Transcriptomic analysis reveals insights into the responses of Synechocystis sp. PCC 6803 to acidification during cultivation with ammonium salts as a nitrogen source.

Utilizing ammonium in wastewater is a prospective way to reduce costs for bioproduction by photosynthetic organisms. A model cyanobacterium Synechocystis sp. PCC 6803 takes advantage of tolerance to ammonium compared to other microalgae. However, in this study, we report that Synechocystis growth was inhibited when cultured in a medium containing ammonium. This may be due to the pH decreasing below 6 caused by consuming ammonium. Transcriptomic analysis by RNA-seq revealed that the expression of the genes for proteases, chaperones, and antioxidant-scavenging enzymes was induced, but photosynthetic components were repressed. Although these regulations are similar to the previous studies on acidic stress in nitrate-containing culture, the expression of genes such as sigD, slr0042, slr0373, slr0374, and slr1501 was different, indicating that these phenomena are not simply identical to the known responses to acidic stress. The expression of the genes for photosynthesis, gluconeogenesis, and nitrogen assimilation was repressed, and glycolysis and the tricarboxylic acid cycle were induced. Despite the up-regulation of the carbon catabolism and down-regulation of nitrogen assimilation, the 2-oxoglutarate content in the ammonium-grown cells was lower than that in the nitrate-grown cells, and the contents of the major amino acids, such as Glu, Ala, Asp, and Gly were decreased, while the minor amino acids were the same or increased, especially Arg, Lys, Val, and Ile. These results demonstrated that the acidic stress induced by the consumption of ammonium ions differs from the sudden pH drop, and the Synechocystis cell manages amino acid levels to endure carbon limitation under the stress.

Cross-species transcriptomics reveals differential regulation of essential photosynthesis genes in Hirschfeldia incana.

Photosynthesis is the only yield-related trait not yet substantially improved by plant breeding. Previously, we have established Hirschfeldia incana as the model plant for high photosynthetic light-use efficiency (LUE). Now we aim to unravel the genetic basis of this trait in H. incana, potentially contributing to the improvement of photosynthetic LUE in other species. Here, we compare its transcriptomic response to high light with that of Arabidopsis thaliana, Brassica rapa, and Brassica nigra, three fellow Brassicaceae members with lower photosynthetic LUE. We built a high-light, high-uniformity growing environment, in which the plants developed normally without signs of stress. We compared gene expression in contrasting light conditions across species, utilizing a panproteome to identify orthologous proteins. In-depth analysis of three key photosynthetic pathways showed a general trend of lower gene expression under high-light conditions for all four species. However, several photosynthesis-related genes in H. incana break this trend. We observed cases of constitutive higher expression (like antenna protein LHCB8), treatment-dependent differential expression (as for PSBE), and cumulative higher expression through simultaneous expression of multiple gene copies (like LHCA6). Thus, Hirschfeldia incana shows differential regulation of essential photosynthesis genes, with the light-harvesting complex as the first point of deviation. The effect of these expression differences on protein abundance and turnover, and ultimately the high photosynthetic LUE phenotype is relevant for further investigation. Furthermore, this transcriptomic resource of plants fully grown under, rather than briefly exposed to, a very high irradiance, will support the development of highly efficient photosynthesis in crops.

Novel high-throughput oxygen saturation measurements for quantifying the physiological performance of macroalgal early life stages.

Understanding how macroalgal forests will respond to environmental change is critical for predicting future impacts on coastal ecosystems. Although measures of adult macroalgae physiological responses to environmental stress are advancing, measures of early life-stage physiology are rare, in part due to the methodological difficulties associated with their small size. Here we tested a novel, high-throughput method (rate of oxygen consumption and production; V ̇ O 2 $$ \dot{V}{\mathrm{O}}_2 $$ ) via a sensor dish reader microplate system to rapidly measure physiological rates of the early life stages of three habitat-forming macroalgae, the kelp Ecklonia radiata and the fucoids Hormosira banksii and Phyllospora comosa. We measured the rate of O2 consumption (respiration) and O2 production (net primary production) to then calculate gross primary production (GPP) under temperatures representing their natural thermal range. The V ̇ O 2 $$ \dot{V}{\mathrm{O}}_2 $$ microplate system was suitable for rapidly measuring physiological rates over a temperature gradient to establish thermal performance curves for all species. The V ̇ O 2 $$ \dot{V}{\mathrm{O}}_2 $$ microplate system proved efficient for measures of early life stages of macroalgae ranging in size from approximately 50 µm up to 150 mm. This method has the potential for measuring responses of early life stages across a range of environmental factors, species, populations, and developmental stages, vastly increasing the speed, precision, and efficacy of macroalgal physiological measures under future ocean change scenarios.

Response of photosynthetic characteristics and yield of grape to different CO2 concentrations in a greenhouse.

Due to the enclosed environment of greenhouse grape production, the supply of CO2 required for photosynthesis is often insufficient, leading to photosynthetic downregulation and reduced yield. Currently, the optimal CO2 concentration for grape production in greenhouses is unknown, and the precise control of actual CO2 levels remains a challenge. This study aims to investigate the effects of different CO2 concentrations on the photosynthetic characteristics and yield of grapes, to validate the feasibility of a CO2 gas irrigation system, and to identify the optimal CO2 concentration for greenhouse grape production. In this study, a CO2 gas irrigation system combining CO2 enrichment and gas irrigation techniques was used with a 5-year-old Eurasian grape variety (Vitis vinifera L.) 'Flame Seedless.' Four CO2 concentration treatments were applied: 500 ppm (500 ± 30 µmol·mol-1), 700 ppm (700 ± 30 µmol·mol-1), 850 ppm (850 ± 30 µmol·mol-1), and 1,000 ppm (1,000 ± 30 µmol·mol-1). As CO2 concentration increased, chlorophyll a, chlorophyll b, and carotenoids in grape leaves all reached maximum values at 700 ppm and 850 ppm during the same irrigation cycle, while the chlorophyll a/b ratio was lower than at other concentrations. The net photosynthetic rate (Pn) and water use efficiency (WUE) of grape leaves were the highest at 700 ppm. The transpiration rate and stomatal conductance at 700 ppm and 850 ppm were significantly lower than those at other concentrations. The light saturation point and apparent quantum efficiency reached their maximum at 850 ppm, followed by 700 ppm. Additionally, the maximum net photosynthetic rate, carboxylation efficiency, electron transport rate, and activities of SOD, CAT, POD, PPO, and RuBisCO at 700 ppm were significantly higher than at other concentrations, with the highest yield recorded at 14.54 t·hm-2. However, when the CO2 concentration reached 1,000 ppm, both photosynthesis and yield declined to varying degrees. Under the experimental conditions, the optimal CO2 concentration for greenhouse grape production was 700 ppm, with excessive CO2 levels gradually inhibiting photosynthesis and yield. The results provide a theoretical basis for the future application of CO2 fertilization and gas irrigation techniques in controlled greenhouse grape production.

How photosynthetic performance impacts agricultural productivity in hybrid cotton offspring.

Currently, heterosis is an effective method for achieving high crop quality and yield worldwide. Owing to the challenges of breeding and the high cost of the F1 generation, the F2 generation is considered the more desirable hybrid offspring for agricultural production. The use of OJIP fluorescence provides rapid insights into various photosynthetic mechanisms. However, OJIP fluorescence has not been previously studied as an indicator of the rate of heterosis. Consequently, we investigated the relationship between photosynthetic characteristics and growth and developmental parameters in hybrid cotton cultivars. The findings showed a gradual decline in the photosynthetic performance of hybrid cotton as the number of generations increased. In comparison to the F3 generation, both the F1 and F2 generations showed minimal variations in parameters, thus maintaining hybrid dominant and emphasizing the agricultural production potential of the F2 generation. The JIP-test revealed significant differences in the relationship between ψ Eo and ϕ Eo parameters, as well as variations in the connections between the photo-response center and electron transfer efficiency, and between cotton yield and fiber quality in the hybrid progeny. These variations can serve as indicators for predicting the extent of hybrid dominance in cotton. The results indicated significant differences in the light and dark responses of the hybrid offspring. By using parents with similar photosynthetic performance as genetic resources for crossbreeding, the photosynthetic capacity of the hybrid progeny can be enhanced to facilitate the efficient absorption and conversion of light energy in crops.

Development and validation of an oil palm model for a wide range of planting densities and soil textures in Malaysian growing conditions.

A semi-mechanistic oil palm growth and yield model called Sawit.jl was developed to account for a wide range of planting densities and soil textures under Malaysia's climate conditions. The model comprises components related to meteorology, photosynthesis, energy balance, soil water content, and crop growth. The model simulates instantaneous meteorological properties using daily weather data, calculates simultaneous evaporation from crop and soil with the Shuttleworth-Wallace model, determines soil water content through Darcy's law, and adapts a biochemical C3 model for photosynthesis. The model is also parameterized using updated measurements from the newer tenera oil palm, including temperature-dependent Rubisco kinetics, specific leaf area, and the partitioning of nutrients and dry matter between various tree parts. Sawit.jl was validated using historical field measurement data from seven Malaysian oil palm sites, encompassing palm ages spanning 1-23 years. These seven sites differed in soil type (Inceptisols and Ultisols), planting density (82-299 palms ha-1), soil texture (27-59 % clay and 7-67 % sand), and rainfall (1800-2800 mm yr-1). The model showed overall good accuracy in simulating oil palm parameters (except for trunk weight) across diverse conditions, with model agreement metrics ranging from 6 to 27 % for model absolute errors, -22 to +17 % for model bias, and 0.38 to 0.98 for the Kling-Gupta Efficiency index. The model also predicted the response of oil palm yield to abrupt rainfall changes, such as those during El Niño and La Niña events, while accounting for how soil texture, rainfall, and other meteorological factors influence water deficits and crop photosynthesis. However, model accuracy varied by site, planting density, and oil palm parameter. Model accuracy can be increased by more accurately representing the oil palm microclimate, incorporating fruiting activity, and refining the dry matter partitioning mechanism for the trunk.

Chlorophyll fluorescence, physiology, and yield of winter wheat under different irrigation and shade durations during the grain-filling stage.

The uneven spatial and temporal distribution of light resources and water scarcity during the grain-filling stage pose significant challenges for sustainable crop production, particularly in the arid areas of the Loess Plateau in Northwest China. This study aims to investigate the combined effects of drought and shading stress on winter wheat growth and its physio-biochemical and antioxidative responses. Wheat plants were subjected to different drought levels- full irrigation (I100), 75% of full irrigation (I75), 50% of full irrigation (I50), and 25% of full irrigation (I25), and shading treatments - 12, 9, 6, 3 and 0 days (SD12, SD9, SD6, SD3, and CK, respectively) during the grain-filling stage. The effects of drought and shading treatments reduced yield in descending order, with the most significant reductions observed in the SD12 and I25 treatments. These treatments decreased grain yield, spikes per plant, 1000-grain weight, and spikelets per spike by 160.67%, 248.13%, 28.22%, and 179.55%, respectively, compared to the CK. Furthermore, MDA content and antioxidant enzyme activities exhibited an ascending trend with reduced irrigation and longer shading durations. The highest values were recorded in the I75 and SD12 treatments, which increased MDA, SOD, POD, and CAT activities by 65.22, 66.79, 65.07 and 58.38%, respectively, compared to the CK. The Pn, E, Gs, and iCO2 exhibited a decreasing trend (318.14, 521.09, 908.77, and 90.85%) with increasing shading duration and decreasing irrigation amount. Drought and shading treatments damage leaf chlorophyll fluorescence, decreasing yield and related physiological and biochemical attributes.

Intracellular Gold Nanocluster/Organic Semiconductor Heterostructure for Enhancing Photosynthesis.

Photosynthetic microorganisms, which rely on light-driven electron transfer, store solar energy in self-energy carriers and convert it into bioenergy. Although these microorganisms can operate light-induced charge separation with nearly 100% quantum efficiency, their practical applications are inherently limited by the photosynthetic energy conversion efficiency. Artificial semiconductors can induce an electronic response to photoexcitation, providing additional excited electrons for natural photosynthesis to improve solar conversion efficiency. However, challenges remain in importing exogenous electrons across cell membranes. In this work, we have developed an engineered gold nanocluster/organic semiconductor heterostructure (AuNC@OFTF) to couple the intracellular electron transport chain of living cyanobacteria. AuNC@OFTF exhibits a prolonged excited state lifetime and effective charge separation. The internalized AuNC@OFTF permits its photogenerated electrons to participate in the downstream of photosystem II and construct an oriented electronic highway, which enables a five-fold increase in photocurrent in living cyanobacteria. Moreover, the binding events of AuNC@OFTF established an abiotic-biotic electronic interface at the thylakoid membrane to enhance electron flux and finally furnished nicotinamide adenine dinucleotide phosphate. Thus, AuNC@OFTF can be exploited to spatiotemporally manipulate and enhance the solar conversion of living cyanobacteria in cells, providing an extended nanotechnology for re-engineering photosynthetic pathways.

The mechanisms of photoinhibition and repair in plants under high light conditions and interplay with abiotic stressors.

This review comprehensively examines the phenomenon of photoinhibition in plants, focusing mainly on the intricate relationship between photodamage and photosystem II (PSII) repair and the role of PSII extrinsic proteins and protein phosphorylation in these processes. In natural environments, photoinhibition occurs together with a suite of concurrent stress factors, including extreme temperatures, drought and salinization. Photoinhibition, primarily caused by high irradiance, results in a critical imbalance between the rate of PSII photodamage and its repair. Central to this process is the generation of reactive oxygen species (ROS), which not only impair the photosynthetic apparatus first PSII but also play a signalling role in chloroplasts and other cellulular structures. ROS generated under stress conditions inhibit the repair of photodamaged PSII by suppressing D1 protein synthesis and affecting PSII protein phosphorylation. Furthermore, this review considers how environmental stressors exacerbate PSII damage by interfering with PSII repair primarily by reducing de novo protein synthesis. In addition to causing direct damage, these stressors also contribute to ROS production by restricting CO2 fixation, which also reduces the intensity of protein synthesis. This knowledge has significant implications for agricultural practices and crop improvement under stressful conditions.

The phototoxicity of sulfamethoxazole stress on pakchoi cabbage (Brassica rapa var. chinensis) seedlings: From the perspective of photoreaction and omics analysis.

The increasing use of antibiotics has attracted widespread attention to their environmental risks. However, the phototoxicity of sulfonamide antibiotics to plants remain unclear. In this study, the mechanism of the effect of sulfamethoxazole on photosynthesis of pakchoi cabbage (Brassica rapa var. chinensis) was investigated. The results showed that sulfamethoxazole inhibited the growth of pakchoi cabbage and produced photosynthetic toxicity. The growth inhibition rates increased with concentration, the root and shoot weight were 76.02 % and 47.04 % of the control, respectively, with stay-greens phenomenon in 4 mg·L-1 sulfamethoxazole treatment. Chlorophyll precursors (protoporphyrin IX (Proto IX), Mg-proto IX, and protochlorophyllide (Pchlide), 5-aminolevulinic acid (ALA), and porphobilinogen (PBG)) were 1.38-, 1.26-, 1.12-, 1.71-, and 0.96-fold of the control, respectively; photosynthetic pigments (chlorophyll a, chlorophyll b, and carotenoids) were 1.26-, 1.39-, and 1.03-fold of the control, respectively. Respiration rate was 271.42 % of the control, whereas the net photosynthetic rate was 50.50 % of the control. The maximum photochemical quantum yield of PSII (Fv/Fm), the actual photosynthetic efficiency (Y(II)), the quantum yield of non-regulated energy dissipation (Y(NO)), the apparent electron transfer efficiency of PSII (ETR) under actual light intensity were affected, and chloroplast swelling was observed. Proteomic analysis showed that photosynthesis-related pathways were significantly up-regulated, biological processes such as light response, carbohydrates, and reactive oxygen species were activated. Metabolomic analysis revealed that the tricarboxylic acid cycle (TCA cycle) and carbohydrate catabolism were stimulated significantly (p < 0.05), sugars and amino acids were increased to regulate and enhance the resilience of photosynthesis. While folate biosynthesis and ribosomal pathways were significantly down-regulated, the synthesis and translation processes of amino acids and nucleotides were inhibited.

Light-Induced Charge Separation in Photosystem I from Different Biological Species Characterized by Multifrequency Electron Paramagnetic Resonance Spectroscopy.

Photosystem I (PSI) serves as a model system for studying fundamental processes such as electron transfer (ET) and energy conversion, which are not only central to photosynthesis but also have broader implications for bioenergy production and biomimetic device design. In this study, we employed electron paramagnetic resonance (EPR) spectroscopy to investigate key light-induced charge separation steps in PSI isolated from several green algal and cyanobacterial species. Following photoexcitation, rapid sequential ET occurs through either of two quasi-symmetric branches of donor/acceptor cofactors embedded within the protein core, termed the A and B branches. Using high-frequency (130 GHz) time-resolved EPR (TR-EPR) and deuteration techniques to enhance spectral resolution, we observed that at low temperatures prokaryotic PSI exhibits reversible ET in the A branch and irreversible ET in the B branch, while PSI from eukaryotic counterparts displays either reversible ET in both branches or exclusively in the B branch. Furthermore, we observed a notable correlation between low-temperature charge separation to the terminal [4Fe-4S] clusters of PSI, termed FA and FB, as reflected in the measured FA/FB ratio. These findings enhance our understanding of the mechanistic diversity of PSI's ET across different species and underscore the importance of experimental design in resolving these differences. Though further research is necessary to elucidate the underlying mechanisms and the evolutionary significance of these variations in PSI charge separation, this study sets the stage for future investigations into the complex interplay between protein structure, ET pathways, and the environmental adaptations of photosynthetic organisms.

H3K27me3 and EZH Are Involved in the Control of the Heat-Stress-Elicited Morphological Changes in Diatoms.

Marine water temperatures are increasing due to anthropogenic climate change, constituting a major threat to marine ecosystems. Diatoms are major marine primary producers, and as such, they are subjected to marine heat waves and rising ocean temperatures. Additionally, under low tide, diatoms are regularly exposed to high temperatures. However, physiological and epigenetic responses to long-term exposure to heat stress remain largely unknown in the diatom Phaeodactylum tricornutum. In this study, we investigated changes in cell morphology, photosynthesis, and H3K27me3 abundance (an epigenetic mark consisting of the tri-methylation of lysine 27 on histone H3) after moderate and elevated heat stresses. Mutants impaired in PtEZH-the enzyme depositing H3K27me3-presented reduced growth and moderate changes in their PSII quantum capacities. We observed shape changes for the three morphotypes of P. tricornutum (fusiform, oval, and triradiate) in response to heat stress. These changes were found to be under the control of PtEZH. Additionally, both moderate and elevated heat stresses modulated the expression of genes encoding proteins involved in photosynthesis. Finally, heat stress elicited a reduction of genome-wide H3K27me3 levels in the various morphotypes. Hence, we provided direct evidence of epigenetic control of the H3K27me3 mark in the responses of Phaeodactylum tricornutum to heat stress.

Flux Calculation for Primary Metabolism Reveals Changes in Allocation of Nitrogen to Different Amino Acid Families When Photorespiratory Activity Changes.

Photorespiration, caused by oxygenation of the enzyme Rubisco, is considered a wasteful process, because it reduces photosynthetic carbon gain, but it also supplies amino acids and is involved in amelioration of stress. Here, we show that a sudden increase in photorespiratory activity not only reduced carbon acquisition and production of sugars and starch, but also affected diurnal dynamics of amino acids not obviously involved in the process. Flux calculations based on diurnal metabolite profiles suggest that export of proline from leaves increases, while aspartate family members accumulate. An immense increase is observed for turnover in the cyclic reaction of glutamine synthetase/glutamine-oxoglutarate aminotransferase (GS/GOGAT), probably because of increased production of ammonium in photorespiration. The hpr1-1 mutant, defective in peroxisomal hydroxypyruvate reductase, shows substantial alterations in flux, leading to a shift from the oxoglutarate to the aspartate family of amino acids. This is coupled to a massive export of asparagine, which may serve in exchange for serine between shoot and root.

In vivo ElectroChromic Shift measurements of photosynthetic activity in far-red absorbing cyanobacteria.

Some cyanobacteria can do photosynthesis using not only visible but also far-red light that is unused by most other oxygenic photoautotrophs because of its lower energy content. These species have a modified photosynthetic apparatus containing red-shifted pigments. The incorporation of red-shifted pigments decreases the photochemical efficiency of photosystem I and, especially, photosystem II, and it might affect the distribution of excitation energy between the two photosystems with possible consequences on the activity of the entire electron transport chain. To investigate the in vivo effects on photosynthetic activity of these pigment changes, we present here the adaptation of a spectroscopic method, based on a physical phenomenon called ElectroChromic Shift (ECS), to the far-red absorbing cyanobacteria Acaryochloris marina and Chroococcidiopsis thermalis PCC7203. ECS measures the electric field component of the trans-thylakoid proton motive force generated by photosynthetic electron transfer. We show that ECS can be used in these cyanobacteria to investigate in vivo the stoichiometry of photosystem I and photosystem II and their absorption cross-section, as well as the overall efficiency of light energy conversion into electron transport. Our results indicate that both species use visible and far-red light with similar efficiency, despite significant differences in their light absorption characteristics. ECS thus represents a new non-invasive tool to study the performance of naturally occurring far-red photosynthesis.

Integration of Plasmonic Ag(I) Clusters and Fe(II) Porphyrinates into Metal-Organic Frameworks for Efficient Photocatalytic CO2 Reduction Coupling with Photosynthesis of Pure H2O2.

Efficient photocatalytic CO2 reduction coupled with the photosynthesis of pure H2O2 is a challenging and significant task. Herein, using classical CO2 photoreduction site iron porphyrinate as the linker, Ag(I) clusters were spatially separated and evenly distributed within a new metal-organic framework (MOF), namely Ag27TPyP-Fe. With water as electron donors, Ag27TPyP-Fe exhibited remarkable performances in artificial photosynthetic overall reaction with CO yield of 36.5 µmol g-1 h-1 and ca. 100% selectivity, as well as H2O2 evolution rate of 35.9 µmol g-1 h-1. Since H2O2 in the liquid phase can be more readily separated from the gaseous products of CO2 photoreduction, high-purity H2O2 with a concentration up to 0.1 mM was obtained. Confirmed by theoretical calculations and the established energy level diagram, the reductive iron(II) porphyrinates and oxidative Ag(I) clusters within an integrated framework functioned synergistically to achieve artificial photosynthesis. Furthermore, photoluminescence spectroscopy and photoelectrochemical measurements revealed that the robust connection of Ag(I) clusters and iron porphyrinate ligands facilitated efficient charge separation and rapid electron transfer, thereby enhancing the photocatalytic activity.

Path creation as a discursive process: A study of discussion starters in the field of solar fuels.

When a technology is seen as the right solution to a recognized problem, the development of alternative technologies comes under threat. To secure much-needed resources, proponents of alternative technologies must, in these conditions, restart societal discussion on the status quo, a process at once technological and discursive known as 'path creation'. In this article, we investigate discussion-restarting strategies employed by supporters of emerging technologies in the field of solar fuels, particularly the advocates of a technology referred to as 'artificial photosynthesis'. For illustrative purposes we explore four such strategies: revisiting weak spots, resizing the problem, redefining the game, and renegotiating labels. We conclude with a methodological reflection on the empirical study of discursive strategies in a socio-technical system. We further suggest a more systematic application of discourse-analytical and argumentation-theoretical insights that can complement current scholarship on path dependence and path creation.

Short-term hyposalinity stress increases dissolved organic carbon (DOC) release by the macroalga Sargassum fallax (Ochrophyta).

Dissolved organic carbon (DOC) released by macroalgae supports coastal ocean carbon cycling and contributes to the total oceanic DOC pool. Salinity fluctuates substantially in coastal marine environments due to natural and anthropogenic factors, yet there is limited research on how salinity affects DOC release by ecologically important macroalgae. Here we determined the effect of short-term salinity changes on rates of DOC release by the habitat-forming fucalean seaweed Sargassum fallax (Ochrophyta). Lateral branches (~4 g) cut at the axes of mature individuals were incubated across a salinity gradient (4-46) for 24 h under a 12:12 light:dark cycle, and seawater was sampled for DOC at 0, 12, and 24 h. Physiological assays (tissue water content, net photosynthesis, respiration, tissue carbon, and nitrogen content) were undertaken at the end of the 24-h experiment. Dissolved organic carbon release increased with decreasing salinity while net photosynthesis decreased. Dissolved organic carbon release rates at the lowest salinity tested (4) were ~3.3 times greater in the light than in the dark, indicating two potential DOC release mechanisms: light-mediated active exudation and passive release linked to osmotic stress. Tissue water content decreased with increasing salinity. These results demonstrate that hyposalinity stress alters the osmotic status of S. fallax, reducing photosynthesis and increasing DOC release. This has important implications for understanding how salinity conditions encountered by macroalgae may affect their contribution to the coastal ocean carbon cycle.

Alteration of stress-physiological mechanisms in sRNA-treated sweet corn plants during MDMV infection.

Maize dwarf mosaic virus (MDMV) can significantly reduce the growth and development of susceptible varieties of sweet corn. The virus utilises the energy and reserve sources of plant cells to ensure its reproduction in the microspaces formed by cell membranes. Therefore, the severity of stress can be monitored by examining certain physiological changes, for example, changes in the degree of membrane damage caused by lipid peroxidation, as well as changes in the amount of photosynthetic pigments. The activation of antioxidant enzymes (e.g. ascorbate peroxidase, guaiacol peroxidase, glutathione reductase) and the accumulation of phenolic compounds with antioxidant properties can indirectly protect against the oxidative stress caused by the presence of the positive orientation, single-stranded RNA-virus. This study demonstrates the changes in these physiological processes in a sweet corn hybrid (Zea mays cv. saccharata var. Honey Koern.) susceptible to MDMV infection, and suggests that exogenous small RNA treatment can mitigate the damage caused by virus infection.

RNA-seq reveals the gene expression in patterns in Populus × euramericana 'Neva' plantation under different precision water and fertilizer-intensive management.

BACKGROUND: Populus spp. is a crucial fast-growing and productive tree species extensively cultivated in the mid-latitude plains of the world. However, the impact of intensive cultivation management on gene expression in plantation remains largely unexplored. RESULTS: Precision water and fertilizer-intensive management substantially increased key enzyme activities of nitrogen transport, assimilation, and photosynthesis (1.12-2.63 times than CK) in Populus × euramericana 'Neva' plantation. Meanwhile, this management approach had a significant regulatory effect on the gene expression of poplar plantations. 1554 differential expression genes (DEGs)were identified in drip irrigation (ND) compared with conventional irrigation. Relative to ND, 2761-4116 DEGs, predominantly up-regulated, were identified under three drip fertilization combinations, among which 202 DEGs were mainly regulated by fertilization. Moreover, drip irrigation reduced the expression of cell wall synthesis-related genes to reduce unnecessary water transport. Precision drip and fertilizer-intensive management promotes the synergistic regulation of carbon and nitrogen metabolism and up-regulates the expression of major genes in nitrogen transport and assimilation processes (5 DEGs), photosynthesis (15 DEGs), and plant hormone signal transduction (11 DEGs). The incorporation of trace elements further enhanced the up-regulation of secondary metabolic process genes. In addition, the co-expression network identified nine hub genes regulated by precision water and fertilizer-intensive management, suggesting a pivotal role in regulating the growth of poplar. CONCLUSION: Precision water and fertilizer-intensive management demonstrated the ability to regulate the expression of key genes and transcription factor genes involved in carbon and nitrogen metabolism pathways, plant hormone signal transduction, and enhance the activity of key enzymes involved in related processes. This regulation facilitated nitrogen absorption and utilization, and photosynthetic abilities such as light capture, light transport, and electron transport, which faintly synergistically regulate the growth of poplar plantations. These results provide a reference for proposing highly efficient precision intensive management to optimize the expression of target genes.

Physcomitrium patens flavodiiron proteins form heterotetrametric complexes.

Flavodiiron proteins (FLVs) catalyze the reduction of oxygen to water by using electrons from Photosystem I (PSI). In several photosynthetic organisms such as cyanobacteria, green algae, mosses and gymnosperms, FLV-dependent electron flow protects PSI from over-reduction and consequent damage especially under fluctuating light conditions. In this work we investigated biochemical and structural properties of FLVA and FLVB from the model moss Physcomitrium patens. The two proteins, expressed and purified from Escherichia coli, bind both iron and flavin cofactors and show NAD(P)H oxidase activity as well as oxygen reductase capacities. Moreover, the co-expression of both FLVA and FLVB, coupled to a tandem affinity purification procedure with two different affinity tags, enabled the isolation of the stable and catalytically active FLVA/B hetero tetrameric protein complex with cooperative nature. The multimeric organization was shown to be stabilized by inter-subunit disulfide bonds. This investigation provides valuable new information on the biochemical properties of FLVs, with new insights into their in vivo activity.