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bioRxiv2018

Physiological and transcriptomic analysis of yellow leaf

As important deciduous tree, Populus deltoides Marsh possesses a high ornamental value for its leaves remaining yellow during the non-dormant period. However, little is known about the regulatory mechanism of leaf coloration in Populus deltoides Marsh. Thus, we analyzed physiological and transcriptional differences of yellow leaves (mutant) and green leaves (wild-type) of Populus deltoides Marsh. Physiological experiments showed that the contents of chlorophyll (Chl) and carotenoid are lower in mutant, the flavonoid content is not differed significantly between mutant and wild-type. Transcriptomic sequencing was further used to identify 153 differentially expressed genes (DEGs). Functional classifications based on Gene Ontology enrichment and Genomes enrichment analysis indicated that the DEGs were involved in Chl biosynthesis and flavonoid biosynthesis pathway. Among these, geranylgeranyl diphosphate (CHLP) genes associated with Chl biosynthesis showed down-regulation, while chlorophyllase (CLH) genes associated with Chl degradation were up-regulated in yellow leaves. The expression levels of these genes were further confirmed using quantitative real-time PCR (RT-qPCR). Furthermore, the measurement of the main precursors of Chl confirmed that CHLP is vital enzymes for the yellow leaf color phenotype. Consequently, the formation of yellow leaf color is due to disruption of Chl synthesis and catabolism rather than flavonoid content. These results contribute to our understanding of mechanisms and regulation of leaf color variation in poplar at the transcriptional level.

bioinformatics↗

bioRxiv2018

Physiological regulation of bud burst in grapevine

The physiological constraints on bud burst in woody perennials, including the prerequisite for vascular development remain unresolved. Both light and tissue oxygen status have emerged as important cues for vascular development in other systems, however, light requirement appears to be facultative in grapevine, and the information related to the spatial variability of oxygen in buds is unclear. Here, we analysed apoplastic development at early stages of grapevine bud burst and combined molecular modelling with histochemical techniques to determine the pore size of cell walls in grapevine buds. The data demonstrate that quiescent grapevine buds were impermeable to apoplastic dyes (acid fuchsin and eosin Y) until after bud burst was established. The molecular exclusion size was calculated to be 2.1 nm, which would exclude most macromolecules except simple sugars and phytohormones. In vivo experiments show that grapevine buds were able to resume growth even following excision from the cane, and that the outer scales of grapevine buds may participate in the biochemical repression of bud burst. Furthermore, we demonstrate that the tissue oxygen partial pressure data correlated well with structural heterogeneity within the bud and differences in tissue density. These data consolidate evidence that the meristematic core becomes rapidly oxygenated during bud burst. Taken together, and when put in the context of earlier studies, these data provide solid evidence that the physiological and biochemical events that initiate bud burst reside within the bud, and question the role of long distance signalling in this developmental transition.\n\nHighlightsO_LIThe apoplastic pore size between the grapevine bud and the mother vine is dynamically regulated in the transition to bud burst.\nC_LIO_LIThe molecular exclusion size of the apoplastic connection between the bud and cane is calculated 2.1 nm prior to the initiation of bud burst.\nC_LIO_LIThe structural heterogeneity of the bud explains the spatial variance in tissue oxygen status, and the meristematic core is oxygenated during the initiation of bud burst.\nC_LIO_LILong distance maternal signals are not a requirement for bud burst.\nC_LI

plant biology↗

bioRxiv2018

Unpredictable effects of the genetic background of transgenic lines in physiological quantitative traits

Most physiology, fitness and disease phenotypes are considered complex traits since they exhibit continuous variation in natural populations. The use of homozygous inbred strains allows the assessment of the impact of genetic composition on complex phenotypes. Nevertheless, to understand gene function, we often combine transgenic lines to assess the phenotype of interest in a heterozygous state. Here, using inbred wild-type Drosophila strains, we assessed the phenotypic variation of six physiology and fitness traits: female fecundity, survival and intestinal mitosis upon oral infection, defecation rate and fecal pH upon oral infection, and terminal tracheal cell branching in hypoxia. Indeed, we found continuous variation in all traits tested. To estimate the extent to which small genetic background differences affected these traits, we assessed the effects of commonly used Drosophila UAS-RNAi transgenic strains and their backcrossed isogenized counterparts in the same assays. We tested 20 non-isogenic strains (10 KK and 10 GD) from the Vienna Drosophila Resource Center and their isogenic counterparts without Gal4 induction and found that the different phenotypes were variably sensitive to the genetic background. For example, survival upon infection and female fecundity exhibited differences in 50% and 40% of the tested isogenic vs. non-isogenic pairs, respectively, whereas all other phenotypes were affected in only 10-25% of the cases. We also observed that the genetic background affects Gal4 transgenes unpredictably. Thus, depending on the trait of interest, the genetic background of commonly used transgenic strains needs to be considered carefully during experimentation.

genetics↗

bioRxiv2019

Changing environments and genetic variation: inbreeding does not compromise short-term physiological responses

O_LISelfing plant lineages are surprisingly widespread and successful in a broad range of environments, despite showing reduced genetic diversity, which is predicted to reduce long-term evolutionary potential. However, short-term capacity to respond appropriately to new conditions might not require high levels of standing genetic variation. The purpose of this study was to directly test whether mating system variation and its associated changes in genetic variability in natural populations affected responses to short-term environmental challenges.\nC_LIO_LIWe compared relative fitness and metabolome profiles of naturally outbreeding (genetically diverse) and inbreeding (genetically depauperate) populations of a long-lived perennial plant, Arabidopsis lyrata, under constant growth chamber conditions and an outdoor common garden environment outside its native range.\nC_LIO_LIWe found no effect of mating system on survival or reproductive output, although several phenological traits showed different associations with latitude for outcrossing and inbreeding populations. Natural inbreeding had no effect on the plasticity of physiological responses, using either multivariate approaches or analysis of variation in individual metabolites. Moreover, while both growing environment and time significantly affected the relative abundance of individual metabolites, inbreeding populations responded similarly to outbreeding populations, suggesting adaptation to the outdoor environment, regardless of mating system.\nC_LIO_LIWe conclude that low genetic diversity in naturally inbred populations may not compromise fitness or short-term capacity for appropriate physiological responses to environmental change. The absence of natural costs of inbreeding could help to explain the global success of clonal or asexual mating strategies for adapting to a wide range of environments.\nC_LI

evolutionary biology↗

bioRxiv2019

Corazonin neuroendocrine pathway orchestrates stress-associated physiology in Drosophila

Environmental factors challenge the physiological homeostasis in animals, thereby evoking stress responses. Various mechanisms have evolved to counter stress at the organism level, including regulation by neuropeptides. In recent years, much progress has been made on the mechanisms and neuropeptides that regulate responses to metabolic/nutritional stress, as well as those involved in countering osmotic and ionic stresses. Here, we identified a peptidergic pathway that links these types of regulatory functions. We uncover the neuropeptide Corazonin (Crz), previously implicated in responses to metabolic stress, as a neuroendocrine factor that inhibits the release of a diuretic hormone, CAPA, and thereby modulates the tolerance to osmotic and ionic stress. Both knockdown of Crz and acute injections of Crz peptide impact desiccation tolerance and recovery from chill-coma. Mapping of the Crz receptor (CrzR) expression identified three pairs of Capa-expressing neurons (Va neurons) in the ventral nerve cord that mediate these effects of Crz. We show that Crz acts to restore water/ion homeostasis by inhibiting release of CAPA neuropeptides via inhibition of cAMP production in Va neurons. Knockdown of CrzR in Va neurons affects CAPA signaling, and consequently increases tolerance for desiccation, ionic stress and starvation, but delays chill-coma recovery. Optogenetic activation of Va neurons stimulates excretion and simultaneous activation of Crz and CAPA-expressing neurons reduces this response, supporting the inhibitory action of Crz. Thus, Crz inhibits Va neurons to maintain osmotic and ionic homeostasis, which in turn affects stress tolerance. Earlier work demonstrated that systemic Crz signaling restores nutrient levels by promoting food search and feeding. Here we additionally propose that Crz signaling also ensures osmotic homeostasis by inhibiting release of CAPA neuropeptides and suppressing diuresis. Thus, Crz ameliorates stress-associated physiology through systemic modulation of both peptidergic neurosecretory cells and the fat body in Drosophila. Author summaryInsects are among the largest groups of animals and have adapted to inhabit almost all environments on Earth. Their success in surviving extreme conditions stems largely from their ability to withstand environmental stress, such as desiccation and cold. However, the neural mechanisms that are responsible for coordinating responses to counter these stresses are largely unknown. To address this, we delineate a neuroendocrine axis utilizing the neuropeptides Corazonin (Crz) and CAPA, that coordinate responses to metabolic and osmotic stress. We show that Crz inhibits the release of a diuretic peptide, CAPA from a set of neurosecretory cells. CAPA in turn influences osmotic and ionic balance via actions on the Malpighian tubules (the insect analogs of the kidney) and the intestine. Taken together with earlier work, our data suggest that Crz acts to restore metabolic homeostasis at starvation and osmotic homeostasis during desiccation by inhibiting release of the diuretic hormone CAPA. Hence, this work provides a mechanistic understanding of the neuroendocrine mitigation of metabolic and osmotic stress by two peptide systems.

neuroscience↗

bioRxiv2019

Tubulin mRNA stability is sensitive to change in microtubule dynamics caused by multiple physiological and toxic cues

The localization, mass, and dynamics of microtubules are important in many processes. Cells may actively monitor the state of their microtubules and respond to perturbation, but how this occurs outside mitosis is poorly understood. We used gene expression analysis in quiescent cells to analyze responses to subtle and strong perturbation of microtubules. Genes encoding -, {beta}, and {gamma}-tubulins, but not {delta}- or {varepsilon}-tubulins, exhibited the strongest differential expression response to microtubule-stabilizing versus destabilizing drugs. Q-PCR of exon versus intron sequences confirmed that these changes were caused by regulation of tubulin mRNA stability and not transcription. Using tubulin mRNA stability as a signature to query the GEO database, we find that tubulin genes respond to toxins known to damage microtubules. Importantly, we find many other experimental perturbations, including multiple signaling and metabolic inputs that trigger tubulin differential expression, suggesting their novel role in the regulation of microtubule cytoskeleton. Mechanistic follow up confirms that one important physiological signal, phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) activity, indeed regulates tubulin mRNA stability via changes in microtubule dynamics. We propose that that tubulin gene expression is regulated as part of many coordinated biological responses, with wide implications in physiology and toxicology. Furthermore, we present a new way to discover microtubule regulation using genomics.

cell biology↗

bioRxiv2019

The International Space Station selects for microorganisms adapted to the extreme environment, but does not induce genomic and physiological changes relevant for human health

The International Space Station (ISS) is a unique, completely confined habitat for the human crew and co-inhabiting microorganisms. Here, we report on the results of the ISS experiment "EXTREMOPHILES". We aimed to exploit the microbial information obtained from three surface and air sampling events aboard the International Space Station during increments 51 and 52 (2017) with respect to: i) microbial sources, diversity and distribution within the ISS, ii) functional capacity of microbiome and microbial isolates, iii) extremotolerance and antibiotics-resistance (compared to ground controls), and iv) microbial behavior towards ISS-relevant materials such as biofilm formation, or potential for degradation. We used wipe samples and analyzed them by amplicon and metagenomics sequencing, cultivation, comparative physiological studies, antibiotic resistance tests, genome analysis of isolates and co-incubation experiments with ISS-relevant materials. The major findings were: i) the ISS microbiome profile is highly similar to ground-based confined indoor environments, ii) the ISS microbiome is subject to fluctuations and indicative for the (functional) location, although a core microbiome was present over time and independent from location, iii) the ISS selects for microorganisms adapted to the extreme environment, but does not necessarily induce genomic and physiological changes which might be relevant for human health, iv) cleanrooms and cargo seems to be a minor source of microbial contamination aboard, and v) microorganisms can attach to and grow on ISS-relevant materials. Biofilm formation might be a threat for spacecraft materials with the potential to induce instrument malfunctioning with consequences for mission success. We conclude that our data do not raise direct reason for concern with respect to crew health, but indicate a potential threat towards biofilm formation and material integrity in moist areas.

microbiology↗

bioRxiv2019

Physiological and Evolutionary Implications of Tetrameric Photosystem I in Cyanobacteria

Photosystem I (PSI) were reported as trimeric complexes in most characterized cyanobacteria, yet monomers in plants and algae PSI. Recent reports on tetrameric PSI raised questions regarding its structural basis, physiological role, phylogenetic distribution and evolutionary significance. In this study, by examining PSI in 61 cyanobacteria, we show that tetrameric PSI, correlating with a unique psaL gene and genomic structure, is widespread in the heterocyst-forming cyanobacteria and their close relatives. Physiological studies on these cyanobacteria revealed that tetrameric PSI is favored under high light, with an increased content of novel PSI-bound carotenoids (myxoxanthophyll, canthaxanthan and echinenone). Together this work suggests that tetrameric PSI is an adaptation to high light, along with results showing that change in PsaL leads to trimeric PSI monomerization, supporting the hypothesis of tetrameric PSI being the evolutionary intermediate in the transition from cyanobacterial trimeric PSI to monomeric PSI in plants and algae.

evolutionary biology↗

bioRxiv2019

Allometric Scaling of physiologically-relevant organoids

The functional and structural resemblance of organoids to mammalian organs suggests that they might follow the same allometric scaling rules. However, despite their remarkable likeness to downscaled organs, non-luminal organoids are often reported to possess necrotic cores due to oxygen diffusion limits. To assess their potential as physiologically relevant in vitro models, we determined the range of organoid masses in which quarter power scaling as well as a minimum threshold oxygen concentration is maintained. Using data on brain organoids as a reference, computational models were developed to estimate oxygen consumption and diffusion at different stages of growth. The results show that mature brain (or other non-luminal) organoids generated using current protocols must lie within a narrow range of masses to maintain both quarter power scaling and viable cores. However, micro-fluidic oxygen delivery methods could be designed to widen this range, ensuring a minimum viable oxygen threshold throughout the constructs and mass dependent metabolic scaling. The results provide new insights into the significance of the allometric exponent in systems without a resource-supplying network and may be used to guide the design of more predictive and physiologically relevant in vitro models, providing an effective alternative to animals in research.

bioengineering↗

bioRxiv2019

The distinct phenotypic signatures of dispersal and stress in an arthropod model: from physiology to life history

Dispersing individuals are expected to encounter costs during transfer and in the novel environment, and may also have experienced stress in their natal patch. Given this, a non-random subset of the population should engage in dispersal and eventually show divergent stress-related responses towards new conditions. Dispersal allows escape from stress, but is equally subjecting individuals to it.\n\nPhysiological shifts expressed in the metabolome form a major part of responses to stress exposure and are expected to be associated with the dispersal phenotype, thereby shaping physiological dispersal syndromes. We analyzed how metabolic profiles and life-history traits varied between dispersers and residents of the model two-spotted spider mite Tetranychus urticae, and whether and how these syndromes varied with exposure to a stressful new host plant (tomato). Regardless of the effect of host plant, we found a physiological dispersal syndrome where, relative to philopatric individuals, dispersers were characterized by lower leaf consumption rates and a lower concentration of several amino acids, indicating a potential dispersal-foraging trade-off. As a possible consequence of this lower food intake, dispersers also showed a lower reproductive performance. Responses to tomato exposure were consistent with this plant being a stressor for Tetranychus urticae, including reduced fecundity and reduced feeding by mites. Tomato-exposed mites laid larger eggs, which can be interpreted as a plastic response to food stress, increasing the likelihood of survival to maturity. Contrary to what could be expected from the costs of dispersal and stress resistance and from previous meta-population level studies, there was no interaction between dispersal status and host plant for any of the examined traits, indicating that the impacts of a new stressful host plant are equally incurred by residents and dispersers.\n\nWe thus provide novel insights in the processes that shape dispersal and the putative feedbacks on ecological dynamics in spatially structured populations.

ecology↗

bioRxiv2019

Analysis of physiological noise in quantitative cardiac magnetic resonance

PurposeTo determine the impact of imaging parameters on the temporal signal-to-noise ratio (TSNR) of quantitative cardiac magnetic resonance (MR) in humans, and to determine applicability of the physiological noise covariance (PNC) model for physiological noise (PN).\n\nMethodsWe conducted MRI experiments in four healthy volunteers, and obtained series of short-axis cardiac images acquired with snapshot balanced steady-state free precession (bSSFP) and snapshot gradient echo (GRE) using a broad range of spatial resolutions and parallel imaging acceleration factors commonly used in quantitative cardiac MR. We measured regional SNR and TSNR in these datasets and fit the measurements to the PNC model for PN, which assumes that PN scales with signal strength.\n\nResultsThe relationship between SNR and TSNR in human cardiac MR without contrast preparation was well modeled by the PNC model. SNR consistently decreased as the spatial resolution (matrix size) and acceleration factor (R) increased for both GRE and bSSFP imaging. TSNR varied linearly with SNR using GRE imaging, when SNR was low (SNR < 20), and approached an asymptotic limit using bSSFP imaging, when SNR was high (SNR > 40).\n\nConclusionsThe PNC model can be used to guide the choice of matrix size and acceleration factor to optimize TSNR in stable contrast cardiac MR, such as T2-prepared Blood-Oxygen-Level-Dependent (BOLD) and several variants of Arterial Spin Labeled (ASL) cardiac MR.

bioengineering↗

bioRxiv2019

HAVE IT, KNOW IT, BUT DO NOT SHOW IT: EXAMINING PHYSIOLOGICAL AROUSAL, ANXIETY, AND FACIAL EXPRESSIONS OVER THE COURSE OF A SOCIAL SKILLS INTERVENTION FOR AUTISTIC ADOLESCENTS

Facial expressions provide a nonverbal mechanism for social communication, a core challenge for autistic people. Little is known regarding the association between arousal, self-report of anxiety, and facial expressions among autistic adolescents. Therefore, this study investigated session-by-session facial expressions, self-report of anxiety, and physiological arousal via Electrodermal Activity (EDA), of 12 autistic male adolescents in a didactic social skills intervention setting. The goals of this study were threefold: 1) identify physiological arousal levels (\"have-it\"), 2) examine if autistic adolescents facial expressions indicated arousal (\"show-it\"), and 3) determine whether autistic adolescents were self-aware of their anxiety (\"know-it\"). Our results showed that autistic adolescents self-rated anxiety was significantly associated with peaks in EDA. Both machine learning algorithms and human participant-based methods, however, had low accuracy in predicting autistic adolescents arousal state from facial expressions, suggesting that autistic adolescents facial expressions did not coincide with their arousal. Implications for understanding social communication difficulties among autistic adolescents, as well as future targets for intervention, are discussed. This project is registered with ClinicalTrials.gov, Identifier: NCT02680015.

bioinformatics↗

bioRxiv2019

Genetic Mapping Of Morpho-Physiological Traits Involved During Reproductive Stage Drought Tolerance In Rice

Reproductive stage drought stress is an important factor for yield reduction in rice. Genetic mapping of drought responsive QTLs will help to develop cultivars suitable for drought prone environments through marker-assisted breeding. QTLs linked to morpho-physiological traits under drought stress were mapped by evaluating 190 F7 recombinant inbred lines (RIL). Significant variations were observed for eleven morpho-physiological traits involved during the stress. Bulked segregant analysis (BSA) strategy was adopted for genotyping the RIL population. A total of 401 SSR primers were tested for parental polymorphism of which 77 were polymorphic. Inclusive composite interval mapping detected a total of five consistent QTLs controlling leaf rolling (qLR9.1), leaf drying (qLD9.1), harvest index (qHI9.1), spikelet fertility (qSF9.1) and relative water content (qRWC9.1) under reproductive stage drought stress. Another two non-allelic QTLs controlling leaf rolling (qLR8.1) and leaf drying (qLD12.1) were linked in a single year. QTL controlling leaf rolling, qLR8.1 was validated in this mapping population and useful in marker-assisted breeding (MAB) programs. Out of these five consistent QTLs, four (qLR9.1, qLD9.1, qHI9.1 and qRWC9.1) were detected to be novel QTLs and useful for MAB for reproductive stage drought tolerance in rice.

genetics↗

bioRxiv2019

Flexible connectivity under physiological constraints.

Neural computation is determined by neuron dynamics and circuit connectivity. Uncertain and dynamic environments may require neural hardware to adapt to different computational tasks, each requiring different connectivity configurations. At the same time, connectivity is subject to a variety of constraints, placing limits on the possible computations a given neural circuit can perform. Here we examine the hypothesis that the organization of neural circuitry favors computational flexibility: that it makes many computational solutions available, given physiological constraints. From this hypothesis, we develop models of the degree distributions of connectivity based on constraints on a neurons total synaptic weight. To test these models, we examine reconstructions of the mushroom bodies from the first instar larva and the adult Drosophila melanogaster. We perform a Bayesian model comparison for two constraint models and a random wiring null model. Overall, we find that flexibility under a homeostatically fixed total synaptic weight describes Kenyon cell connectivity better than other models, suggesting a principle shaping the apparently random structure of Kenyon cell wiring. Furthermore, we find evidence that larval Kenyon cells are more flexible earlier in development, suggesting a mechanism whereby neural circuits begin as flexible systems that develop into specialized computational circuits. Author summaryHigh-throughput electron microscopic anatomical experiments have begun to yield detailed maps of neural circuit connectivity. Uncovering the principles that govern these circuit structures is a major challenge for systems neuroscience. Healthy neural circuits must be able to perform computational tasks while satisfying physiological constraints. Those constraints can restrict a neurons possible connectivity, and thus potentially restrict its computation. Here we examine simple models of constraints on total synaptic weights, and calculate the number of circuit configurations they allow: their computational flexibility. We propose probabilistic models of connectivity that weight the number of synaptic partners according to computational flexibility under a constraint and test them using recent wiring diagrams from a learning center, the mushroom body, in the fly brain. We compare constraints that fix or bound a neurons total connection strength to a simple random wiring null model. Of these models, the fixed total connection strength matched the overall connectivity best in mushroom bodies from both larval and adult flies. We also provide evidence suggesting that neural circuits are more flexible in early stages of development and lose this flexibility as they grow towards specialized function.

neuroscience↗

bioRxiv2019

Escherichia coli’s physiology can turn membrane voltage dyes into actuators

The electrical membrane potential (Vm) is one of the components of the electrochemical potential of protons across the biological membrane (proton motive force), which powers many vital cellular processes, and Vm also plays a role in signal transduction. Therefore, measuring it is of great interest, and over the years a variety of techniques has been developed for the purpose. In bacteria, given their small size, Nernstian membrane voltage probes are arguably the favourite strategy, and their cytoplasmic accumulation depends on Vm according to the Nernst equation. However, a careful calibration of Nernstian probes that takes into account the trade-offs between the ease with which the signal from the dye is observed, and the dyes interactions with cellular physiology, is rarely performed. Here we use a mathematical model to understand such trade-offs and, based on the knowledge gained, propose a general work-flow for the characterization of Nernstian dye candidates. We demonstrate the work-flow on the Thioflavin T dye in Escherichia coli, and identify conditions in which the dye turns from a Vm probe into an actuator.\n\nSIGNIFICANCE STATEMENT\n\nThe phospholipid bilayer of a biological membrane is virtually impermeable to charged molecules. Much like in a rechargeable battery, cells harness this property to store an electrical potential that fuels life reactions but also transduces signals. Measuring this electrical potential, also referred to as membrane voltage, is therefore of great interest and a variety of techniques have been employed for the purpose, starting as early as the 1930s. For the case of bacteria, which are smaller in size and possess a stiffer cell wall, arguably the most popular approach to measuring membrane voltage are Nernstian probes that accumulate across the bacterial membrane according to the Nernst potential. The present study characterizes the undesired effects Nernstian probes can have on cell physiology, which can be crucial for the accurate interpretation of experimental results. Using mathematical modelling and experiments, the study provides a general, simple workflow to characterise and minimise these effects.

biophysics↗

bioRxiv2019

Interspecies interactions in a model, mixed-species biofilm are determined by physiological traits and environmental factors

Interspecies interactions in bacterial biofilms have important impacts on the composition and function of communities in natural and engineered systems. To investigate these interactions, synthetic communities provide experimentally tractable systems. Agar-surface colonies are similar to biofilms and have been used for investigating the eco-evolutionary and biophysical forces that determine community composition and spatial distribution of bacteria. Prior work has focused on intraspecies interactions, using differently fluorescent tagged but identical or genetically modified strains of the same species. Here, we investigated how physiological differences determine the community composition and spatial distribution in synthetic communities of Pseudomonas aeruginosa, Pseudomonas protegens and Klebsiella pneumoniae. Using quantitative microscopic imaging, we found that interspecies interactions in multispecies colonies are influenced by type IV pilus mediated motility, extracellular matrix secretion, environmental parameters and the specific species involved. These results indicate that the patterns observable in mixed species colonies can be used to understand the mechanisms that drive interspecies interactions, which are dependent on the interplay between specific species physiology and environmental conditions.

microbiology↗

bioRxiv2019

The Psychological and Physiological Part of Emotions: Multimodal Approximation for Valence Classification

In order to develop more precise and functional affective applications, it is necessary to achieve a balance between the psychology and the engineering applied to emotions. Signals from the central and peripheral nervous systems have been used for emotion recognition purposes, however, their operation and the relationship between them remains unknown. In this context, in the present work we have tried to approach the study of the psychobiology of both systems in order to generate a computational model for the recognition of emotions in the dimension of valence. To this end, the electroencephalography (EEG) signal, electrocardiography (ECG) signal and skin temperature of 24 subjects have been studied. Each methodology has been evaluated individually, finding characteristic patterns of positive and negative emotions in each of them. After feature selection of each methodology, the results of the classification showed that, although the classification of emotions is possible at both central and peripheral levels, the multimodal approach did not improve the results obtained through the EEG alone. In addition, differences have been observed between cerebral and physiological responses in the processing emotions by separating the sample by sex; though, the differences between men and women were only notable at the physiological level.

neuroscience↗

bioRxiv2019

Dual functionality of the TasA amyloid protein in Bacillus physiology and fitness on the phylloplane

Bacteria can form biofilms that consist of multicellular communities embedded in an extracellular matrix (ECM). Previous studies have demonstrated that genetic pathways involved in biofilm formation are activated under a variety of environmental conditions to enhance bacterial fitness; however, the functions of the individual ECM components are still poorly understood. In Bacillus subtilis, the main protein component of the ECM is the functional amyloid TasA. In this study, we demonstrate that beyond their well-known defect in biofilm formation,{Delta} tasA cells also exhibit a range of cytological symptoms indicative of excessive cellular stress, including DNA damage accumulation, changes in membrane potential, higher susceptibility to oxidative stress, and alterations in membrane dynamics. Collectively, these events can lead to increased programmed cell death in the colony. We show that these major physiological changes in{Delta} tasA cells are likely independent of the structural role of TasA during amyloid fiber formation in the ECM. The presence of TasA in cellular membranes, which would place it in proximity to functional membrane microdomains, and mislocalization of the flotillin-like protein FloT in{Delta} tasA cells, led us to propose a role for TasA in the stabilization of membrane dynamics as cells enter stationary phase. We found that these alterations caused by the absence of TasA impair the survival, colonization and competition of Bacillus cells on the phylloplane. Taken together, our results allow the separation of two complementary roles of this functional amyloid protein: i) structural functions during ECM assembly and interactions with plants, and ii) a physiological function in which TasA, via its localization to the cell membrane, stabilizes membrane dynamics and supports more effective cellular adaptation to environmental cues.

microbiology↗