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bioRxiv2019

PHYSIOLOGICAL GROWTH INDICES OF MAIZE (Zea mays L.) GENOTYPES IN SYLHET

Maize (Zea mays L.) is an important food and feed crop in Bangladesh as well as in the world. But its cultivation is limited in the soils of Sylhet, Bangladesh. To study the physiological growth indices of maize genotypes an experiment was carried out at the experimental field of Sylhet Agricultural University (SAU), Bangladesh during December 2014 to May 2015. The maize genotypes as the experimental materials were ZM 0001, ZM 0002, ZM 0003, ZM 0004, ZM 0005, ZM 0006 ZM 0007 and BARI Maize 6. The experiment was laid out in a Randomized Complete Block Design (RCBD) with three replications. Seeds were sown on 26 December 2014. Proper cultural management practices were followed as and when necessary during the growing period of the crop. Data were recorded on dry matter partitioning, different growth rate parameters and dry matter production of different plant parts at 30 days interval. The results indicated significant variations in almost all of the growth indices. Dry matter accumulation continued to increase from seedling to harvesting. The highest root dry matter was found in ZM 0007 (36.03 g) whereas the highest shoot and leaf dry matter was found in BARI Maize 6 (254.6 and 45.99 g, respectively) at harvest. The highest total dry matter (TDM) was produced in BARI Maize 6 at harvest (287.5 g) and AGR and CGR value was also highest in BARI Maize 6 (5.686 g day-1 and 45.48 g m-2 day-1) but at 60-90 days after germination (DAG). The highest RGR value was in ZM 0001 at seedling stage (114.1 mg g-1 day-1). A zigzag pattern graph was observed in all genotypes for RSR, RWR and SWR at different growth stages but a declining trend from seedling to harvesting was observed for LWR. Correlation between the growth rate parameters and kernel yield showed that shoot, leaf, total dry weight, AGR, CGR, RGR and SWR had significant positive correlation with yield.

plant biology↗

bioRxiv2019

Honey bee trypanosomatid parasite dynamically changes the transcriptome during the infection of honey bee and modifies the host physiology

Although there are many honey bee pathogens/parasites, it is still not understood how they change their gene expression to adapt to the host environment or how the host simultaneously responds to pathogen/parasite infection by modifying its own gene expression. Such interactions must lead to changes in the physiological states of both host and parasite. To address this question, we studied a trypanosomatid, Lotmaria passim, which can be cultured in medium and inhabit the honey bee hindgut. We found that L. passim dynamically modifies the expression of mRNAs associated with protein translation and the electron transport chain to adapt to the anaerobic and nutritionally poor honey bee hindgut at early stages of infection, and to become dormant at late stages of infection. Meanwhile, several genes are continuously up- or down-regulated during infection, including GP63 as well as genes coding for host cell signaling pathway modulators (up-regulated), and those involved in detoxification of radical oxygen species as well as flagellar formation (down-regulated). L. passim infection only slightly increases honey bee mortality and does not affect the number of microorganisms in the gut microbiota; but it induces honey bee innate immune response. Upon infection, the host appears to be in poor nutritional status, indicated by the increase in the levels of mRNAs for take-out and facilitated trehalose transporter and the decrease of vitellogenin mRNA level. Simultaneous gene expression profiling of L. passim and honey bee during infection provided insight into how both parasite and host modify their gene expressions. This study presents one of the best models to understand host-parasite interactions at the molecular and cellular levels in honey bee.

microbiology↗

bioRxiv2019

Pancreas patch-seq links physiologic dysfunction in diabetes to single-cell transcriptomic phenotypes

Pancreatic islet cells regulate glucose homeostasis through insulin and glucagon secretion; dysfunction of these cells leads to severe diseases like diabetes. Prior single-cell transcriptome studies have shown heterogeneous gene expression in major islet cell-types; however it remains challenging to reconcile this transcriptomic heterogeneity with observed islet cell functional variation. Here we achieved electrophysiological profiling and single-cell RNA sequencing in the same islet cell (pancreas patch-seq) thereby linking transcriptomic phenotypes to physiologic properties. We collected 1,369 cells from the pancreas of donors with or without diabetes and assessed function-gene expression networks. We identified a set of genes and pathways that drive functional heterogeneity in {beta}-cells and used these to predict {beta}-cell electrophysiology. We also report specific transcriptional programs that correlate with dysfunction in type 2 diabetes (T2D) and extend this approach to cryopreserved cells from donors with type 1 diabetes (T1D), generating a valuable resource for understanding islet cell heterogeneity in health and disease. Key findingsO_LIPancreas patch-seq provides a single-cell survey of function-transcriptome pairing in 1,369 islet cells from donors with and without diabetes C_LIO_LIExpression of a specific subset of genes predicts {beta}-cell electrophysiology in transcriptome-function networks. C_LIO_LICompromised {beta}-cell function in T2D correlates with altered ETV1 expression and inflammatory pathways C_LIO_LIFunctional heterogeneity in -cells maps to ER stress and islet lineage markers C_LIO_LIApplication of patch-seq to cells from rare cryopreserved islets from donors with T1D C_LI

genomics↗

bioRxiv2019

A novel human enteroid-anaerobe co-culture system to study microbial-host interaction under physiological hypoxia

Mechanistic investigations of host-microbe interactions in the human gut are limited by current co-culture model systems. The intestinal epithelium requires oxygen for viability, while gut bacteria are facultative or obligate anaerobes. The ability to model host-commensal interactions under dynamic oxygen conditions is critical to understanding host-pathogen interactions in the human gut. Here, we demonstrate a simple, cost-effective method for co-culturing obligate anaerobic bacteria with human intestinal enteroid monolayers under variable oxygen conditions. The Enteroid-Anaerobe Co-Culture (EACC) system is able to recapitulate the steep oxygen gradient seen in vivo and induce expression of hypoxia-associated phenotypes such as increased barrier integrity and expression of antimicrobial peptide genes. Using clinical strains of the commensal anaerobes Bacteroides thetaiotaomicron and Blautia sp. on established patient-derived intestinal enteroid cell lines under physiological hypoxia, the EACC system can sustain host-anaerobe interactions for at least 24 hours. Following co-culture with anaerobic bacteria, we demonstrate patient-specific differences in epithelial response, reinforcing the potential to develop a personalized medicine approach to bacteriotherapy and host-microbe interaction investigations. Our innovative EACC system provides a robust model for investigating host-microbe interactions in complex, patient-derived intestinal tissues, that facilitates study of mechanisms underlying the role of the microbiome in health and disease.

bioengineering↗

bioRxiv2019

Coronary atherosclerosis: Un-altered physiology

BackgroundEnd-stage coronary artery atherosclerosis has been studied extensively but the exact mechanisms of initiation and progression have not been defined fully. The aim of this study was to mathematically describe luminal change in relation to coronary vessel wall thickness in its progression from normal to atherosclerotic to establish whether these explain the pathophysiology.\n\nMethodsOne hundred coronary artery sections were graded histologically as normal to highly atherosclerotic. Random systemic sampling by image analysis yielded 32 measurements (lumen radius and intima, medial, and adventitial thickness) from each section along 32 evenly spaced radii.\n\nResultsThe raw data follow an undulating course in relation to successive segments in all sections analyzed, pointing to a dynamic and well-ordered system. The calculated values, studied in triplets, followed a non-synchronized parabolic course, which was converted to linearity by taking the change in numbers (n-(n-1)={Delta}) into account. The course and sign of {Delta}vessel wall (resulting from summed {Delta}intima, {Delta}media, {Delta}adventitia) and {Delta}lumen radius values were unique for each triplet. Triplets order according to {Delta}lumen radius minus {Delta}vessel wall and its course given by the trendline a-value presented stages in which increased {Delta}vessel wall resulted in increased {Delta}lumen radius in stages 1 and 3 and decreased {Delta}lumen radius in stage 2. This phenomenon was found in all sections regardless of histological indication and independent of vessel wall constituent parts (intima, media, adventitia).\n\nConclusionsSimilar basic processes are defined in all sections regardless of histological rating, indicating un-altered physiology. As such, coronary atherosclerosis can only be defined by a large to small shift of the triplets {Delta}vessel wall trendline a-value. Consequently, no parameter of vessel wall pathology exists in absolute terms. Vessel wall composition has no importance for {Delta}lumen radius.

pathology↗

bioRxiv2019

Tendon response to matrix unloading is determined by the patho-physiological niche

Aberrant matrix turnover with elevated matrix proteolysis is a hallmark of tendon pathology. While tendon disease mechanisms remain obscure, mechanical cues are central regulators. Unloading of tendon explants in standard culture conditions provokes rapid cell-mediated tissue breakdown. Here we show that biological response to tissue unloading depends on the mimicked physiological context. Our experiments reveal that explanted tendon tissues remain functionally stable in a simulated avascular niche of low temperature and oxygen, regardless of the presence of serum. This hyperthermic and hyperoxic niche-dependent catabolic switch was shown by whole transcriptome analysis (RNA-seq) to be a strong pathological driver of an immune-modulatory phenotype, with a stress response to reactive oxygen species (ROS) and associated activation of catabolic extracellular matrix proteolysis that involved lysosomal activation and transcription of a range of proteolytic enzymes. Secretomic and degradomic analysis through terminal amine isotopic labeling of substrates (TAILS) confirmed that proteolytic activity in unloaded tissues was strongly niche dependent. Through targeted pharmacological inhibition we isolated ROS mediated oxidative stress as a major checkpoint for matrix proteolysis. We conclude from these data that the tendon stromal compartment responds to traumatic mechanical unloading in a manner that is highly dependent on the extrinsic niche, with oxidative stress response gating the proteolytic breakdown of the functional collagen backbone.

molecular biology↗

bioRxiv2019

Bacteriophage can promote the emergence of physiologically sub-optimal host phenotypes

Reproduction of bacteria-specific viruses, or bacteriophage, requires the replication and translation machinery of the host cell. As a consequence, phage fitness depends intimately on the physiological state, i.e. growth rate, of the host. We include this dependence of critical phage traits on host growth rate in a mathematical model of a bacteria-phage interaction. This leads to a feedback loop between phage success, host population size, nutrient availability and host growth rate. We find that this feedback allows slow growing bacteria to have a competitive advantage in the presence of phage. Under certain conditions a slow growing host mutant can even drive the phage to extinction. Since in a phage-free environment slow growth is deleterious, the mutant subsequentely dies out as well, constituting a kind of altruistic scenario similar to abortive infections.

ecology↗

bioRxiv2019

Genomic and physiological analyses reveal that extremely thermophilic Caldicellulosiruptor changbaiensis deploys unique cellulose attachment mechanisms

The genus Caldicellulosiruptor are extremely thermophilic, heterotrophic anaerobes that degrade plant biomass using modular, multifunctional enzymes. Prior pangenome analyses determined that this genus is genetically diverse, with the current pangenome remaining open, meaning that new genes are expected with each additional genome sequence added. Given the high biodiversity observed among the genus Caldicellulosiruptor, we have sequenced and added a 14th species, Caldicellulosiruptor changbaiensis, to the pangenome. The pangenome now includes 3,791 ortholog clusters, 120 of which are unique to C. changbaiensis and may be involved in plant biomass degradation. Comparisons between C. changbaiensis and Caldicellulosiruptor bescii on the basis of growth kinetics, cellulose solubilization and cell attachment to polysaccharides highlighted physiological differences between the two species which are supported by their respective gene inventories. Most significantly, these comparisons indicated that C. changbaiensis possesses unique cellulose attachment mechanisms not observed among the other strongly cellulolytic members of the genus Caldicellulosiruptor.

microbiology↗

bioRxiv2019

Deleting a UBE3A substrate rescues impaired hippocampal physiology and learning in Angelman syndrome mice

In humans, loss-of-function mutations in the UBE3A gene lead to the neurodevelopmental disorder Angelman syndrome (AS). AS patients have severe impairments in speech, learning and memory, and motor coordination, for which there is currently no treatment. In addition, UBE3A is duplicated in >1-2% of patients with autism spectrum disorders - a further indication of the significant role it plays in brain development. Altered expression of UBE3A, an E3 ubiquitin ligase, is hypothesized to lead to impaired levels of its target proteins, but identifying the contribution of individual UBE3A targets to UBE3A-dependent deficits remains of critical importance. Ephexin5 is a putative UBE3A substrate that has restricted expression early in development, regulates synapse formation during hippocampal development, and is abnormally elevated in AS mice, modeled by maternally-derived Ube3a gene deletion. Here, we report that Ephexin5 is a direct substrate of UBE3A ubiquitin ligase activity. Furthermore, removing Ephexin5 from AS mice specifically rescued hippocampus-dependent behaviors, CA1 physiology, and deficits in dendritic spine number. Our findings identify Ephexin5 as a key driver of hippocampal dysfunction and related behavioral deficits in AS mouse models. These results demonstrate the exciting potential of targeting Ephexin5, and possibly other UBE3A substrates, to improve symptoms of AS and other UBE3A-related developmental disorders.

neuroscience↗

bioRxiv2019

Structural basis for ligand-induced inactivation of protein tyrosine receptor type Z (PTPRZ): Physiological relevance of head-to-toe RPTP dimerization

Protein tyrosine phosphatase receptor type Z (PTPRZ) has two receptor isoforms (PTPRZ-A and -B) containing tandem PTP-D1 and -D2 domains intracellularly, with only D1 being active. Pleiotrophin (PTN) binding to the extracellular region of PTPRZ leads to the inactivation of PTPase, thereby inducing oligodendrocyte precursor cell (OPC) differentiation and myelination in the CNS. However, the mechanisms responsible for the ligand-induced inactivation of PTPRZ remain unclear. We herein revealed that the crystal structure of the intracellular region of PTPRZ (PTPRZ-ICR) showed the \"head-to-toe\"-type dimer conformation, with D2 masking the catalytic site of D1. Mass spectrometry (MS) revealed that PTPRZ-ICR proteins remained in monomer-dimer equilibrium in aqueous solution, and a substrate-derived inhibitory peptide or competitive inhibitor (SCB4380) specifically bound to the monomer form in a 1:1 stoichiometric ratio, supporting the \"head-to-toe dimerization\" model for inactivation. A D2 deletion ({Delta}D2) or dimer interface mutation (DDKK) disrupted dimer formation, while the binding of SCB4380 was maintained. Similar to wild-type PTPRZ-B, monomer-biased PTPRZ-B-{Delta}D2 and PTPRZ-B-DDKK mutants efficiently dephosphorylated p190RhoGAP at Tyr-1105 when co-expressed in BHK-21 cells. The catalytic activities of these mutants were not suppressed by a treatment with PTN, but were inhibited by the cell-permeable PTPase inhibitor NAZ2329. The PTN treatment did not enhance OPC differentiation in primary cultured glial cells prepared from {Delta}D2 or catalytically-inactive CS mutant knock-in mice. Our results indicate that PTN-induced PTPRZ inactivation is attained by dimer formation of the intracellular tandem PTP domains in the head-to-toe configuration, which is physiologically relevant to the control of OPC differentiation in vivo.

biochemistry↗

bioRxiv2019

Genetic and physiological mechanisms of freezing tolerance in locally adapted populations of a winter annual

Premise of the studyDespite myriad examples of local adaptation, the phenotypes and genetic variants underlying such adaptive differentiation are seldom known. Recent work on freezing tolerance and local adaptation in ecotypes of Arabidopsis thaliana from Sweden and Italy provides the essential foundation for uncovering the genotype-phenotype-fitness map for an adaptive response to a key environmental stress.\n\nMethodsHere we examine the consequences of a naturally occurring loss of function (LOF) mutation in an Italian allele of the gene that encodes the transcription factor CBF2, which underlies a major freezing tolerance locus. We used four lines with a Swedish genetic background, each containing a LOF CBF2 allele. Two lines had introgression segments containing of the Italian CBF2 allele, and two were created using CRISPR-Cas9. We used a growth chamber experiment to quantify freezing tolerance and gene expression both before and after cold acclimation.\n\nKey resultsFreezing tolerance was greater in the Swedish (72%) compared to the Italian (11%) ecotype, and all four experimental CBF2 LOF lines had reduced freezing tolerance compared to the Swedish ecotype. Differential expression analyses identified ten genes for which all CBF2 LOF lines and the IT ecotype showed similar patterns of reduced cold responsive expression compared to the SW ecotype.\n\nConclusionsWe identified ten genes that are at least partially regulated by CBF2 that may contribute to the differences in cold acclimated freezing tolerance between the Italian and Swedish ecotypes. These results provide novel insight into the molecular and physiological mechanisms connecting a naturally occurring sequence polymorphism to an adaptive response to freezing conditions.

evolutionary biology↗

bioRxiv2019

Elizabethkingia anophelis response to iron stress: physiologic, genomic, and transcriptomic analyses

Elizabethkingia anophelis bacteria encounter fluxes of iron in the midgut of mosquitoes, where they live as symbionts. They also establish bacteremia with severe clinical manifestations in humans, and live in water service lines in hospitals. In this study, we investigated the global gene expression responses of E. anophelis to iron fluxes in the midgut of female Anopheles stephensi mosquitoes fed sucrose or blood, and in iron-poor or iron-rich culture conditions. Of 3,686 transcripts revealed by RNAseq technology, 218 were upregulated while 112 were down-regulated under iron-poor conditions. Most of these differentially expressed genes (DEGs) were enriched in functional groups assigned within \"biological process,\" \"cell component\" and \"molecular function\" categories. E. anophelis possessed 4 iron/heme acquisition systems. Hemolysin gene expression was significantly repressed when cells were grown under iron-rich or high temperature (37{degrees}C) conditions. Furthermore, hemolysin gene expression was down-regulated after a blood meal, indicating that E. anophelis cells responded to excess iron and its associated physiological stress by limiting iron loading. By contrast, genes encoding respiratory chain proteins were up-regulated under iron-rich conditions, allowing these iron-containing proteins to chelate intracellular free iron. In vivo studies showed that growth of E. anophelis cells increased 3-fold in blood-fed mosquitoes over those in sucrose-fed ones. Deletion of aerobactin synthesis genes led to impaired cell growth in both iron-rich and iron-poor media. Mutants showed more susceptibility to H2O2 toxicity and less biofilm formation than did wild-type cells. Mosquitoes with E. anophelis experimentally colonized in their guts produced more eggs than did those treated with erythromycin or left unmanipulated, as controls. Results reveal that E. anophelis bacteria respond to varying iron concentration in the mosquito gut, harvest iron while fending off iron-associated stress, contribute to lysis of red blood cells, and positively influence mosquito host fecundity.

microbiology↗

bioRxiv2019

A molecular logic of sensory coding revealed by optical tagging of physiologically-defined neuronal types

Neural circuit analysis relies on having molecular markers for specific cell types. However, for a cell type identified only by its circuit function, the process of identifying markers remains laborious. Here, we report physiological optical tagging sequencing (PhOTseq), a technique for tagging and expression-profiling cells based on their functional properties. We demonstrate that PhOTseq is capable of selecting rare cell types and enriching them by nearly one hundred-fold. We applied PhOTseq to the challenge of mapping receptor-ligand pairings among vomeronasal pheromone-sensing neurons in mice. Together with in vivo ectopic expression of vomeronasal chemoreceptors, PhOTseq identified the complete combinatorial receptor code for a specific set of ligands, and revealed that the primary sequence of a chemoreceptor was an unexpectedly strong predictor of functional similarity.

neuroscience↗

bioRxiv2019

Plasma Membrane Calcium Atpase downregulation in dopaminergic neurons alters cellular physiology and behavior in Drosophila melanogaster

Accumulation of calcium is proposed to account for selective dopaminergic neuron (DN) dysfunctionality, a characteristic of Parkinsons Disease (PD). To test the in vivo impact of calcium increment in DN physiology we downregulated the Plasma Membrane Calcium ATPase (PMCA), a bomb that extrudes cytosolic calcium, in those neurons in Drosophila melanogaster. Using th-GAL4>PMCARNAi, PMCA was selectively reduced, leading to increased cytosolic calcium and mitochondrial oxidative stress with no neurodegeneration. In the eye, PMCARNAi expression provoked a subtle disorganization, suggesting scarce toxicity. Interestingly, we observed several locomotor alterations and a higher level of dopamine in brains. Finally, flies presented a reduction of lifespan and a perimortem non-motor phenotype characterized by abdominal swelling, possibly due to constipation. We conclude that elevated cytosolic calcium in DN could trigger cellular dysfunction generating mitochondrial oxidative stress and motor and non-motor symptoms, typical of PD.

neuroscience↗

bioRxiv2019

High-throughput living-cell protein crosslinking analysis uncovers the physiological relevance of forming the \"inserted\" state of the ATP synthase ϵ-subunit

ATP synthase, a highly conserved multi-subunit enzyme complex having a common stoichiometry of 3{beta}3{gamma}{delta}{varepsilon}ab2c8-15, functions to supply ATP as the universal energy currency for cells. It comprises of the peripheral F1 sector (3{beta}3{gamma}{delta}{varepsilon}) and the membrane-integrated Fo sector (ab2c8-15). In vitro structural analyses revealed that the C-terminal domain of the {varepsilon}-subunit could adopt either an \"inserted\" or \"non-inserted\" state (with or without interacting with the /{beta}-subunits), with the former being viewed as inhibitory for the ATP hydrolysis activity of ATP synthase. Nevertheless, as common in current protein researches, the physiological relevance of such an \"inserted\" state for ATP synthase functioning is hardly known. To decipher this, designed an unnatural amino acid-mediated living-cell protein photocrosslinking analysis pipeline by developing the scarless genome-targeted site-directed mutagenesis and the high-throughput gel polyacrylamide gel electrophoresis (HT-PAGE) techniques. Employing this powerful approach, we systematically examined the interactions involving the C-terminal helix of the {varepsilon}-subunit in cells living under a variety of experimental conditions. These studies enabled us to uncover that the \"inserted\" and \"non-inserted\" states of the {varepsilon}-subunit exist as an equilibrium in cells cultured under common experimental conditions, shifting to the former upon the appearance of unfavorable conditions, acting as a low-gear state to strengthen the ATP synthesis function. Such a fine-tuning mechanism allows the ATP synthase to reversibly and instantly switch between two functional states. Further, the two powerful techniques that we developed here might be applied to many aspects of protein researches.

biochemistry↗

bioRxiv2019

Physiology-forward identification of bile acid sensitive vomeronasal receptors

Abstract/SummaryThe mouse accessory olfactory system (AOS) supports social and reproductive behavior through the sensation of environmental chemosignals. A growing number of excreted steroids have been shown to be potent AOS cues, including bile acids (BAs) found in feces. As is still the case with most AOS ligands, the specific receptors used by vomeronasal sensory neurons (VSNs) to detect BAs remain unknown. To identify VSN BA receptors, we first performed a deep analysis of VSN BA tuning using volumetric GCaMP6f/s Ca2+ imaging. These experiments revealed both broadly and narrowly tuned populations of BA-receptive VSNs with sub-micromolar sensitivities. We then developed a new physiology-forward approach for identifying AOS ligand-receptor interactions, which we call Fluorescence Live Imaging for Cell Capture and RNA-seq, or FLICCR-seq. FLICCR-seq analysis revealed 5 specific V1R-family receptors enriched in BA-sensitive VSNs. These studies introduce a powerful new approach for ligand-receptor matching and reveal biological mechanisms underlying mammalian BA chemosensation.

neuroscience↗

bioRxiv2019

Multi-trait random regression models increase genomic prediction accuracy for a temporal physiological trait derived from high-throughput phenotyping

Random regression models (RRM) are used extensively for genomic inference and prediction of time-valued traits in animal breeding, but only recently have been used in plant systems. High-throughput phenotyping (HTP) platforms provide a powerful means to collect high-dimensional phenotypes throughout the growing season for large populations. However, to date, selection of an appropriate statistical genomic framework to integrate multiple temporal traits for genomic prediction in plants remains unexplored. Here, we demonstrate the utility of a multi-trait RRM (MT-RRM) for genomic prediction of daily water usage (WU) in rice (Oryza sativa) through joint modeling with shoot biomass (projected shoot area, PSA). Three hundred and fifty-seven accessions were phenotyped daily for WU and PSA over 20 days using a greenhouse-based HTP platform. MT-RRMs that modeled additive genetic and permanent environmental effects for both traits using quadratic Legendre polynomials were used to assess genomic correlations between traits and genomic prediction for WU. Predictive abilities of the MT-RRMs were assessed using two cross-validation (CV) scenarios. The first scenario was designed to predict genetic values for WU at all time points for a set of accessions with unobserved WU. The second scenario was designed to forecast future genetic values for WU for a panel of known accessions with records for WU at earlier time periods. In each scenario we evaluated two MT-RRMs in which PSA records were absent or available for time points in the testing population. Moderate to strong genomic correlations between WU and PSA were observed across the days of imaging (0.29-0.87). In both CV scenarios, MT-RRMs showed better predictive abilities compared to single-trait RRM, and prediction accuracies were greatly improved when PSA records were available for the testing population. In summary, these frameworks provide an effective approach to predict temporal physiological traits that are difficult or expensive to quantify in large populations.

genetics↗

bioRxiv2019

Reptile-like physiology in Early Jurassic stem-mammals

There is uncertainty regarding the timing and fossil species in which mammalian endothermy arose, with few studies of stem-mammals on key aspects of endothermy such as basal or maximum metabolic rates, or placing them in the context of living vertebrate metabolic ranges. Synchrotron X-ray imaging of incremental tooth cementum shows two Early Jurassic stem-mammals, Morganucodon and Kuehneotherium, had lifespans (a basal metabolic rate proxy) considerably longer than comparably sized living mammals, but similar to reptiles, and that Morganucodon had femoral blood flow rates (a maximum metabolic rate proxy) intermediate between living mammals and reptiles. This shows maximum metabolic rates increased evolutionarily before basal rates, and that contrary to previous suggestions of a Triassic origin, Early Jurassic stem-mammals lacked the endothermic metabolism of living mammals.One Sentence Summary Surprisingly long lifespans and low femoral blood flow suggest reptile-like physiology in key Early Jurassic stem-mammals.View Full Text

paleontology↗