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In response to rising CO2 emissions driving global warming, there is an urgent need for a transition toward a sustainable bioeconomy. Photo-biotechnological processes based on oxygenic photosynthesis hold high potential for achieving CO2 neutrality and in this regard, cyanobacteria have emerged as promising biocatalysts. Rational metabolic engineering of cyanobacteria depends on a thorough understanding of regulatory mechanisms governing primary metabolism, because native metabolic flux through specific pathways and, consequently, the formation of target products can be limited. Recent insights have identified a key regulatory node at the 2,3-bisphosphogylcerate-independent phosphoglycerate mutase (PGAM) reaction, where the metabolic flux from newly fixed carbon is redirected from the Calvin-Benson-Bassham (CBB) cycle towards lower glycolysis. This metabolic valve is controlled by the small inhibitor protein PirC, whose binding to PGAM is determined by the central signal transduction protein PII. In this study, we exploit the PirC-PGAM interaction as a novel target for regulatory metabolic engineering in the model cyanobacterium Synechocystis sp. PCC 6803 (Synechocystis). Chassis strains with engineered control of PGAM, defined as PGAM-ON or PGAM-OFF states, were generated using two complementary approaches: tuning pgam gene expression and modulating PirC abundance to regulate PGAM activity. The effectiveness of this regulatory engineering strategy was demonstrated by redirecting carbon flux toward two representative, naturally occurring products: sucrose, produced via gluconeogenesis fueled by the Calvin-Benson-Bassham (CBB) cycle, and succinate, an intermediate of the tricarboxylic acid (TCA) cycle. Narrowing the PGAM valve resulted in a threefold increase in sucrose accumulation. In contrast, opening the PGAM valve by relieving PGAM inhibition through pirC deletion or separate pgam overexpression resulted in up to an 18-fold increase in succinate excretion. Furthermore, similar genetic configurations were applied to enhance production of a heterologous compound, isoprene, derived from pyruvate. This study establishes the PGAM valve as a tunable control point for the rational re-direction of carbon flux in Synechocystis and highlights small regulatory proteins as powerful targets for metabolic engineering. Together, these findings provide proof of concept for an advanced level of molecular engineering in cyanobacteria and to fully harness their biocatalytic potential in future photosynthesis-driven biotechnological applications.

Strigolactones mitigate Cr(VI) toxicity in Capsicum annuum by limiting chromium uptake and reprogramming photosynthesis and redox metabolism, thereby preserving chloroplast function and cellular integrity. Agricultural soil contamination and its impact on the crops require alternative strategies to reduce associated environmental risks. Strigolactones (SLs) are emerging phytohormones that regulate plant development and stress adaptation; however, their role in hexavalent chromium [Cr(VI)] tolerance remains poorly understood. Here, we investigated the mechanistic basis of SL-mediated mitigation of Cr(VI) toxicity in Capsicum annuum using the synthetic analog rac-GR24. Cr(VI) stress severely impaired photosynthetic performance by disrupting photosystem efficiency, suppressing Calvin-Benson cycle enzyme activities, and reducing ATP and NADPH production, leading to excessive reactive oxygen species accumulation and cellular damage. rac-GR24 markedly decreased Cr uptake and restored photosynthetic carbon metabolism by enhancing the expression of key Calvin cycle enzymes and genes such as RbcS, RbcL, PGK, GAPDH, and PRK. The regulation of fluorescence parameters such as Fv/Fm, ФPSII, and ETR improved PSI and PSII functioning, and rebalanced the adenylate and pyridine nucleotide pools. GR24 reinforced redox homeostasis by activating antioxidant defence, stimulating the ascorbate-glutathione and glyoxalase pathways, resulting in reduced lipid peroxidation and improved cell viability. Ultrastructural observations confirmed improved chloroplast integrity and stomatal behavior under SL treatment. The enhancement of photosynthesis and reduction of stress-related biomarkers are probably the consequences of decreased Cr accumulation in roots and shoots upon rac-GR24 treatment, as indicated by the differential expression of SULTR1.2, SULTR1.3, and SULTR3 genes. These findings demonstrate that GR24 could be highly effective in alleviating Cr-induced toxicity in C. annuum. This protective effect is mediated through the coordinated regulation of photosynthetic carbon metabolism and antioxidant defense system, leading to redox regulation, protection of chloroplasts, and better photosynthetic performance.

Chemoautotrophs drive carbon fixation in coastal sediments, but most of them remain uncultured with poorly characterized in situ activities. In this study, a cultivation-independent single-cell approach combining Raman spectroscopy with 13C-stable isotope probing was developed to enable direct identification of active chemoautotrophs in coastal sediments using function-specific spectral biomarkers, targeted metagenomic sequencing and pure culture verification. 13C-induced shifts in cytochrome c (749, 1129, 1312, 1589 cm-1) and phenylalanine (1002 cm-1) Raman bands were systematically evaluated and applied as functional biomarkers through investigations of both representative chemoautotrophic strains and environmental samples. The combined analysis of targeted sorting of active chemoautotrophic cells and metagenomic sequencing revealed dominant species and a complete Calvin-Benson-Bassham (CBB) cycle pathway in sulfur-oxidizing guilds. Remarkably, a novel sulfur-oxidizing chemoautotroph, Guyparkeria sp. TX1, which showed ≥99% gene sequence similarity to contigs recovered from sorted-cell metagenomes, was isolated from enrichment cultures. Its significant carbon fixation capacity provided experimental validation for the effectiveness of Raman-based in situ functional screening. This study establishes Raman-based functional biomarkers applicable to chemoautotrophic carbon fixation, enabling in situ mapping of microbial carbon fluxes. By integrating single-cell phenotypic activity with genomic potential, this work advances the mechanistic understanding of sulfur-driven dark carbon fixation, which sustains coastal blue carbon ecosystems as a keystone process.

Genomic resources for thermophilic cyanobacteria remain limited, hindering understanding of their ecology and adaptations to extreme high-temperature environments. This study characterizes the genomic features of thermophilic cyanobacteria from thermal springs, focusing on their strategies to cope with energy limitations and the genetic basis of secondary metabolite production. We analyzed six newly assembled genomes, and compared them with reference genomes from thermophilic and mesophilic cyanobacteria. Functional gene analysis, genome size comparisons, and biosynthetic gene cluster (BGC) mining were performed to assess adaptations. Genome sizes varied substantially, with Hillbrichtia pamiria showing a notably reduced genome, whereas Calothrix thermalis and Thermoleptolyngbya hindakii were similar to or larger than related mesophiles. Secondary metabolite BGCs were generally reduced in thermophiles, especially in H. pamiria, although larger genomes retained diverse BGCs, including cyanotoxins, nonribosomal peptide synthetases (NRPS), ribosomally synthesized and post-translationally modified peptides (RiPPs) and terpenes. Core functions, the Calvin cycle and nitrogen fixation, were conserved, while lineage-specific variation occurred in Tricarboxylic Acid (TCA) cycle, sulfur assimilation, and denitrification genes. Amphirytos necridicus harbors features suggesting adaptation to low-energy environments, like alternative TCA cycle enzymes. These findings expand the genomic and functional landscape of thermophilic cyanobacteria, reveal lineage-specific adaptations, and underscore the value of learning from these natural strategies for potential biotechnological applications.

Disulfide bonds act as reversible switches that regulate cellular function in nearly all organisms. Their behavior is set by the midpoint potential (Em), yet Em is known for only a small number of sites, mostly in purified proteins studied away from their natural partners. We developed a mass-spectrometry workflow that measures Em directly from native cell lysates. By equilibrating proteins of the cyanobacterium Synechocystis sp. PCC 6803 in defined redox buffers and reading out the oxidation state of individual cysteines, we obtained 368 Em values across the proteome and validated them against purified proteins. A key example is the regulatory protein CP12: its Em in isolation differs strongly from the value measured in lysate and converges only when its physiological partner, thioredoxin, is included, showing that our approach captures the effective potentials that operate inside cells. Combining Em with absolute measurements of cysteine redox state in light and darkness, we mapped intracellular redox "operating points" for Calvin-Benson-Bassham (CBB) cycle enzymes. Phosphoribulokinase sits near thioredoxin, whereas fructose 1,6-bisphosphatase/sedoheptulose 1,7-bisphosphatase (F/SBPase) and CP12 are maintained at more oxidized, nonequilibrium states. These results reveal a hierarchical redox control network in photosynthetic metabolism and provide a general strategy for measuring context-dependent redox switches in living systems.

King grass is a fast-growing C4 perennial with high biomass potential, yet its productivity is limited by cold stress. WRKY transcription factors (TFs) regulate abiotic stress responses, but their roles in king grass cold adaptation remain unclear. WRKY TFs were identified genome-wide using BLASTP and HMMER, followed by phylogenetic classification, transcriptome profiling, promoter cis-element analysis, weighted gene co-expression network analysis (WGCNA), molecular docking, and yeast heterologous expression assays. Sixty-two PsiWRKY genes were identified and classified into three groups. Time-series transcriptome analysis across nine cold-stress time points revealed four expression patterns, with 29 genes significantly induced (> 2-fold), mainly during late acclimation (48-72 h). qRT-PCR confirmed RNA-seq trends (R² = 0.742). Functional enrichment and WGCNA analyses indicated that cold-responsive PsiWRKYs coordinate abscisic acid-gibberellin antagonism and sugar metabolism. Molecular docking predicted interactions between PsiWRKY proteins and Calvin cycle enzymes, with PsiWRKY16 and PsiWRKY55 showing the highest structural confidence (pTM > 0.75). Network analysis identified PsiWRKY16 and PsiWRKY50 as hub regulators linking GA signaling genes (GID1/DELLA) with sugar metabolism enzymes such as GAPDH and PRK. Yeast assays quantitatively confirmed enhanced cold tolerance, as heterologous expression of PsiWRKY16 reduced doubling time by 0.56 h and increased area under the curve and carrying capacity by 26.20 and 3.39, respectively, while PsiWRKY50 increased these values by 14.45 and 1.43. Promoter analysis showed enrichment of ABRE and DRE elements (p = 0.00061), and integrative target prediction identified 193 genes co-regulated by WRKY and CBF pathways, supporting ABA-CBF signaling convergence. PsiWRKYs exhibit subgroup-specific and time-resolved responses to cold stress. PsiWRKY16, PsiWRKY50, and PsiWRKY55 are implicated in coordinating hormonal signaling and metabolic reprogramming, providing candidate targets for cold-tolerant breeding in king grass.

Cupriavidus necator strain H16 has emerged as a versatile microbial chassis for sustainable bioproduction due to its metabolic flexibility, enabling growth on a wide range of substrates, including H2/CO2, formate, and organic carbon (waste) sources such as volatile fatty acids. This review first provides a comprehensive overview of recent advances in systems-level understanding and metabolic engineering of C. necator. We next discuss recent advances in omics analyses and genome-scale metabolic modeling that are increasingly used to understand the large genome and wide metabolic portfolio of C. necator. We further discuss the native metabolic network, including autotrophic growth via the Calvin Benson Bassham (CBB) cycle, as well as heterotrophic and mixotrophic capabilities. Engineering strategies to enhance substrate utilization and conversion efficiency particularly for H2/CO2, formate, and mixed feedstocks are discussed alongside efforts to expand the substrate range in this organism. Other than the already industrialized production of the bioplastic polyhydroxybutyrate (PHB) and related polyhydroxyalkanoates in C. necator, we provide an overview of the wide range of products for which proof-of-principles have been shown in C. necator. We also discuss recent advances in bioprocess design for gas fermentation, electromicrobial production, and H2-based biocatalytic reduction using C. necator. Finally, we compare C. necator with other hydrogen and formate-utilizing bacteria to identify key knowledge gaps and outline future directions for advancing C. necator as a host for sustainable industrial biotechnology.

Glycine betaine (GB) not only plays an important role as an osmotic regulator in the regulation of abiotic stress in plants, but also serves as a methyl donor that affects the methylation level of the plant, which in turn affects its growth, development and response to adversity. Tomato as a major crop cultivated in facilities, facility soil salinization has become an important factor limiting efficient and high qualities tomato production. In contrast, little has been reported on the effect of GB on m6A methylation and its salt tolerance in tomato. In this study, the effects of exogenous GB on chlorophyll synthesis, photosynthesis and m6A methyltransferase in tomato under salt stress were investigated using tomato as experimental material. The results showed that 5 mM GB pretreatment alleviated the inhibitory effect of salt stress on the growth of tomato plants. GB promotes the synthesis and accumulation of Proto IX, Mg-Proto IX and protochlorophyllide in the chlorophyll synthesis pathway under salt stress by protecting the activities of CHLH (Magnesium-binding enzyme H subunit) and POR (protochlorophyllide oxidoreductase) thereby increasing the chlorophyll content. In addition, GB improves photosynthetic capacity of tomato by increasing stomatal opening and protecting Calvin cycle enzyme activity. And GB altered the expression level of m6A methyltransferase, which in turn indirectly affected the salt tolerance of tomato. In summary, GB may enhance tomato salt tolerance by promoting chlorophyll synthesis, enhancing photosynthesis, and regulating the expression levels of m6A methyltransferase genes. These findings suggest that exogenous GB application could serve as an effective strategy to improve tomato productivity in salinized protected cultivation systems.

Condensed sulphur phases (e.g., S0) are key intermediates in the microbial oxidation of reduced sulphur compounds and influence sulphur cycling in natural systems. Biogenic S0, particularly, extracellular sulphur globules, can serve as an energy substrate for diverse microorganisms and interface with other biogeochemical cycles. However, the cellular processes that generate extracellular globules remain incompletely resolved. Here, using cryogenic electron tomography, scanning transmission electron microscopy and stage-resolved transcriptomics, we tracked sulphur globule formation in Halorhodospira halophila, a purple sulphur bacterium known to produce extracellular sulphur globules. We observed S0 globule nucleation within cells followed by the appearance of globules outside the cell, consistent with export from an intracellular site. Stage-resolved differential gene-expression analyses revealed the upregulation of genes associated with outer membrane remodelling and outer membrane vesicle (OMV) biogenesis during stages in which export is observed, providing indirect support for an OMV-associated export process. Coordinated transcriptional increases in sulphide-oxidation pathways, OMV-related functions, secretion systems, photosynthetic complexes and the Calvin-Benson-Bassham (CBB) cycle suggest integrated metabolic regulation linking sulphide oxidation, photosynthetic energy conservation and carbon fixation to membrane/vesicle production. Together, these observations support a model in which intracellular sulphur metabolism is linked to extracellular S0 reservoirs through an export process potentially involving OMVs.

Chemolithoautotrophic bacteria represent a diverse group of microorganisms capable of utilising carbon dioxide (CO2) as their sole carbon source, deriving the necessary energy for growth and metabolism from redox reactions involving inorganic compounds such as hydrogen, sulfur, or iron. These organisms have attracted substantial scientific and industrial interest due to their dual potential to function as biological CO2 sinks, mitigating greenhouse gas accumulation, and as microbial platforms for the sustainable biosynthesis of value-added compounds. Their natural CO2 fixation pathways, including the Calvin-Benson-Bassham cycle, the reductive tricarboxylic acid cycle, the Wood-Ljungdahl pathway, 3-hydroxypropionate bi-cycle, and reductive glycine pathway constitute the biological foundation for carbon assimilation in these organisms. However, these native pathways often exhibit limited efficiency, constraining their broader application. This comprehensive review discusses recent advances and opportunities in the optimization and redesign of CO2 fixation networks in chemolithoautotrophic bacteria. It extends to the design and development of novel, energy-efficient routes for CO2 fixation, which hold significant potential for large-scale implementation aimed at mitigating greenhouse gas emissions. In addition, the review assesses energy generation and utilization within carbon fixation networks, as well as emerging strategies for optimizing energy and redox balance in metabolic pathways. Finally, it highlights the emerging frontier of developing chemolithoautotrophic bacteria as microbial cell factories, capable of coupling carbon capture with sustainable biomanufacturing, thereby positioning these organisms at the forefront of next-generation climate and bioengineering solutions.

Thermus species are widely recognized as a key group of heterotrophic denitrifiers mediating carbon, nitrogen, and sulfur cycling in geothermal habitats, and have attracted extensive research attention for their thermostable enzyme resources. However, their autotrophic denitrification potential remains poorly characterized, and the systems-level mechanisms underlying their thermal adaptation remain incompletely understood. This study presents three high-quality metagenome-assembled genomes (MAGs) of Thermus from autotrophic sulfur-based denitrification bioreactors. These MAGs encode the complete genetic potential for the Calvin-Benson-Bassham cycle, reductive tricarboxylic acid cycle, and 3-hydroxypropionate bicycle for inorganic carbon fixation. Thermus strains employ a distinct sulfide oxidation route: HS- is first oxidized to polysulfides or glutathione persulfide by fccAB, then condensed with sulfite to form thiosulfate via rhodanese, and finally completely oxidized to sulfate by complete sox cluster. T. scotoductus (MAG1) carries genes for nitrate reduction (narGHI) and dissimilatory nitrate reduction to ammonium (nrfA and nrfH). As conspecific strains, MAG2 and MAG3 harbor abundant denitrification genes (nar, nirK, norBC), indicating strong substrate-driven metabolic plasticity. A protein-protein interaction network further elucidated the systems-level thermoadaptive survival mechanisms of T. scotoductus, identifying chaperone-mediated protein homeostasis and DNA repair-dependent genomic stability as core adaptive strategies, alongside orphan nodes (e.g., aceE, lpd, nuoC) with potential independent functions. Collectively, these findings advance our understanding of Thermus' metabolic plasticity, offer valuable thermostable resources for high-temperature wastewater treatment and industrial applications, and bridge critical knowledge gaps in the autotrophic metabolism and thermoadaptive regulation of thermophilic bacteria-laying a robust genomic foundation for the development and optimization of high-temperature biotechnological processes.

Perfluorohexane sulfonate (PFHxS), a widely used alternative to perfluorooctane sulfonate (PFOS), has been prevalent in aquatic environments. However, its toxic mechanisms in algae remain poorly understood. In this study, a 12-day exposure experiment was conducted to systematically investigate the toxicity of PFHxS in Chlorella pyrenoidosa through physiological parameter measurements and transcriptomic analysis. The results revealed that significant growth inhibition (9%) was observed at 1 mg/L PFHxS on day 12, accompanied by altered photosynthetic responses, including decreases in chlorophyll a and carotenoid contents by 11% and 15%, respectively, at the late exposure stage. On day 12, the accumulation of reactive oxygen species (ROS) triggered a compensatory upregulation of antioxidant enzyme activities, with superoxide dismutase (SOD) and catalase (CAT) increasing by 74% and 79%, respectively. This response was insufficient to prevent severe oxidative stress, which resulted in lipid peroxidation and substantial impairment of energy metabolism, marked by a 57% decline in adenosine triphosphate (ATP) and a 55% decline in reduced nicotinamide adenine dinucleotide phosphate (NADPH). Transcriptomic profiling suggested that PFHxS exposure was associated with suppression of the Calvin cycle and glycolysis while inhibiting the tricarboxylic acid (TCA) cycle and oxidative phosphorylation, thereby impairing energy synthesis. Although C. pyrenoidosa appeared to modulate energy metabolism and exhibited transcriptional changes associated with reduced glycogen turnover and altered fatty acid metabolism, severe oxidative damage coupled with impaired energy metabolism ultimately led to metabolic disturbance. This study provides evidence relevant to evaluating the ecological risks of PFHxS to aquatic systems and provides critical evidence for assessing the environmental impacts of PFHxS.

Sustainable biomanufacturing in Escherichia coli is advancing through the integration of carbon dioxide (CO2)-fixing modules from algal systems. However, the assimilation efficiency remains limited by ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) performance and intracellular CO2 availability. To address these constraints, we introduced carbonic anhydrases from Cyanobacteria aponinum (capoCAs) and repressed the native CA (can) gene using Clustered Regularly Interspaced Short Palindromic Repeats interference (CRISPRi) to enhance design specificity. Afterward, capoCAs were overexpressed in E. coli BL21(DE3) and its derivative strains of can deficient (dCA), Calvin-Benson-Bassham (CBB) (RuBisCO-Prk expressing), and dCA+CBB (coupled with dCA and CBB). For functional demonstration, the engineered strains were used to produce a valuable prodrug, 5-aminolevulinic acid (5-ALA). As a result, capoCAs modestly improved 5-ALA titers, with further increments upon CBB coexpression. The optimum dCA+CBB* strain achieved 7.04 g/l (1.46-fold improvement), alongside 9.59% carbon enrichment and a 39.4% reduction in CO2 release. The 13C-isotope confirmed CO2 incorporation during 5-ALA biosynthesis. This work provides tunable carbon-management modules for developing low-footprint microbial cell factories.

Semi-arid tropical soils inherently contain low soil organic carbon (SOC) and limited nutrient reserves, resulting in poor productivity. Intensive cropping with synthetic fertilizers, further deteriorate soil quality and impair ecosystem functioning. In contrast, organic amendments alone or combined with synthetic fertilizers sustain soil biodiversity through microbially mediated processes. However, how long-term nutrient management shapes soil microbiomes and their functional diversity in semi-arid tropical systems remains largely unknown. To address this gap, we investigated a 116-year-old long-term nutrient management experiment using a multi-omic framework. Shotgun metagenomics characterized the total microbiome (bacteria, archaea, and eukaryota) and associated carbon- and nitrogen-cycling genes under four contrasting nutrient management practices: unfertilized control, inorganic fertilizer alone (IC), organic amendment alone (OM), and integrated nutrient management combining organic and inorganic inputs (INM). OM and INM significantly improved soil nutrient stocks, SOC, microbial biomass, and enzyme activities compared with IC and Control. These treatments also enhanced microbial diversity and shifted communities toward copiotrophic and functionally beneficial taxa, whereas IC and Control were dominated by stress-tolerant oligotrophs. Pathway analysis showed that carbon fixation dominated the C-cycling gene pool, with alternative autotrophic pathways prevailing over the Calvin cycle, particularly under OM and INM. These treatments also supported higher abundances of methanogenic and decomposition-associated genes, indicating enhanced carbon turnover. Nitrogen-cycling functions exhibited pathway-specific responses: OM enriched N-fixation and assimilatory nitrate reduction genes, whereas INM enhanced denitrification and dissimilatory nitrate reduction pathways. IC showed increased nitrification potential but the weakest biologically regulated N pathways. Volatomics profiling showed that OM and INM produced more diverse and metabolically active volatile organic compounds that were strongly associated with SOC and key biological attributes. Collectively, our study underscores the importance of carbon-rich organic inputs in rebuilding soil carbon stocks, reinforcing biological processes, and enhancing nutrient cycling for long-term sustainability of agriculture in semi-arid tropical regions.

Microbial carbon fixation is central to carbon cycling and carbon sink functioning in coastal aquatic ecosystems. Although carbon fixation pathways have been increasingly investigated across diverse aquatic environments, comparative evidence remains limited for hydrologically connected yet hydrochemically contrasting coastal groundwater and surface water systems. This study aimed to compare carbon-fixation-associated microbial communities and major carbon fixation pathways across groundwater, river water, and reservoir water in the Tianjin coastal region. We integrated metagenomic sequencing with hydrochemical analyses to characterize carbon-fixation-associated microbial communities and six representative carbon fixation pathways. Surface waters were dominated by bacteria and showed relatively stable community composition, whereas groundwater communities comprised both bacteria and archaea and displayed pronounced spatial heterogeneity. The Calvin-Benson-Bassham cycle was prevalent across all water types, and the reductive tricarboxylic acid (rTCA) cycle was also widely distributed. Groundwater showed higher contributions of the Wood-Ljungdahl pathway, the archaeal 3-hydroxypropionate/4-hydroxybutyrate and dicarboxylate/4-hydroxybutyrate cycles, together with the rTCA cycle, indicating coexisting carbon fixation strategies. Pathway abundance and module completeness further suggested differences in pathway integrity among water types. Total dissolved solids, HCO3⁻, CO32⁻, and dissolved organic carbon were key correlates of carbon fixation gene distribution. Carbon-fixation-associated microbial communities, pathway distributions, and pathway integrity differed markedly between coastal groundwater and surface waters. Groundwater exhibited enhanced non-CBB cycle potentials and more diversified carbon fixation strategies, highlighting the importance of groundwater processes in evaluating carbon sequestration potential and carbon cycling in hydrochemically heterogeneous coastal aquatic systems.

Adaptive behavior under threat requires balancing reward pursuit against the risk of harm. During approach-avoidance conflict, animals often pause at decision points, but whether these pauses reflect a unified process or distinct decision states remains unclear. Here, we replicate and extend findings from Calvin et al.1 by analyzing hippocampal activity in rats performing a predator-based foraging task across two cohorts. We compared three behaviors: mid-track aborts (MTAs), mid-track continues (MTCs), and attack-triggered retreats. Behaviorally, MTAs and MTCs emerged from a shared pause state but led to different outcomes, whereas retreats reflected rapid, reactive escape following attack. Despite similar behavioral endpoints (return to safety), retreats and MTAs differed markedly in movement dynamics and neural activity. During retreats, hippocampal representations remained biased toward the attack location, consistent with ongoing encoding of immediate threat. In contrast, MTAs showed a shift in representation toward safe locations following the decision to abort. During pauses, hippocampal activity differentiated future behavioral outcomes before movement diverged: pauses preceding MTAs showed stronger representation of threat-related locations, whereas pauses preceding MTCs emphasized goal-related locations. These representational biases were already present during the outbound approach, indicating that decision-related processes emerged at the beginning of the outbound journey. Across experience, representations of threat and goal locations became increasingly differentiated when encountering an attacking robot, diminished during extinction, and re-emerged when the attack was introduced again. Together, these findings extend prior work by dissociating hippocampal representations associated with reactive escape from those underlying anticipatory, anxiety-like decision-making, suggesting that the hippocampus dynamically tracks behaviorally relevant features to guide decisions under threat.

Phytoplasma-mediated witches' broom disease (WBD) causes abnormal growth and inhibits fruit formation in sour jujube trees, causing significant economic damage. Research on the pathogenic mechanisms of WBD and the disease resistance mechanisms of sour jujube tree remains poorly understood. In this study, these mechanisms were investigated using healthy resistant jujube branches that had been grafted onto WBD-infected trees and grown for seven years. Leaves were collected from both healthy resistant branches (KB) and WBD-affected branches (ZFB) to analyze differences in plant physiological indicators, carbon metabolic processes, and transcriptional and protein regulatory mechanisms. The results indicated that, compared with the ZFB group, the KB group had significantly greater levels of photosynthetic indicators, including the transpiration rate, net photosynthetic rate, stomatal conductance, and photosynthetically active radiation. Nutrient absorption and metabolic indicators, such as soluble proteins, were also higher in KB than in ZFB, whereas soluble sugar and starch concentrations were lower. Carbon metabolism profiling revealed that the KB group showed increased fatty acid synthesis for sustained energy production, whereas the ZFB group presented disrupted central carbon flux through an impaired TCA cycle, glycolysis, and pentose phosphate pathways. In addition, ferredoxin (Fd) was identified as a key resistance determinant in jujube trees against WBD phytoplasma. Genes and proteins associated with the photosynthesis pathway exhibited elevated expression levels in KB leaves, particularly those encoding Fd. High Fd expression enhances NADPH and ATP production, accelerates the Calvin cycle, and promotes carbohydrate synthesis. This enhancement supports various biological pathways, including the assimilation of carbon and nitrogen, chlorophyll metabolism, and the synthesis of photosynthetic pigments and fatty acids. In summary, our study reveals that an intact photosynthetic system and its associated metabolism protect resistant branches against WBD, providing a theoretical basis for breeding resistant cultivars.

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Mangrove wetlands are a core component of blue carbon ecosystems worldwide. Elevated suspended particulate matter (SPM) in natural waters is a ubiquitous environmental stressor, yet its effects on the carbon cycling of mangroves remain poorly unelucidated. Here, we conducted a 90-day microcosm experiment using Kandelia obovata and integrated high-resolution chemical and biological profiling to systematically elucidate how SPM loading affects mangrove carbon-cycling processes. As SPM increased from 0 to 30 mg/L, the photosynthetic activity of phytoplankton declined, accompanied by suppressed Calvin-Benson-Bassham-cycle signatures and a relative enrichment of glycolysis- and TCA-related signatures, resulting in a 0.71 mg/L increase in dissolved inorganic carbon (DIC) and a 1.12 mg/L decrease in dissolved organic carbon (DOC) on day 90. Concurrently, suppressed sediment β-glucosidase activity contributed to a 1.76 mg/g increase in sediment organic carbon (SOC). As SPM further increased from 30 to 70 mg/L, strengthened autotrophic carbon fixation and attenuated heterotrophic carbon oxidation in the water column contributed to a 2.45 mg/L decrease in DIC and a 0.30 mg/L increase in DOC. Excessive SPM load compromised the antioxidant defence system of mangroves, leading to oxidative damage in mangrove plants, thereby reducing photosynthetic activity, while sediment β-glucosidase activity increased, collectively resulted in a 1.20 mg/g decrease in SOC. Our results indicate that elevated SPM reorganises carbon composition within mangrove wetlands, with potential implications for global-scale carbon cycling, underscoring the importance of incorporating SPM as a key agent forcing in the management of blue carbon ecosystems.