Carbon Fixation Research Articles

Navigating the microalgal maze: a comprehensive review of recent advances and future perspectives in biological networks.

PPI analysis deepens our knowledge in critical processes like carbon fixation and nutrient sensing. Moreover, signaling networks, including pathways like MAPK/ERK and TOR, provide valuable information in how microalgae respond to environmental changes and stress. Additionally, species-species interaction networks for microalgae provide a comprehensive understanding of how different species interact within their environments. This review examines recent advancements in the study of biological networks within microalgae, with a focus on the intricate interactions that define these organisms. It emphasizes how network biology, an interdisciplinary field, offers valuable insights into microalgae functions through various methodologies. Crucial approaches, such as protein-protein interaction (PPI) mapping utilizing yeast two-hybrid screening and mass spectrometry, are essential for comprehending cellular processes and optimizing functions, such as photosynthesis and fatty acid biosynthesis. The application of advanced computational methods and information mining has significantly improved PPI analysis, revealing networks involved in critical processes like carbon fixation and nutrient sensing. The review also encompasses transcriptional networks, which play a role in gene regulation and stress responses, as well as metabolic networks represented by genome-scale metabolic models (GEMs), which aid in strain optimization and the prediction of metabolic outcomes. Furthermore, signaling networks, including pathways like MAPK/ERK and TOR, are crucial for understanding how microalgae respond to environmental changes and stress. Additionally, species-species interaction networks for microalgae provide a comprehensive understanding of how different species interact within their environments. The integration of these network biology approaches has deepened our understanding of microalgal interactions, paving the way for more efficient cultivation and new industrial applications.

New insight into Clostridium butyricum-ferroferric oxide hybrid system in exogenous carbon dioxide-assisted anaerobic fermentation for acetate and butyrate production

Mixotrophic cultivation, utilizing both gas and organic substances, is commonly employed to minimize the carbon loss during anaerobic fermentation of bulk chemicals. Herein, a novel Clostridium butyricum-ferroferric oxide (Fe3O4) hybrid system, enhanced by exogenous carbon dioxide (CO2), was proposed to improve carbon recovery and optimize metabolite production. The results demonstrated that exogenous CO2 improved metabolite selectivity towards acetate/butyrate, while also accelerating CO2 fixation. Compared to pure Clostridium butyricum, the hybrid system significantly increased carbon conversion to primary metabolites, boosting butyrate and acetate production by 18.7 % and 18.4 %, respectively. Enzyme activity assays revealed that Fe3O4 and exogenous CO2 acted synergistically, enhancing the activities of key enzymes involved in CO2 assimilation. Additionally, Fe3O4 facilitated intra- and extracellular electron transfer, further improving the fermentation process. This study offers new insights into the combined effects of exogenous CO2 and Fe3O4 on anaerobic fermentation, providing an efficient strategy for carbon recovery and selective acetate/butyrate production.

Microbial mechanisms for CO2 and CH4 emissions in Robinia pseudoacacia forests along a North–South transect in the Loess Plateau

Forest soil microbes play a crucial role in regulating atmospheric-soil carbon fluxes. Environmental heterogeneity across forest types and regions may lead to differences in soil CO2 and CH4 emissions. However, the microbial mechanisms underlying these emission variations are currently unclear. In this study, we measured CO2 and CH4 emissions of Robinia pseudoacacia forests along a north–south transect in the Loess Plateau. Using metagenomic sequencing, we investigated the structural and functional profiles of soil carbon cycling microbial communities. Results indicated that the forest CO2 emissions of Robinia pseudoacacia was significantly higher in the north region than in the south region, while the CH4 emission was oppositely. This is mainly attributed to changes in gene abundance driven by soil pH and moisture in participating carbon degradation and methane oxidation processes across different forest regions. The gene differences in carbon fixation processes between regions primarily stem from the Calvin cycle, where the abundance of rbcL, rbcS, and prkB genes dominates microbial carbon fixation in forest soils. Random forest models revealed key genes involved in predicting forest soil CO2 emissions, including SGA1 and amyA for starch decomposition, TYR for lignin decomposition, chitinase for chitin decomposition, and pectinesterase for pectin decomposition. Microbial functional characterization revealed that interregional differences in CH4 emissions during methane metabolism may originate from methane oxidation processes, and the associated gene abundances (glyA, ppc, and pmoB) were key genes for predicting CH4 emissions from forest soils. Our results provide new insights into the microbial mechanisms of CO2 and CH4 emissions from forest soils, which will be crucial for accurate prediction of the forest soil carbon cycle in the future.

Elucidating the downstream pathways triggered by H2S signaling in Arabidopsis thaliana under drought stress via transcriptome analysis

ABSTRACT Hydrogen sulfide (H2S) is a crucial signaling molecule in plants. Recent studies have shown that H2S plays an equally important role as nitric oxide (NO) and hydrogen peroxide (H2O2) in plant signaling. Previous studies have demonstrated the involvement of H2S in regulating drought and other stressful environmental conditions, but the exact downstream molecular mechanisms activated by the H2S signaling molecule remain unclear. In this study, we conducted a comprehensive genome-wide transcriptomic analysis of both wild type (WT) and double mutant (lcd/des1). Arabidopsis thaliana plants were exposed to 40% polyethylene glycol (PEG) to induce drought stress and 20 µM sodium hydrosulfide (NaHS). The resulting transcriptome data were analyzed for differentially significant genes and their statistical enrichments in the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. The results indicated significant upregulation of genes related to photosynthesis, carbon fixation, plant secondary metabolite biosynthesis, inositol and phosphatidylinositol signaling pathways, and stress-responsive pathways in mutant plants under drought stress. Mutant plants with impaired H2S signaling mechanisms displayed greater susceptibility to drought stress compared to wild-type plants. In summary, all findings highlight the pivotal role of H2S signaling in stimulating other drought-responsive signaling pathways.

Integrating Deficit Irrigation Strategies and Soil-Management Systems in Almond Orchards for Resilient Agriculture

This work was conducted over three-year monitoring seasons of three almond cultivars (Guara, Marta, and Lauranne) subjected to deficit irrigation in combination with cover crops in a Mediterranean semiarid area (SW, Spain). Four water–soil treatments were evaluated based on the conjunction of two irrigation strategies: fully irrigated (FI), covering 100% of the ETC, and regulated deficit irrigation (RDI), with two soil-management systems: bare soil (BS) and cover crop based on a mixture of vetch (Vicia sativa L.) and oat (Avena sativa L.) (CC). Throughout the study period in trees, the yield, the stem water potential (Ψstem), leaf nutrient content (N, P, K, Ca, Mg, Na, Fe, Zn, Mn, and Cu) in soils, organic carbon, microbial biomass, fluoresceine diacetate, and enzymatic activities (dehydrogenase, protease, β-glucosidase, and alkaline phosphatase) were determined. In addition, the dry matter and carbon fixation by plant covers were evaluated. For Guara and Lauranne, yield reductions (22 and 26%, respectively) were found for water-stressed (RDI-CC) plots with respect to non-stressed combination (FI-CC) plots, contrasting with cv. Marta, without a significant impact on productivity in all combinations. That is, the RDI (~3.000 m3 ha−1) strategy enabled acceptable productivity, offering promising possibilities for cultivation performance under water-scarcity scenarios. Important differences in Ψstem could be observed and ascribed to irrigation strategies, especially for Guara and Lauranne, but without significant effects due to the soil-management systems applied. No differences were observed in the tree nutritional status due to the presence or absence of CC; however, its presence increased the fixation of atmospheric carbon, which was not the case under BS conditions. Additionally, CC significantly fostered the microbial processes and enzymatic activities, particularly in upper soil layers (0–10 cm) and with plenty of water supply in FI-CC plots and to a lesser extent in RDI-CC plots, which could encourage prominent aspects for soil quality and health restoration. Thus, the cover crop is congruent with RDI to facilitate soil functionality and water savings in a changing climate, contributing to resilient farming systems in the Mediterranean environment.

Acute toxicity of salicylic acid and its derivatives on the diatom Phaeodactylum tricornutum: Physico-Biochemical and transcriptomic insights

Salicylate pollutants (SAs) poses a serious threat to marine ecosystems as emerging contaminants. However, the toxic effects of SAs on marine phytoplankton, as well as the potential mechanisms and their ecological risks linked with them, are remain largely unknown. In this study, we aimed to evaluate the toxic effects of salicylic acid (SA) and its 5-substituted derivatives (5-sSA) on the marine diatom Phaeodactylum tricornutum, as well as the potential molecular mechanism involved in the toxicity. Physiological assays conducted on P. tricornutum revealed significant changes in photosynthetic pigments, chlorophyll fluorescence parameters, and antioxidant enzyme activities. The results showed that exposure of P. tricornutum to SAs caused a significant decline in chlorophyll contents and damage to the photosystem II (PSII) core resulting in the decline of photosynthesis. Although the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were enhanced, oxidative damage occurred. Transcriptome analysis showed that a large number of differentially expresses genes (DEGs) were significantly enriched in metabolic pathways such as porphyrin metabolism, terpenoid backbone biosynthesis, and carbon fixation in photosynthetic organisms after SA and 5-BrSA treatments. In addition, key genes in transcriptomic metabolic pathways were further analyzed and validated using weighted correlation network analysis (WGCNA) and real-time fluorescence quantitative PCR (qPCR). Considering the above results, SAs mainly inhibit the processes of photosynthesis by repressing the expression of genes involved in secondary metabolite synthesis and photosynthetic carbon sequestration pathways, thus exerting toxic effects on algal cells. The results of the study will provide key data for understanding the ecological risk and toxicity mechanisms of SA pollutants.

A LysR-type regulator influencing swimming motility, galactose utilization, and virulence in Ralstonia solanacearum GMI1000

BackgroundLysR-type transcriptional regulators (LTTRs) are one of the largest families of regulators in prokaryotic organism, which help the bacterium adapt to diverse conditions by controlling a wide array of regulons, encompassing genes responsible for nitrogen and carbon fixation, oxidative stress response, bacterial virulence, and the breakdown of diverse compounds. Ralstonia solanacearum strain GMI1000 possesses 80 LTTR genes, yet the precise roles and functional contributions of only three of these LTTRs have been conclusively established among the total. In this work, our group reveal a novel LTTR member LysR7 (RS_RS02375) that exerts multiple regulatory roles in motility, carbon metabolism and virulence.ResultsIn this investigation, an in-frame deletion mutant ΔlysR7 and a complemented strain CΔlysR7 were prepared. The mutant ΔlysR7 had increased swimming motility on semi-soft medium and showed a reduced replication rate in nutrient-rich medium and in planta. Moreover, ΔlysR7 was unable to grow on nutrient-limited medium, supplemented with galactose as a single carbon resource. RT-qPCR analysis and GUS activity detection indicated that the expression of lysR7 was induced in the presence of galactose. The mutant ΔlysR7 caused weaker wilt disease on either Solanum lycopersicum or Capsicum annuum plants compared to both wild type GMI1000 and CΔlysR7. Transcriptome analysis revealed that 12 upregulated and 8 downregulated differentially expressed genes (DEGs) in ΔlysR7 were restored in CΔlysR7 relative to wild type. In particular, the expression of hrpG, a key gene responsible for type III secretion system, was downregulated. KEGG analysis revealed that, except for lysR7 gene, the 19 DEGs were most enriched in microbial metabolism in diverse environments and metabolic pathways.ConclusionsThe data indicate that LysR7 regulates multiple processes in association with motility, galactose metabolism and virulence in R. solanacearum. The study offers valuable evidence to understand comprehensive regulatory mechanisms mediated by LTTR family members in R. solanacearum.Graphical

Hydrothermal vents supporting persistent plumes and microbial chemoautotrophy at Gakkel Ridge (Arctic Ocean).

Hydrothermal vents emit hot fluids enriched in energy sources for microbial life. Here, we compare the ecological and biogeochemical effects of hydrothermal venting of two recently discovered volcanic seamounts, Polaris and Aurora of the Gakkel Ridge, in the ice-covered Central Arctic Ocean. At both sites, persistent hydrothermal plumes increased up to 800 m into the deep Arctic Ocean. In the two non-buoyant plumes, rates of microbial carbon fixation were strongly elevated compared to background values of 0.5-1 μmol m-3 day-1 in the Arctic deep water, which suggests increased chemoautotrophy on vent-derived energy sources. In the Polaris plume, free sulfide and up to 360 nM hydrogen enabled microorganisms to fix up to 46 μmol inorganic carbon (IC) m-3 day-1. This energy pulse resulted in a strong increase in the relative abundance of SUP05 by 25% and Candidatus Sulfurimonas pluma by 7% of all bacteria. At Aurora, microorganisms fixed up to 35 μmol IC m-3 day-1. Here, metal sulfides limited the bioavailability of reduced sulfur species, and the putative hydrogen oxidizer Ca. S. pluma constituted 35% and SUP05 10% of all bacteria. In accordance with this data, transcriptomic analysis showed a high enrichment of hydrogenase-coding transcripts in Aurora and an enrichment of transcripts coding for sulfur oxidation in Polaris. There was neither evidence for methane consumption nor a substantial increase in the abundance of putative methanotrophs or their transcripts in either plume. Together, our results demonstrate the dominance of hydrogen and sulfide as energy sources in Arctic hydrothermal vent plumes.

Effects of manure and nitrogen fertilization on soil microbial carbon fixation genes and associated communities in the Loess Plateau of China

The effects of long-term fertilization on soil carbon (C) cycling have been a key focus of agricultural sustainable development research. However, the influences of different fertilization treatments on soil microbial C fixation profiles are still unclear. Metagenomics technology and multivariate analysis were employed to inquire changes in soil properties, soil microbial C fixation genes and associated bacterial communities, and the influence of dominant soil properties on C fixation genes. The contents of soil C and nitrogen fractions were signicficantly higher in manure or combined with nitrogen fertilization (NM) than other treatments. The composition of soil microbial C fixation genes and associated bacterial communities varied among different fertilization treatments. Compared with other treatments, the total abundance of microbial C fixation genes and the abundance of Proteobacteria were significantly higher in NM than in other treatments, as well as the abundances of C fixation genes involved in dicarboxylate/4-hydroxybutyrate cycle and reductive citrate cycle. Key functional genes and main bacterial communities presented in the middle of the co-occurrence network. Soil organic carbon, total nitrogen, and microbial biomass nitrogen were the dominant soil properties influencing microbial C fixation genes and associated bacterial communitis. Fertilization increased the abundance of C fixation genes by affecting the changes in bacterial communities abundance mediated by soil properties. Overall, elucidating the responses of soil microbial C fixation genes and associated communities to different fertilization will enhance our understanding of the processes of soil C fixation in farmland.

Hydrazino-containing Zr-MOF for enhanced Lewis acid-base catalysis of CO2 fixation into cyclocarbonate

Developing an effective catalyst for converting CO2 into high-value chemicals is greatly desirable but remains a big hurdle. Herein, Zr-MOF derivative-bearing hydrazino groups were synthesized by mixing the ligands of terephthalic acid and 4-hydrazinobenzoic acid (HBA), resulting in UiO-66-HBA as heterocatalyst for epoxide cycloaddition with CO2. Compared to UiO-66, the optimal UiO-66-HBA0.2 displayed outstanding activity for epichlorohydrin cycloaddition, with 96.03 % cyclocarbonate yield under 0.1 MPa CO2 at 70 ℃. The great activity of UiO-66-HBA0.2 was attributed to the synergistic cooperation of Lewis base offered by HBA moiety and Lewis acid originated from Zr6 clusters, which was affirmed by NH3/CO2-temperature-programmed desorption experiments and CO2 adsorption isotherms. Moreover, UiO-66-HBA0.2 exhibited excellent stability and great substrate compatibility. In addition, a possible mechanism for catalyzing CO2 conversion into cyclocarbonate was suggested. This study provides an effective way to design functionalized MOFs-based heterocatalysts for CO2 utilization.

A synthesis of research on the sequestration of carbon in forests and the conservation of water

Forests help solve environmental issues by sequestering carbon and conserving water. Forest management's ultimate goal is to optimize dual functions to reduce greenhouse gas emissions and maintain the water cycle. Increased forest production and ecosystem water balance have costs and benefits. This study reviews forest carbon sequestration and hydrological principles for future research. The interaction between forest carbon sequestration and water conservation revealed information gaps and research needs. Previous research has helped comprehend forest carbon fixing and hydrological regulation. Many equipment and methods can quantify and monitor forest carbon and hydrological issues at multiple geographical and temporal levels. Afforestation programs that improve carbon sequestration and water maintenance ecosystem services lack knowledge. Top-down scheduling of afforestation in locations with uncertain water supplies must address how much and where to plant assumed existing land, ecological implications, and local progress and income. Planting decisions dominate local management. Cooperative research is needed to build and manage planted forests for carbon sequestration, water management, and other societal purposes. This study's integrated paradigm for forest management considers carbon sequestration and water conservation can assist future research.

Diatom pyrenoids are encased in a protein shell that enables efficient CO2 fixation

Pyrenoids are subcompartments of algal chloroplasts that increase the efficiency of Rubisco-driven CO2 fixation. Diatoms fix up to 20% of global CO2, but their pyrenoids remain poorly characterized. Here, we used invivo photo-crosslinking to identify pyrenoid shell (PyShell) proteins, which we localized to the pyrenoid periphery of model pennate and centric diatoms, Phaeodactylum tricornutum and Thalassiosira pseudonana. In situ cryo-electron tomography revealed that pyrenoids of both diatom species are encased in a lattice-like protein sheath. Single-particle cryo-EM yielded a 2.4-Å-resolution structure of an invitro TpPyShell1 lattice, which showed how protein subunits interlock. T.pseudonana TpPyShell1/2 knockout mutants had no PyShell sheath, altered pyrenoid morphology, and a high-CO2 requiring phenotype, with reduced photosynthetic efficiency and impaired growth under standard atmospheric conditions. The structure and function of the diatom PyShell provide a molecular view of how CO2 is assimilated in the ocean, a critical ecosystem undergoing rapid change.

Kinetics model with experimental validation for optimal microalgae generation in double-skin façades

Microalgae photobioreactors integrated into double-skin façades in cold climates enhance growth conditions for biomass generation, CO2 fixation, and O2 production, while reducing thermal loads. However, shading imposed by double-skin façade's assembly limits light interception for the photobioreactors. This study employs kinetics and shading models to estimate variations in biomass concentration within the light-constrained photobioreactor. To validate the accuracy and reliability of the model, the results were compared to experimental data collected by the authors from a full-scale constructed system. Biomass concentration was monitored using a developed RGB image-based monitoring technique. Direct search methods were employed to optimize the design and operational variables of the microalgae photobioreactors, with the goal of maximizing annual areal and volumetric productivities across 14 Canadian cities under various climatic conditions. Hooke-Jeeves algorithm was 65.6 % faster than Powell's conjugate direction method. This showed the system's adaptability by generating 1.3–3.0 kg/m2.year of biomass in different climates. The study established a framework for optimizing microalgae photobioreactors into façades to maximize biomass harvest.

The transcription factor TaNF-YB4 overexpression in wheat increases plant vigor and yield

Ensuring food security is a priority in developing countries. This study aimed to improve wheat yield by overexpressing the TaNF-YB4 transcription factor, which is involved in carbon assimilation and stress tolerance. An expression cassette for TaNF-YB4 was developed in a modified wheat transformation vector (pSB219) and examined through transient expression in Nicotiana tabacum, followed by Agrobacterium-mediated transformation of wheat variety FSD-2008. T0 transgenic plants were propagated to obtain T3 generation PCR-positive plants. Transgene expression was assessed in PCR-verified T2 plants using RT-PCR and qRT-PCR at six weeks post-germination. qRT-PCR analysis using the ΔΔCT method indicated higher TaNF-YB4 expression in transgenic lines than in the wild-type control plants. Improved agronomic and phenotypic traits were observed with a 6-36% increase in 1000-grain weight in the selected transgenic lines. Root architecture assessments demonstrated enhanced root length, surface area, and projected area in transgenic lines compared with wild-type plants. Additionally, notable variances in total chlorophyll, protein, and sugar content levels were observed between the transgenic lines and control plants, demonstrating statistical significance with a p-value ≤ 0.05. This study indicates that low-level constitutive expression of TaNF-YB4 can enhance wheat yield, presenting a viable strategy for improving wheat productivity.

Potential Growth of Anammox Bacteria under Aerobic Conditions.

Anammox bacteria are obligate anaerobic bacteria that exist widely in nature with sufficient amounts of dissolved oxygen. However, whether anammox bacteria can grow under aerobic conditions remains unclear. In this study, we found that the production of nitrate in the anammox system under aerobic conditions was significantly higher than that under anaerobic conditions without total nitrogen loss. Anammox bacteria can grow by oxidizing nitrite and dehydrogenating hydrazine to produce electrons for carbon fixation. The hydrazine dehydrogenase in anammox bacteria was inhibited under aerobic conditions, and the nitrite oxidoreductase transcription expression of anammox bacteria increased by 2.7 times compared to that under anaerobic conditions, which was the main way for anammox bacteria perform carbon fixation. DNA-stable isotope probing with 13C bicarbonate found the existence of anammox bacteria with 13C isotopes in aerobic cultivation, further proving that anammox bacteria can grow under aerobic condition. More than half of the pathways in glycolysis, the Wood-Ljungdahl pathway, and the tricarboxylic acid cycle were upregulated in anammox bacteria in aerobic condition. Large amounts of bacterioferritins are the important antioxidative enzymes in anammox bacteria in the aerobic environment, which contributes to their stronger oxygen adaptation than other anaerobes. This study expands our understanding of the growth mechanism of anammox bacteria as well as the oxygen adaptation strategies of obligate anaerobic bacteria.

Ablation resistance and high-temperature insulation capacity of TiB2-B4C modified Al-coated carbon fibre/boron phenolic resin ceramizable composites

The inherent susceptibility to oxidation limits the application of carbon fibre/phenolic resin composites (CF/Ph) in the thermal protection of hypersonic vehicle engines. Herein, TiB2-B4C modified Al-coated carbon fibre/boron phenolic resin ceramizable composites were fabricated. The optimal ceramizable composite (T30C10) exhibited excellent ablation resistance and high-temperature insulation capacity at a linear ablation rate and bottom-surface temperature of -0.00768 mm/s and 129.8 °C, respectively. Oxygen consumption and inhibition, carbon fixation, and self-healing effects contributed to the excellent ablation resistance, and the effects of the Al coatings and carbothermal reduction reactions led to excellent high-temperature insulation capacities.

Current regulates electron donors for heterotrophic and autotrophic microorganisms to enhance sulfate reduction in three-dimensional electrode biofilm reactors

The variability in industrial production often generates wastewater with an unstable carbon-to-sulfur ratio, challenging the concurrent removal of sulfate and organic compounds. Three-dimensional biofilm electrode reactor (3D-BER) technology offers a promising solution, compatible with both autotrophic and heterotrophic sulfate reduction. In this study, four up-flow 3D-BERs with gradient current levels were operated for nearly 400 days to treat simulated high-concentration sulfate wastewater. The effects of current intensity, hydraulic retention time (HRT), and influent carbon-to-sulfur ratio on sulfate and organic removal were investigated. The composition and functions of microbial communities were analyzed by metagenomic sequencing. The synergistic mechanism between heterotrophic and autotrophic sulfate reduction was examined by delineating their individual contributions to sulfate removal. Under optimized conditions (HRT 60 h, influent carbon-to-sulfur ratio of 1.7, and current intensity of 50 mA), the highest removal efficiencies for SO42- and COD reached 70.47 % and 85.58 %, respectively. Elevated current intensity increased the abundances of Desulfuromonadaceae, Desulfovibrionaceae and Methanobacteriaceae, while decreasing Anaerolineaceae and Geobacteraceae. Key genes involved in carbon fixation and hydrogen-relied sulfate reduction showed lower abundances at high current levels, whereas genes for direct electron uptake from the electrode were more abundant. Batch experiments demonstrated a synergistic effect between autotrophic and heterotrophic sulfate reduction, most pronounced at 50 mA. Our work successfully regulates electron donors for microbial reduction of high-concentration sulfate in 3D-BERs by manipulating current intensity, providing new insights into the application of bioelectrochemical technology for complex industrial wastewater treatment.

Integrative physiological and transcriptome analysis unravels the mechanism of low nitrogen use efficiency in burley tobacco.

Burley tobacco, a chlorophyll-deficient mutant with impaired nitrogen use efficiency (NUE), generally requires three to five times more nitrogen fertilization than flue-cured tobacco to achieve a comparable yield, which generates serious environmental pollution and negatively affects human health. Therefore, exploring the mechanisms underlying NUE is an effective measure to reduce environmental pollution and an essential direction for burley tobacco plant improvement. Physiological and genetic factors affecting tobacco NUE were identified using two tobacco genotypes with contrasting NUE in hydroponic experiments. Nitrogen use inefficient genotype (TN90) had lower nitrogen uptake and transport efficiencies, reduced leaf and root biomass, lower nitrogen assimilation and photosynthesis capacity, and lower nitrogen remobilization ability than the nitrogen use efficient genotype (K326). Transcriptomic analysis revealed that genes associated with photosynthesis, carbon fixation, and nitrogen metabolism are implicated in NUE. Three nitrate transporter genes in the leaves (NPF2.11, NPF2.13, and NPF3.1) and three nitrate transporter genes (NPF6.3, NRT2.1, and NRT2.4) in roots were down-regulated by nitrogen starvation, all of which showed lower expression in TN90 than in K326. In addition, the protein-protein interaction (PPI) network diagram identified eight key genes (TPIP1, GAPB, HEMB, PGK3, PSBO, PSBP2, PSAG, and GLN2) that may affect NUE. Less advantageous changes in nitrogen uptake, nitrogen assimilation in combination with nitrogen remobilization, and maintenance of photosynthesis in response to nitrogen deficiency led to a lower NUE in TN90. The key genes (TPIP1, GAPB, PGK3, PSBO, PSBP2, PSAG, and GLN2) were associated with improving photosynthesis and nitrogen metabolism in tobacco plants grown under N-deficient conditions.

Bigger genomes provide environment-dependent growth benefits in grasses.

Increasing genome size (GS) has been associated with slower rates of DNA replication and greater cellular nitrogen (N) and phosphorus demands. Despite most plant species having small genomes, the existence of larger GS species suggests that such costs may be negligible or represent benefits under certain conditions. Focussing on the widespread and diverse grass family (Poaceae), we used data on species' climatic niches and growth rates under different environmental conditions to test for growth costs or benefits associated with GS. The influence of photosynthetic pathway, life history and evolutionary history on grass GS was also explored. We found that evolutionary history, photosynthetic pathway and life history all influence the distribution of grass species' GS. Genomes were smaller in annual and C4 species, the latter allowing for small cells necessary for C4 leaf anatomy. We found larger GS were associated with high N availability and, for perennial species, low growth-season temperature. Our findings reveal that GS is a globally important predictor of grass performance dependent on environmental conditions. The benefits for species with larger GS are likely due to associated larger cell sizes, allowing rapid biomass production where soil fertility meets N demands and/or when growth occurs via temperature-independent cell expansion.

Warming reduces trophic diversity in high-latitude food webs.

The physical effects of climate warming have been well documented, but the biological responses are far less well known, especially at the ecosystem level and at large (intercontinental) scales. Global warming over the next century is generally predicted to reduce food web complexity, but this is rarely tested empirically due to the dearth of studies isolating the effects of temperature on complex natural food webs. To overcome this obstacle, we used 'natural experiments' across 14 streams in Iceland and Russia, with natural warming of up to 20°C above the coldest stream in each high-latitude region, where anthropogenic warming is predicted to be especially rapid. Using biomass-weighted stable isotope data, we found that community isotopic divergence (a universal, taxon-free measure of trophic diversity) was consistently lower in warmer streams. We also found a clear shift towards greater assimilation of autochthonous carbon, which was driven by increasing dominance of herbivores but without a concomitant increase in algal stocks. Overall, our results support the prediction that higher temperatures will simplify high-latitude freshwater ecosystems and provide the first mechanistic glimpses of how warming alters energy transfer through food webs at intercontinental scales.