individual differences in the movement strategies adopted that were uncorrelated with the number of target hits on a trial. We concluded that multiple movement strategies may lead to success on the task, while individual skill acquisition was characterized by the refinement of behavioral dynamics that emerged in an early stage of learning. We speculate that such differences in individual strategies on the task may affect the interpersonal coordination that arises in joint-action performances on the task.

Stable isotopes reveal sex- and context-dependent amino acid routing in green anole lizards (Anolis carolinensis).

Allocation of acquired resources to phenotypic traits is affected by resource availability and current selective context. While differential investment in traits is well documented, the mechanisms driving investment at lower levels of biological organization, which are not directly related to fitness, remain poorly understood. We supplemented adult male and female Anolis carolinensis lizards with an isotopically labelled essential amino acid (13C-leucine) to track routing in four tissues (muscle, liver, gonads and spleen) under different combinations of resource availability (high- and low-calorie diets) and exercise training (sprint training and endurance capacity). We predicted sprint training should drive routing to muscle, and endurance training to liver and spleen, and that investment in gonads should be of lower priority in each of the cases of energetic stress. We found complex interactions between training regime, diet and tissue type in females, and between tissue type and training, and tissue type and diet in males, suggesting that males and females adjust their 13C-leucine routing strategies differently in response to similar environmental challenges. Importantly, our data show evidence of increased 13C-leucine routing in training contexts not to muscle as we expected, but to the spleen, which turns over blood cells, and to the liver, which supports metabolism under differing energetic scenarios. Our results reveal the context-specific nature of long-term trade-offs associated with increased chronic activity. They also illustrate the importance of considering the costs of locomotion in studies of life-history strategies.

Hook loop dynamics engineering transcended the barrier of activity-stability trade-off and boosted the thermostability of enzymes.

The improvement of enzyme thermostability often accompanies the decreased activity due to the loss of the key regions' flexibility. As a representative structure, unlocking the potential of loop dynamics will not only provide new ideas for stabilization strategies, but also help to deepen the understanding of the relationship between enzyme structural dynamics and function. In this study, a creative "hook loop dynamics engineering" (HLoD) strategy was successfully proposed for simultaneously improving the thermostability and maintaining activity of the model enzyme, Candida Antarctica lipase B. A small and smart mutant library involving five key residues located at the "hook loop" was meticulously identified and systematically investigated and thus yielded a five-point multiple mutant M1 (L147S/T244P/S250P/T256D/N292D), demonstrating a remarkable 7.0-fold increase in thermostability at 60 °C compared to the wild-type (WT). Furthermore, the activity of M1 remained comparable to that of WT, effectively transcending the barrier of activity-stability trade-off. Molecular dynamics simulations revealed that the precise regulation of hook loop dynamics via intermolecular interactions, such as salt bridges and hydrogen bonding, curbed the excessive flexibility of the pivotal regions α5 and α10 at high temperatures, thus driving the substantial enhancement of the thermostability of M1. Refining the dynamics of the flexible region via HLoD, which transcended the barrier of activity-stability trade-off, exhibited to be a robust and potentially universal strategy for designing enzymes with outstanding thermostability and activity.

Thermostability and activity improvement in l-threonine aldolase through targeted mutations in V-shaped subunit.

l-threonine aldolase (LTA) catalyzes the synthesis of ß-hydroxy-α-amino acids, which are important chiral intermediates widely used in the fields of pharmaceuticals and pesticides. However, the limited thermostability of LTA hinders its industrial application. Furthermore, the trade-off between thermostability and activity presents a challenge in the thermostability engineering of this enzyme. This study proposes a strategy to regulate the rigidity of LTA's V-shaped subunit by modifying its opening and hinge regions, distant from the active center, aiming to mitigate the trade-off. With LTA from Bacillus nealsonii as targeted enzyme, a total of 25 residues in these two regions were investigated by directed evolution. Finally, mutant G85A/M207L/A12C was obtained, showing significantly enhanced thermostability with a 20 °C increase in T5060 to 66 °C, and specific activity elevated by 34 % at the optimum temperature. Molecular dynamics simulations showed that the newly formed hydrophobicity and hydrogen bonds improved the thermostability and boosted proton transfer efficiency. This work enhances the thermostability of LTA while preventing the loss of activity. It opens new avenues for the thermostability engineering of other industrially relevant enzymes with active center located at the interface of subunits or domains.