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Search indexed bioRxiv preprints in genomics, neuroscience, cell biology and bioinformatics. Read source abstracts and check manuscript versions; preprints are not peer reviewed.

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bioRxiv2017

RNA-seq highlights parallel and contrasting patterns in the evolution of the nuclear genome of holo-mycoheterotrophic plants

* While photosynthesis is the most notable trait of plants, several lineages of plants (so-called holo-heterotrophs) have adapted to obtain organic compounds from other sources. The switch to heterotrophy leads to profound changes at the morphological, physiological and genomic levels.\n\n* Here, we characterize the transcriptomes of three species representing two lineages of mycoheterotrophic plants: orchids (Epipogium aphyllum and Epipogium roseum) and Ericaceae (Hypopitys monotropa). Comparative analysis is used to highlight the parallelism between distantly related holo-heterotrophic plants.\n\n* In both lineages, we observed genome-wide elimination of nuclear genes that encode proteins related to photosynthesis, while systems associated with protein import to plastids as well as plastid transcription and translation remain active. Genes encoding components of plastid ribosomes that have been lost from the plastid genomes have not been transferred to the nuclear genomes; instead, some of the encoded proteins have been substituted by homologs. The nuclear genes of both Epipogium species accumulated mutations twice as rapidly as their photosynthetic relatives; in contrast, no increase in the substitution rate was observed in H.monotropa.\n\n* Holo-heterotrophy leads to profound changes in nuclear gene content. The observed increase in the rate of nucleotide substitutions is lineage specific, rather than a universal phenomenon among non-photosynthetic plants.

genomics↗
bioRxiv2017

A minimal model of protein allocation during phototrophic growth

Photoautotrophic growth depends upon an optimal allocation of finite cellular resources to diverse intracellular processes. Commitment of a certain mass fraction of the proteome to a specific cellular function, typically reduces the proteome available for other cellular functions. Here, we develop a minimal semi-quantitative kinetic model of cyanobacterial phototrophic growth to describe such trade-offs of cellular protein allocation. The model is based on coarse-grained descriptions of key cellular processes, in particular carbon uptake, metabolism, photosynthesis, and protein translation. The model is parametrized using literature data and experimentally obtained growth curves. Of particular interest are the resulting cyanobacterial growth laws as fundamental characteristics of cellular growth. We show that the model gives rise to similar growth laws as observed for heterotrophic organisms, with several important differences due to the distinction between light energy and carbon uptake. We discuss recent experimental data supporting the model results and show that minimal growth models have implications for our understanding of the limits of phototrophic growth and bridge a gap between molecular physiology and ecology.

systems biology↗
bioRxiv2017

Correction of autoimmune IL2RA mutations in primary human T cells using non-viral genome targeting

Human T cells are central to physiological immune homeostasis, which protects us from pathogens without collateral autoimmune inflammation. They are also the main effectors in most current cancer immunotherapy strategies1. Several decades of work have aimed to genetically reprogram T cells for therapeutic purposes2-5, but as human T cells are resistant to most standard methods of large DNA insertion these approaches have relied on recombinant viral vectors, which do not target transgenes to specific genomic sites6, 7. In addition, the need for viral vectors has slowed down research and clinical use as their manufacturing and testing is lengthy and expensive. Genome editing brought the promise of specific and efficient insertion of large transgenes into target cells through homology-directed repair (HDR), but to date in human T cells this still requires viral transduction8, 9. Here, we developed a non-viral, CRISPR-Cas9 genome targeting system that permits the rapid and efficient insertion of individual or multiplexed large (>1 kilobase) DNA sequences at specific sites in the genomes of primary human T cells while preserving cell viability and function. We successfully tested the potential therapeutic use of this approach in two settings. First, we corrected a pathogenic IL2RA mutation in primary T cells from multiple family members with monogenic autoimmune disease and demonstrated enhanced signalling function. Second, we replaced the endogenous T cell receptor (TCR) locus with a new TCR redirecting T cells to a cancer antigen. The resulting TCR-engineered T cells specifically recognized the tumour antigen, with concomitant cytokine release and tumour cell killing. Taken together, these studies provide preclinical evidence that non-viral genome targeting will enable rapid and flexible experimental manipulation and therapeutic engineering of primary human immune cells.

genetics↗
bioRxiv2017

What the structural-functional connectome reveals about brain aging: The key role of the fronto-striatal-thalamic circuit and the rejuvenating impact of physical activity

Physiological ageing affects brain structure and function impacting its morphology, connectivity and performance. However, at which extent brain-connectivity metrics reflect the age of an individual and whether treatments or lifestyle factors such as physical activity influence the age-connectivity match is still unclear. Here, we assessed the level of physical activity and collected brain images from healthy participants (N=155) ranging from 10 to 80 years to build functional (resting-state) and structural (tractography) connectivity matrices that were combined as connectivity descriptors. Connectivity descriptors were used to compute a maximum likelihood age estimator that was optimized by minimizing the mean absolute error. The connectivity-based estimated age, i.e. the brain-connectome age (BCA), was compared to the chronological age (ChA). Our results were threefold. First, we showed that ageing widely affects the structural-functional connectivity of multiple structures, such as the anterior part of the default mode network, basal ganglia, thalamus, insula, cingulum, hippocampus, parahippocampus, occipital cortex, fusiform, precuneus and temporal pole. Second, our analysis showed that the structure-function connectivity between basal ganglia and thalamus to orbitofrontal and frontal areas make a major contribution to age estimation. Third, we found that high levels of physical activity reduce BCA as compared to ChA, and vice versa, low levels increment it. In conclusion, the BCA model results highlight the impact of physical activity and the key role played by the connectivity between basal ganglia and thalamus to frontal areas on the process of healthy aging. Notably, the same methodology can be generally applied both to evaluate the impact of other factors and therapies on brain ageing, and to identify the structural-functional brain connectivity correlate of other biomarkers than ChA.

neuroscience↗
bioRxiv2017

Patterns of gene body methylation predict coral fitness in new environments

Despite widespread taxonomic representation, the function of gene body methylation (GBM) remains uncertain. One hypothesis is that GBM mediates phenotypic plasticity. To investigate this hypothesis, we performed whole-genome methylation and transcriptome profiling on reciprocally transplanted colony fragments of the reef-building coral Acropora millepora. GBM was only slightly affected by transplantation but these small changes correlated with coral fitness in the new environment. Specifically, for transplanted corals, similarity in GBM patterns to native corals positively correlated with growth rate, as well as carbohydrate, protein, lipid and endosymbiont content. Between populations, elevated GBM positively correlated with transcription, supporting previous findings that GBM is associated with stable and active transcription. Contrary to expectations however, changes in transcription as a result of transplantation did not correlate with changes in GBM and did not predict fitness. This indicates that on physiological time scales GBM is not directly coupled to transcription, leaving open the question about the mechanism linking GBM to fitness during acclimatization.

ecology↗
bioRxiv2017

Snord116-dependent diurnal rhythm of DNA methylation in mouse cortex

Rhythmic oscillations of physiological processes depend on integrating the circadian clock and diurnal environment. DNA methylation is epigenetically responsive to daily rhythms, as a subset of CpG dinucleotides in brain exhibit diurnal rhythmic methylation. A major genetic effect on rhythmic methylation was identified in a mouse Snordll6 deletion model of the imprinted disorder Prader-Willi syndrome (PWS). Of the >23,000 diurnally rhythmic CpGs identified in wild-type cortex, 97% lost rhythmic methylation in PWS cortex. Circadian dysregulation of a second imprinted Snord cluster at the Temple/Kagami-Ogata syndrome locus was observed at the level of methylation, transcription, and chromatin, providing mechanistic evidence of crosstalk. Genes identified by diurnal epigenetic changes in PWS mice overlapped rhythmic and PWS-specific genes in human brain and were enriched for PWS-relevant obesity phenotypes and pathways. These results support the proposed evolutionary relationship between imprinting and sleep, and suggest possible chronotherapy in the treatment of PWS and related disorders.

genomics↗
bioRxiv2017

Quantitative Characterization of Biological Age and Frailty Based on Locomotor Activity Records

We performed a systematic evaluation of the relationships between locomotor activity and signatures of frailty, morbidity, and mortality risks using physical activity records from the 2003 - 2006 National Health and Nutrition Examination Survey (NHANES) and UK BioBank (UKB). We proposed a statistical description of the locomotor activity tracks and transformed the provided time series into vectors representing physiological states for each participant. The Principal Components Analysis of the transformed data revealed a winding trajectory with distinct segments corresponding to subsequent human development stages. The extended linear phase starts from 35 40 years old and is associated with the exponential increase of mortality risks according to the Gompertz mortality law. We characterized the distance traveled along the aging trajectory as a natural measure of biological age and demonstrated its significant association with frailty and hazardous lifestyles, along with the remaining lifespan and healthspan of an individual. The biological age explained most of the variance of the log-hazard ratio that was obtained by fitting directly to mortality and the incidence of chronic diseases. Our findings highlight the intimate relationship between the supervised and unsupervised signatures of the biological age and frailty, a consequence of the low intrinsic dimensionality of the aging dynamics.

systems biology↗
bioRxiv2017

Dose-response surface fits to drought and nitrogen limitation applied together allow mapping of loci that exhibit nonlinear responses

Crop improvement must accelerate to feed an increasing human population in the face of environmental changes. Breeding programs can include anticipated climatic changes and genetic architecture to optimize improvement strategies. We analyzed the genetic architecture underlying the response of Zea mays to combinations of water and nitrogen stresses. Recombinant inbreds were subjected to nine combinations of the two stresses using an optimized response surface design, and their growth was measured. Three-dimensional dose response surfaces were fit globally and to each polymorphic allele to determine which genetic markers were associated with different response surfaces. Three quantitative trait loci that produced nonlinear surfaces were mapped. Alleles that performed better in combinations of mid-range stresses were typically not the alleles that performed best under combinations of extreme stresses. To develop physiologically relevant models for future genetic analyses, we modeled the network that explains the response surfaces. The network contains two components, an elliptical paraboloid and a plane, that each combine the nitrogen and water inputs. The relative weighting of the two components and the inputs is governed by five parameters. We estimated parameter values for the smoothed surfaces from the experimental lines using a set of points that covered the most distinctive regions of the three-dimensional surfaces. Surfaces computed using these values reproduced the smoothed experimental surfaces well, especially in the neighborhood of the peaks, as judged by three different criteria. The parameters exaggerated the amplitudes of the simulated surfaces. Experiments using single stresses could misestimate responses to their combinations and disguise loci that respond nonlinearly. The three-dimensional shape evaluation strategy used here more thoroughly compares nonlinear, nonplanar responses. We encourage the application of our findings and methods to experiments that mix crop protection measures, stresses, or both, on elite and landrace germplasm.

genetics↗
bioRxiv2017

Trans-omic analysis reveals fed and fasting insulin signal across phosphoproteome, transcriptome, and metabolome

The concentration and temporal pattern of insulin selectively regulate multiple cellular functions. To understand how insulin dynamics are interpreted by cells, we constructed a trans-omic network of insulin action in FAO hepatoma cells from three networks--a phosphorylation-dependent cellular functions regulatory network using phosphoproteomic data, a transcriptional regulatory network using phosphoproteomic and transcriptomic data, and a metabolism regulatory network using phosphoproteomic and metabolomic data. With the trans-omic regulatory network, we identified selective regulatory networks that mediate differential responses to insulin. Akt and Erk, hub molecules of insulin signaling, encode information of a wide dynamic range of dose and time of insulin. Down-regulated genes and metabolites in glycolysis had high sensitivity to insulin (fasting insulin signal); up-regulated genes and dicarboxylic acids in the TCA cycle had low sensitivity (fed insulin signal). This integrated analysis enables molecular insight into how cells interpret physiologically fed and fasting insulin signals.\n\nHighlightsO_LIWe constructed a trans-omic network of insulin action using multi-omic data.\nC_LIO_LIThe trans-omic network integrates phosphorylation, transcription, and metabolism.\nC_LIO_LIWe classified signaling, transcriptome, and metabolome by sensitivity to insulin.\nC_LIO_LIWe identified fed and fasting insulin signal flow across the trans-omic network.\nC_LI

systems biology↗
bioRxiv2017

A Genome Scan for Genes Underlying Adult Body Size Differences between Central African Pygmies and their Non-Pygmy Neighbors

BackgroundCentral African hunter-gatherer Pygmy populations have reduced body size compared with their often much larger agricultural non-Pygmy neighbors, potentially reflecting adaptation to the anatomical and physiological constraints of their lifestyle in tropical rainforests. Earlier studies investigating the genetics of the pygmy phenotype have focused on standing height, one aspect of this complex phenotype that is itself a composite of skeletal components with different growth patterns. Here, we extend the investigations of standing height to the variability and genetic architecture of sitting height and subischial leg length as well as body mass index (BMI) in a sample of 406 unrelated West Central African Pygmies and non-Pygmies.\n\nResultsIn addition to their significantly reduced standing height compared with non-Pygmies, we find Pygmies to have significantly shorter sitting heights and subischial leg lengths as well as higher sitting/standing height ratios than non-Pygmies. However, while male Pygmies had significantly lower BMI compared with male non-Pygmies, the BMI of females were instead similar. Consistent with prior observations with standing height, sitting height and subischial leg length were strongly correlated with inferred levels of non-Pygmy genetic admixture while BMI was instead weakly correlated, likely reflecting the greater contribution of non-genetic factors to the determination of body weight compared with height. Using 196,725 SNPs on the Illumina Cardio-MetaboChip with genotypes on 358 Pygmy and 169 non-Pygmy individuals together with single-and multi-marker association approaches, we identified a single genomic region and seven genes associated with Pygmy/non-Pygmy categorization as well as 9, 10, 9, and 10 genes associated with standing and sitting height, sitting/standing height ratio, and subischial leg length, respectively. Many of the genes identified have putative functions consistent with a role in determining their associated trait as well as the complex Central African pygmy phenotype.\n\nConclusionsThese findings highlight the potential of modestly sized datasets of Pygmies and non-Pygmies to detect biologically meaningful associations with traits contributing to the Central African pygmy phenotype. Moreover, they provide new insights into the phenotypic and genetic bases of the complex pygmy phenotype and offer new opportunities to facilitate our understanding of its complex evolutionary origins.

genetics↗
bioRxiv2017

EPAC1 regulates endothelial Annexin A2 cell surface translocation and plasminogen activation

Annexins, a family of highly conserved calcium-and phospholipid-binding proteins, play important roles in a wide range of physiological functions. Among the twelve known annexins in human, Annexin A2 (AnxA2) is one of the most extensively studied and has been implicated in various human diseases. AnxA2 can exist as a monomer or a heterotetrameric complex with S100A10 (P11) and plays a critical role in many cellular processes including exocytosis/endocytosis and membrane organization. At the endothelial cell surface, (AnxA2*P11)2 tetramer, acting as a coreceptor for plasminogen and tissue plasminogen activator (t-PA), accelerates t-PA dependent activation of the fibrinolytic protease, plasmin, the enzyme responsible for thrombus dissolution and degradation of fibrin. This study shows that exchange proteins directly activated by cAMP isoform 1 (EPAC1) interacts with AnxA2 and regulates its biological functions by modulating its membrane translocation in endothelial cells. Using genetic and pharmacological approaches, it is demonstrated that EPAC1, acting through the PLC{varepsilon}-PKC pathway, inhibits AnxA2 surface translocation and plasminogen activation. These results suggest that EPAC1 plays a role in the regulation of fibrinolysis in endothelial cells and may represent a novel therapeutic target for disorders of fibrinolysis.

cell biology↗
bioRxiv2017

Anoctamin 9/TMEM16J is a Cation Channel Activated by cAMP/PKA Signal

Anoctamins are membrane proteins that consist of 10 homologs. ANO1 and ANO2 are anion channels activated by intracellular calcium that meditate numerous physiological functions. ANO6 is a scramblase that redistributes phospholipids across the cell membrane. However, the others are not well characterized. We found ANO9/TMEM16J is a cation channel activated by a cAMP-dependent PKA. Intracellular cAMP activated robust currents in whole-cells expressing ANO9 and inhibited by PKA blockers. A cholera toxin and purified PKA also activated ANO9. The cAMP-induced ANO9 currents were permeable to cations. The mutation of a possible phosphorylation site at Ser245 elicited a block of the cAMP-dependent activation. High levels of Ano9 transcripts were found in intestines. Human intestinal SW480 cells showed cAMP-dependent currents. We conclude that ANO9 is a cation channel activated by the cAMP/PKA pathway and could play a role in intestine function.

biophysics↗
bioRxiv2017

A SUMO-dependent feedback loop senses and controls the biogenesis of nuclear pore subunits

While the activity of multiprotein complexes is crucial for cellular metabolism, little is known about the mechanisms that collectively control the expression of their components in response to the cellular demand. Here, we have investigated the regulations targeting the biogenesis of the nuclear pore complex (NPC), the macromolecular assembly mediating nucleocytoplasmic exchanges. Systematic analysis of RNA-binding proteins interactomes, together with in vivo and in vitro assays, revealed that a subset of NPC mRNAs are specifically bound by Hek2, a yeast hnRNP K-like protein. Hek2-dependent NPC mRNAs translational repression and protein turnover are further shown to finely tune the levels of NPC subunits. Strikingly, Hek2 binding to its target mRNAs requires prior desumoylation by the NPC-associated SUMO protease Ulp1. Mutations or physiological perturbations altering NPC integrity lead to a decrease in the levels of active Ulp1 and to the accumulation of sumoylated, inactive forms of Hek2. Our results support the existence of a quality control mechanism involving Ulp1 as a sensor of NPC integrity and Hek2 as a repressor of NPC biogenesis.

molecular biology↗
bioRxiv2017

Quantitative mapping of fluorescently tagged cellular proteins using FCS-calibrated four dimensional imaging

EDITORIAL SUMMARYThis protocol describes how to estimate and spatially resolve the concentration and copy number of fluorescently tagged proteins in live cells using fluorescence imaging and fluorescence correlation spectroscopy (FCS).\n\nTWEETDetermining protein concentrations and copy numbers in live cells using fluorescence correlation spectroscopy (FCS)-calibrated imaging.\n\nCOVER TEASER Map protein concentrations with FCS-calibrated imagingUp to four primary research articles where the protocol has been used and/or developed:\n\nO_LIWalther, N., Hossain, M. J., Politi, A. Z., Koch, B., Kueblbeck, M., Oedegaard-Fougner, O., Lampe, M. and J. Ellenberg (2018). A quantitative map of human Condensins provides new insights into mitotic chromosome architecture. bioRxiv, 237834. https://doi.org/10.1101/2378342.\nC_LIO_LICai, Y., Hossain, M. J., Heriche, J.-K., Politi, A. Z., Walther, N., Koch, B., Wachsmuth, M., Nijmeijer, B., Kueblbeck, M., Martinic, M., Ladurner, R., Peters, J.M. and J. Ellenberg (2017). An experimental and computational framework to build a dynamic protein atlas of human cell division. bioRxiv, 227751 https://doi.org/10.1101/227751\nC_LIO_LIGermier, T., Kocanova, S., Walther, N., Bancaud, A., Shaban, H.A., Sellou, H., Politi, A.Z., Ellenberg, J., Gallardo, F. and K. Bystricky (2017). Real-Time Imaging of a Single Gene Reveals Transcription-Initiated Local Confinement. Biophysical Journal, 113(7), 1383-1394, https://doi.org/10.1016/j.bpj.2017.08.014.\nC_LIO_LICuylen, S., Blaukopf, C., Politi, A. Z., Muller-Reichert, T., Neumann, B., Poser, I., Ellenberg, J., Hyman, A.A., and D.W. Gerlich (2016). Ki-67 acts as a biological surfactant to disperse mitotic chromosomes. Nature, 535(7611), 308-312. http://doi.org/10.1038/nature18610.\nC_LI\n\nAbstractThe ability to tag a protein at its endogenous locus with a fluorescent protein (FP) enables the quantitative understanding of protein dynamics at the physiological level. Genome editing technology has now made this powerful approach routinely applicable to mammalian cells and many other model systems, opening up the possibility to systematically and quantitatively map the cellular proteome in four dimensions. 3D time-lapse confocal microscopy (4D imaging) is an essential tool to investigate spatial and temporal protein dynamics, however it lacks the required quantitative power to make absolute and comparable measurements required for systems analysis. Fluorescence correlation spectroscopy (FCS) on the other hand provides quantitative proteomic and biophysical parameters such as protein concentration, hydrodynamic radius and oligomerization but lacks the ability for high-throughput application in 4D spatial and temporal imaging. Here, we present an automated experimental and computational workflow that integrates both methods and delivers quantitative 4D imaging data in high-throughput. These data is processed to yield a calibration curve relating the fluorescence intensities of image voxels to absolute protein abundance. The calibration curve allows the conversion of the arbitrary fluorescence intensities to protein amounts for all voxels of 4D imaging stacks. With our workflow the users can acquire and analyze hundreds of FCS-calibrated image series to map their proteins of interest in four dimensions. Compared to other protocols, the current protocol does not require additional calibration standards and provides an automated acquisition pipeline for FCS and imaging data. The protocol can be completed in 1 day.

molecular biology↗
bioRxiv2017

Leaf shedding as a bacterial defense in Arabidopsis cauline leaves

Plants utilize an innate immune system to protect themselves from disease. While many molecular components of plant innate immunity resemble the innate immunity of animals, plants also have evolved a number of truly unique defense mechanisms, particularly at the physiological level. Plants flexible developmental program allows them the unique ability to simply produce new organs as needed, affording them the ability to replace damaged organs. Here we develop a system to study pathogen-triggered leaf abscission in Arabidopsis. Cauline leaves infected with the bacterial pathogen Pseudomonas syringae abscise as part of the defense mechanism. Pseudomonas syringae lacking a functional type III secretion system fail to elicit an abscission response, suggesting that the abscission response is a novel form of immunity triggered by effectors. HAESA/HAESA-like 2, INFLORESCENCE DEFICIENT IN ABSCISSION, and NEVERSHED are all required for pathogen-triggered abscission to occur. Additionally phytoalexin deficient 4, enhanced disease susceptibility 1, salicylic acid induction deficient 2, and senescence-associated gene 101 plants with mutations in genes necessary for bacterial defense and salicylic acid signaling, and NahG transgenic plants with low levels of salicylic acid fail to abscise cauline leaves normally. Bacteria that physically contact abscission zones trigger a strong abscission response; however, long distance signals are also sent from distal infected tissue to the abscission zone, alerting the abscission zone of looming danger. We propose a threshold model regulating cauline leaf defense where minor infections are handled by limiting bacterial growth, but when an infection is deemed out of control, cauline leaves are shed. Together with previous results our findings suggest that salicylic acid may regulate both pathogen- and drought-triggered leaf abscission.\n\nAuthor SummaryPlants have a flexible development program that determine their form. We describe an organ level defense response in Arabidopsis to bacterial attack where plants simply shed heavily infected leaves. The genetics regulating this defense mechanism are comprised of both classical defense genes and floral organ abscission genes working together. Long distance signals are transmitted from infected areas to abscission zones which activate the abscission receptor. Salicylic acid, a defense hormone, signaling is necessary for cauline leaf abscission.

genetics↗
bioRxiv2017

Out-of-Register Aβ42 Assemblies as Models for Neurotoxic Oligomers and Fibrils

We propose a variant of the recently found S-shaped A{beta}1-42-motif that is characterized by out-of-register C-terminal {beta}-strands. We show that chains with this structure can not only form fibrils that are compatible with the NMR signals, but also barrel-shaped oligomers that resemble the ones formed by the much smaller cylindrin peptides. Running at physiological temperatures long all-atom molecular dynamics simulations with an explicit solvent, we study the stability of these constructs and show that they are plausible models for neurotoxic oligomers. Analyzing the transitions between different assemblies we suggest a mechanism for amyloid formation in Alzheimers disease.

biochemistry↗
bioRxiv2017

Urinary candidate biomarkers in an experimental autoimmune myocarditis rat model

Urine is a better source than plasma for biomarker studies, as it can accumulate all changes in the body. Various candidate urinary biomarkers of physiological conditions, kidney disease and even brain dysfunction, have been detected in urine; however, urine has rarely been used to reflect cardiac diseases. As the clinical presentations of myocarditis are heterogeneous, reliable and sensitive diagnostic biomarkers of myocarditis are very important. In this study, candidate urinary biomarkers in the myosin-induced autoimmune myocarditis rat models were characterized using the isobaric tandem mass tag labeling approach coupled with high-resolution mass spectrometry. Compared with controls, forty-six urinary proteins were significantly changed in the myocarditis rats; among them, ten had previously been associated with myocarditis, twelve corresponding gene products have been annotated as mainly cardiovascular network genes by the Ingenuity Pathway Analysis, and four urinary proteins were validated by western blot.

molecular biology↗
bioRxiv2017

Natural selection on plasticity of thermal traits in a highly seasonal environment

This preprint has been reviewed and recommended by Peer Community In Evolutionary Biology (http://dx.doi.org/10.24072/pci.evolbiol.100048). For ectothermic species with broad geographical distributions, latitudinal/altitudinal variation in environmental temperatures (averages and extremes) are expected to shape the evolution of physiological tolerances and the acclimation capacity (i.e., degree of phenotypic plasticity) of natural populations. This can create geographical gradients of selection in which environments with greater thermal variability (e.g., seasonality) tend to favour individuals that maximize performance across a broader range of temperatures compared to more stable environments. Although thermal acclimation capacity plays a fundamental role in this context, it is unknown whether natural selection targets this trait in natural populations. Here we addressed such an important gap in our knowledge by measuring survival, through mark recapture integrated into an information-theoretic approach, as a function of the plasticity of critical thermal limits for activity, behavioural thermal preference and the thermal sensitivity of metabolism in the northernmost population of the four-eyed frog Pleurodema thaul. Overall, our results indicate that thermal acclimation in this population is not being targeted by directional selection, although there might be signals of selection on individual traits. According to the most supported models, survival decreased in individuals with less tolerance to cold when cold-acclimated (probably because daily low extremes are frequent during the cooler periods of the year) and increased with body size. However, in both cases, the directional selection estimates were non-significant.

evolutionary biology↗