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Population response to global change will depend on responses to a multivariate set of changes in abiotic habitat characteristics and biotic interactions. Organismal biologists seeking to make ecological inferences about the impacts of global change by studying physiological performance have traditionally performed carefully controlled experimental studies that examine one variable at a time. Those studies, while of high value, may not lead to accurate predictions of organismal responses in the natural habitat, where organisms experience concomitant changes in multiple environmental factors. The symposium “Physiological Responses to Simultaneous Shifts in Multiple Environmental Stressors: Relevance in a Changing World” focused on physiological studies in which multiple environmental variables were simultaneously examined and brought together an international group of early-career and established speakers with unique perspectives on studies of multistressors. In doing so, the objective of the symposium was to frame the necessary next steps for increasing predictive capacity of organismal responses to environmental shifts in the natural habitat, establish novel collaborations among researchers actively investigating physiological responses to a multivariate environment, and broaden the number of researchers conducting such studies.

Engineering cell metabolism for bioproduction not only consumes building blocks and energy molecules (e.g., ATP) but also triggers energetic inefficiency inside the cell. The metabolic burdens on microbial workhorses lead to undesirable physiological changes, placing hidden constraints on host productivity. We discuss cell physiological responses to metabolic burdens, as well as strategies to identify and resolve the carbon and energy burden problems, including metabolic balancing, enhancing respiration, dynamic regulatory systems, chromosomal engineering, decoupling cell growth with production phases, and co-utilization of nutrient resources. To design robust strains with high chances of success in industrial settings, novel genome-scale models (GSMs), 13C-metabolic flux analysis (MFA), and machine-learning approaches are needed for weighting, standardizing, and predicting metabolic costs. To commercialize recombinant organisms for renewable chemical production, it is essential to characterize the cost and benefit of metabolic burden using metabolic flux analysis tools. Genome-scale modeling can incorporate 13C-fluxome information and machine learning to predict the metabolic burden of synthetic biology modules. Modularized expression of native or recombinant pathways using a variety of experimental tools for controlling expression can substantially reduce the metabolic burden introduced by these pathways. The development of a standard synthetic-biology publication database may allow the use of machine learning or artificial intelligence to harness past knowledge for future rational design. Detailed computational methods have been developed to model macromolecule synthesis (DNA, RNA, proteins) to account for the maintenance costs associated with basal cellular function. Systems-level dynamic simulations and design algorithms can inform new approaches to engineering microbial production strains.

Plant basic helix–loop–helix (bHLH) transcription factors play essential roles in abiotic stress tolerance. However, most bHLHs have not been functionally characterized. Here, we characterized the functional role of a bHLH transcription factor from Arabidopsis, AtbHLH112, in response to abiotic stress. AtbHLH112 is a nuclear-localized protein, and its nuclear localization is induced by salt, drought and abscisic acid (ABA). In addition, AtbHLH112 serves as a transcriptional activator, with the activation domain located at its N-terminus. In addition to binding to the E-box motifs of stress-responsive genes, AtbHLH112 binds to a novel motif with the sequence ‘GG[GT]CC[GT][GA][TA]C’ (GCG-box). Gain- and loss-of-function analyses showed that the transcript level of AtbHLH112 is positively correlated with salt and drought tolerance. AtbHLH112 mediates stress tolerance by increasing the expression of P5CS genes and reducing the expression of P5CDH and ProDH genes to increase proline levels. AtbHLH112 also increases the expression of POD and SOD genes to improve reactive oxygen species (ROS) scavenging ability. We present a model suggesting that AtbHLH112 is a transcriptional activator that regulates the expression of genes via binding to their GCG- or E-boxes to mediate physiological responses, including proline biosynthesis and ROS scavenging pathways, to enhance stress tolerance.

Rainfall regimes are expected to shift on a regional scale as the water cycle intensifies in a warmer climate, resulting in greater extremes in dry versus wet conditions. Such changes are having a strong impact on the agro-physiological functioning of plants that scale up to influence interactions between plants and microorganisms and hence ecosystems. In (semi)-arid ecosystems, the date palm ( Phoenix dactylifera L.) -an irreplaceable tree- plays important socio-economic roles. In the current study, we implemeted an adapted management program to improve date palm development and its tolerance to water deficit by using single or multiple combinations of exotic and native arbuscular mycorrhizal fungi (AMF1 and AMF2 respectively), and/or selected consortia of plant growth-promoting rhizobacteria (PGPR: B1 and B2), and/or composts from grasses and green waste (C1 and C2, respectively). We analyzed the potential for physiological functioning (photosynthesis, water status, osmolytes, mineral nutrition) to evolve in response to drought since this will be a key indicator of plant resilience in future environments. As result, under water deficit, the selected biofertilizers enhanced plant growth, leaf water potential, and electrical conductivity parameters. Further, the dual-inoculation of AMF/PGPR amended with composts alone or in combination boosted the biomass under water deficit conditions to a greater extent than in non-inoculated and/or non-amended plants. Both single and dual biofertilizers improved physiological parameters by elevating stomatal conductance, photosynthetic pigments (chlorophyll and carotenoids content), and photosynthetic efficiency. The dual inoculation and compost significantly enhanced, especially under drought stress, the concentrations of sugar and protein content, and antioxidant enzymes (polyphenoloxidase and peroxidase) activities as a defense strategy as compared with controls. Under water stress, we demonstrated that phosphorus was improved in the inoculated and amended plants alone or in combination in leaves (AMF2: 807%, AMF1+B2: 657%, AMF2+C1+B2: 500%, AMF2+C2: 478%, AMF1: 423%) and soil (AMF2: 397%, AMF1+B2: 322%, AMF2+C1+B2: 303%, AMF1: 190%, C1: 188%) in comparison with controls under severe water stress conditions. We summarize the extent to which the dual and multiple combinations of microorganisms can overcome challenges related to drought by enhancing plant physiological responses.

Plants use light as a source of both energy and information. Plant physiological responses to light, and interactions between plants and animals (such as herbivory and pollination), have evolved under a more or less stable regime of 24‐h cycles of light and darkness, and, outside of the tropics, seasonal variation in day length. The rapid spread of outdoor electric lighting across the globe over the past century has caused an unprecedented disruption to these natural light cycles. Artificial light is widespread in the environment, varying in intensity by several orders of magnitude from faint skyglow reflected from distant cities to direct illumination of urban and suburban vegetation. In many cases, artificial light in the night‐time environment is sufficiently bright to induce a physiological response in plants, affecting their phenology, growth form and resource allocation. The physiology, behaviour and ecology of herbivores and pollinators are also likely to be impacted by artificial light. Thus, understanding the ecological consequences of artificial light at night is critical to determine the full impact of human activity on ecosystems. Synthesis. Understanding the impacts of artificial night‐time light on wild plants and natural vegetation requires linking the knowledge gained from over a century of experimental research on the impacts of light on plants in the laboratory and glasshouse with knowledge of the intensity, spatial distribution, spectral composition and timing of light in the night‐time environment. To understand fully the extent of these impacts requires conceptual models that can (i) characterize the highly heterogeneous nature of the night‐time light environment at a scale relevant to plant physiology; and (ii) scale physiological responses to predict impacts at the level of the whole plant, population, community and ecosystem.

Therapeutic options for neurological disorders currently remain limited. The intrinsic complexity of the brain architecture prevents potential therapeutics from reaching their cerebral target, thus limiting their efficacy. Recent advances in microfluidic technology and organ-on-chip systems have enabled the development of a new generation of in vitro platforms that can recapitulate complex in vivo microenvironments and physiological responses. In this context, microfluidic-based in vitro models of the blood–brain barrier (BBB) are of particular interest as they provide an innovative approach for conducting research related to the brain, including modeling of neurodegenerative diseases and high-throughput drug screening. Here, we present the most recent advances in BBB-on-chip devices and examine validation steps that will strengthen their future applications. Microfluidic-based blood–brain barrier-on-chip (μBBB) technology is a powerful approach to study the physiological function of the BBB in vitro and to facilitate drug discovery targeting brain disorders.Mimicry of the complexity of multiple cell crosstalk and thin extracellular matrix as basal membrane are essential but challenging. Different biomaterials and chip designs have been explored in the fabrication of μBBBs.Other key features such as shear stress, cell type/origin, and cell co-culture spatial configuration must be carefully controlled and selected. Appropriate BBB permeability assays and parameters (e.g., TEER measurement, small molecule drugs, and fluorescent probes) should be standardized and compared with in vivo data.μBBBs hold great potential in disease modeling, drug discovery, neurotoxicity screening, and personalized medicine applications.

Background Abiotic stresses due to environmental factors could adversely affect the growth and development of crops. Among the abiotic stresses, drought and heat stress are two critical threats to crop growth and sustainable agriculture worldwide. Considering global climate change, incidence of combined drought and heat stress is likely to increase. The aim of this study was to shed light on plant growth performance and leaf physiology of three tomatoes cultivars (‘Arvento’, ‘LA1994’ and ‘LA2093’) under control, drought, heat and combined stress. Results Shoot fresh and dry weight, leaf area and relative water content of all cultivars significantly decreased under drought and combined stress as compared to control. The net photosynthesis and starch content were significantly lower under drought and combined stress than control in the three cultivars. Stomata and pore length of the three cultivars significantly decreased under drought and combined stress as compared to control. The tomato ‘Arvento’ was more affected by heat stress than ‘LA1994’ and ‘LA2093’ due to significant decreases in shoot dry weight, chlorophyll a and carotenoid content, starch content and NPQ (non-photochemical quenching) only in ‘Arvento’ under heat treatment. By comparison, the two heat-tolerant tomatoes were more affected by drought stress compared to ‘Arvento’ as shown by small stomatal and pore area, decreased sucrose content, Φ PSII (quantum yield of photosystem II), ETR (electron transport rate) and q L (fraction of open PSII centers) in ‘LA1994’ and ‘LA2093’. The three cultivars showed similar response when subjected to the combination of drought and heat stress as shown by most physiological parameters, even though only ‘LA1994’ and ‘LA2093’ showed decreased F v /F m (maximum potential quantum efficiency of photosystem II), Φ PSII , ETR and q L under combined stress. Conclusions The cultivars differing in heat sensitivity did not show difference in the combined stress sensitivity, indicating that selection for tomatoes with combined stress tolerance might not be correlated with the single stress tolerance. In this study, drought stress had a predominant effect on tomato over heat stress, which explained why simultaneous application of heat and drought revealed similar physiological responses to the drought stress. These results will uncover the difference and linkage between the physiological response of tomatoes to drought, heat and combined stress and be important for the selection and breeding of tolerant tomato cultivars under single and combine stress.

Summary The growth and yield of many crops, including cotton, are affected by water deficit. Cotton has evolved drought specific as well as general morpho‐physiological, biochemical and molecular responses to drought stress, which are discussed in this review. The key physiological responses against drought stress in cotton, including stomata closing, root development, cellular adaptations, photosynthesis, abscisic acid (ABA) and jasmonic acid (JA) production and reactive oxygen species (ROS) scavenging, have been identified by researchers. Drought stress induces the expression of stress‐related transcription factors and genes, such as ROS scavenging, ABA or mitogen‐activated protein kinases (MAPK) signalling genes, which activate various drought‐related pathways to induce tolerance in the plant. It is crucial to elucidate and induce drought‐tolerant traits via quantitative trait loci (QTL) analysis, transgenic approaches and exogenous application of substances. The current review article highlights the natural as well as engineered drought tolerance strategies in cotton.

Background and aims Alterations in root growth and rhizosphere processes in maize (Zea mays L.) occur under phosphorus (P) deficiency, but the dynamics of root morphological and physiological modifications with increasing shoot P concentration remain unclear. This study investigated root responses to a wide gradient in shoot P status. Methods A range of maize shoot P concentrations (1.0–4.0 mg g−1) was established using controlled pot experiment with eleven rates of P supply from 0 to 1200 mg P kg−1 soil. Root morphology and rhizosphere processes were characterized 28 days after planting. Results Maize reached maximum biomass at shoot P concentration of 2.7 mg g−1. Root morphological responses (i.e. total root length, specific root length and proportion of fine roots) showed a strong increasing trend with decreasing shoot P concentration (1.1–1.3 mg g−1), but they decreased when shoot P concentration was extremely low (below 1.1 mg g−1). In contrast, with increasing shoot P concentration, root morphological responses decreased, but root physiological responses (rhizosphere acidification, acid phosphatase activity and carboxylate exudation in the rhizosphere) were enhanced, and no decrease was noted even at high shoot P concentration (4.0 mg g−1) corresponding to excess P supply. Conclusions Increasing maize shoot P concentration induced a decrease in root morphological responses and an enhancement in root exudation, with maize response to P deficiency being dependent on root morphological rather than physiological traits.

Weed management is an arduous undertaking in crop production. Integrated weed management, inclusive of the application of bioherbicides, is an emerging weed control strategy toward sustainable agriculture. In general, bioherbicides are derived either from plants containing phytotoxic allelochemicals or certain disease-carrying microbes that can suppress weed populations. While bioherbicides have exhibited great promise in deterring weed seed germination and growth, only a few in vitro studies have been conducted on the physiological responses they evoke in weeds. This review discusses bioherbicide products that are currently available on the market, bioherbicide impact on weed physiology, and potential factors influencing bioherbicide efficacy. A new promising bioherbicide product is introduced at the end of this paper. When absorbed, phytotoxic plant extracts or metabolites disrupt cell membrane integrity and important biochemical processes in weeds. The phytotoxic impact on weed growth is reflected in low levels of root cell division, nutrient absorption, and growth hormone and pigment synthesis, as well as in the development of reactive oxygen species (ROS), stress-related hormones, and abnormal antioxidant activity. The inconsistency of bioherbicide efficacy is a primary factor restricting their widespread use, which is influenced by factors such as bioactive compound content, weed control spectrum, formulation, and application method.