Photorespiration Research Articles

Integrated response of crop yields and greenhouse gas emissions to cropland management practices and natural factors: A global meta-analysis

Abstract The effects of cropland management on yield and greenhouse gas (GHG) emissions vary among crops, and comprehensive and quantitative analyses of relevant factors are needed to make informed management decisions. The study assessed the response of global crop yields and GHG to cropland management and natural factors (including mean annual temperature (MAT), mean annual rainfall (MAP), soil pH (SPH), soil C N ratio (SCN), soil organic matter (SOC), crop type, biochar (application rate Brate, biochar feedstock Feedstock, C N ratio BCN, biochar pH BPH, biochar organic matter BTC), irrigation, N fertilizer (Nrate), tillage, straw management, plastic film mulch, duration of experiment, economic development, geographic location (state, country)) involving 167 papers from 17 crops in 27 countries, with a total of 1249 pairs of observations by using meta-analysis. The results showed that biochar application throughout the year improved crop yields, reduced GHG and was more suitable for use on C4 crops. The contribution of straw return to CH4 and CO2 was 78.3% and 35.6%, respectively. The effect of intermittent irrigation on the yield of C4 crop was 25.7% higher than that of C3 crop. The optimal nitrogen utilization rates for wheat and corn were 253.20 kg·N·hm-2 and 239.84 kg·N·hm-2, respectively, and N fertilizer was more effective in reducing GHG of C3 crops. Among the 20 influencing factors, the relative impact of annual rainfall was the most significant, accounting for 69.3% of N2O and 40.39% of CO2 emissions, respectively. SCN had the most obvious impact on CH4、GWP and Greenhouse Gas Intensity (GHGI), reaching up to 51.45%、35.98% and 43.46%, This study quantitatively assessed the response of different types of crop yields and GHG emissions to cropland management practices and natural factors, and provided a basis for making management decisions to enhance global crop yields and reduce GHG.

Climate space, traits, and the spread of nonnative plants in North America

The future distribution of invading species depends on the climate space available and certain life history traits that facilitate invasion. Here, to predict the spread potential of plant species introduced in North America north of Mexico (NAM), we compiled distribution and life history data (i.e., seed size, life form, and photosynthetic pathways) for 3021 exotic plant species introduced to NAM. We comparatively examined the species’ range size and climate space in both native and exotic regions and the role of key life history traits. We found that large climate space for most exotic plants is still available in NAM. The range sizes in global exotic regions could better predict the current range sizes in NAM than those in global native regions or global native plus exotic regions. C3 species had larger ranges on average than C4 and CAM plants, and herbaceous species consistently showed stronger relationships in range size between native and exotic regions than woody species, as was the case within the C3 species group. Seed size was negatively related to range size both in native regions and in NAM. However, seed size surprisingly showed a positive correlation with global exotic range size and no correlation with the current actual global (native plus exotic) range size. Our findings underline the importance of species' native distribution and life history traits in predicting the spread of exotic species. Future studies should continue to identify potential climate space and use underappreciated species traits to better predict species invasions under changing climate.

Lithification of pelletal grains by microbially mediated organomineralization

Fecal pellets are key components of the biological carbon pump and a source of nutrients. When cohesively bound and cemented, they become the most abundant non-skeletal grains in shallow-water carbonates and an important nucleus for ooid formation. Herein, we describe the mineralization processes contributing to pellet cementation using scanning electron microscopy in conjunction with stable isotope and mineralogical analyses of the bulk sediments on Great Bahama Bank, known for its abundance of peloids and fecal pellets. Results show biogenic signatures consistent with the initial stages of organomineralization. These include, curved-tubular filaments and bacilli bacteria associated with extracellular polymeric substances (EPS); fibrils of EPS binding aragonite needles; and the coexistence of decayed EPS with amorphous calcium carbonate that once it develops, coalesces and crystalizes into aragonite. While δ13Cinorg do not show large variations, slightly higher values are observed in areas where pellets are indurated, likely attributed to photosynthetic activity on the pellets. The δ13Corg values tend to be more elevated in indurated pellets, suggesting that heterotrophs are preferentially using enriched carbon sources. In contrast, friable pellets from nearshore areas show more negative δ13Corg values, suggesting microbial exposure to depleted C3 and CAM plant sources. Fingerprints of nitrogen fixation and denitrification are also documented and supported by δ15Norg values. Altogether, these findings suggest that EPS and a microbial consortium, including gut-microbial flora and free-living surface colonizers, are responsible for inducing early cements, which are later complemented by secondary cements. Microorganisms involved in pellet lithification may subsequently also aid in ooid cortex development.

Xylem anatomical structure as a determinant of hydraulic trait variation in C3 plant Reaumuria soongorica and C4 plant Salsola passerina

Moisture variation significantly impacts hydraulic traits and xylem anatomical structure in woody plants, thereby influencing water transport and embolism resistance. However, the precise relationship between these factors within desert shrubs remains unclear, and it may be related to plant functional types. We conducted a water manipulation experiment involving seedlings of the C3 plant Reaumuria soongorica and the C4 plant Salsola passerina within a rain shelter. We applied three water treatments: control, chronic drought, and flash drought. After a period of drought treatment, seedlings were rewatered to control level for 15 days, after which hydraulic traits and anatomical structures were measured. We found that: (1) vessel density was positively correlated with sapwood specific conductivity for R. soongorica, while hydraulic weighted vessel diameter positively correlated with embolism resistance; both hydraulic weighted vessel diameter and vessel internal diameter span was positively correlated with sapwood specific conductivity for S. passerina; (2) R. soongorica had lower edge density yet higher modularity compared to S. passerina; (3) sapwood and leaf specific conductivity emerged as hub traits in R. soongorica, while vessel internal diameter span was identified as a hub trait in S. passerina, thus serving as important predictors of hydraulic function and related attributes. Our study demonstrates distinct hydraulic strategies in the two species. R. soongorica employs a highly modular trait combination to adapt to water fluctuations, maintaining both high hydraulic efficiency and embolism resistance under drought stress. Conversely, S. passerina integrates traits for efficient resource access, ensuring hydraulic efficiency but compromising embolism resistance under drought stress. Integrating hydraulic traits with anatomical structures significantly enhances predictions of desert shrub resilience to drought within the context of global climate change.

Forage ecology of Neotropical fish in Brazilian biomes using stable isotopes

Neotropical regions are responsible for harboring most of the global diversity of freshwater fish, providing essential ecosystem services for society. Human activities (e.g., land use changes) jeopardize aquatic ecosystems as well as species, communities, etc., impairing ecosystem services. We investigate the impact of human disturbance on the foraging ecology of Neotropical freshwater fishes across five Brazilian biomes by stable isotope analysis. We analyzed carbon (δ13C) and nitrogen (δ15N) isotopic compositions of Neotropical fishes, sourced from the SIA-BRA dataset. Fishes were categorized into herbivores, omnivores, and carnivores. We tested the correlation between human disturbances, indicated by the human disturbance index (hdi), and changes in fish diets. We expected that the assimilation of C4‑carbon from exotic forage would increase with higher disturbance levels, while δ15N levels would similarly rise due to nitrogen input from anthropogenic sources. We found increases in fish δ13C with human disturbance increases, suggesting greater assimilation of C4 carbon in places where native vegetation was replaced by C4 sources, confirmed by isotopic mixing models. In contrast, δ15N values did not show a significant relationship with human disturbance, probably due to the complex interactions and multiple sources of nitrogen in disturbed environments. Our finds suggest that stable isotope analysis provides a powerful tool for monitoring the effects of landscape changes on aquatic food webs. Particularly, the δ13C values of detritivorous fish that feed on C4 plant detritus could serve as bioindicators of environmental degradation. However, a specific isotopic characterization of each site would be valuable for more accurate niche information.

Carbon translocation within land snails affects the carbon isotopic fractionation

Stable carbon isotope composition (δ13C) of land snail materials is widely used as a proxy for reconstructing past vegetation and environmental changes. Interpretation δ13C data is challenging due to the complexities of snail physiology. This study cultured Lissachatina fulica (Bowdich, 1822) snails to investigate δ13C of their soft tissues and excrement under various plant types and dietary carbonate content. Our results show that snails primarily assimilate organic matter (OM), with limited use of dietary carbonates. δ13C of organic matter in excrement correlates positively with that in the diet, but exhibits deviations due to variable carbon isotopic fractionation during assimilation. Tissue δ13C (δ13Ctissue) is positively related to the δ13C of OM (δ13COM) in the diet, varying by turnover rates, with faster turnover rate, such as the digestive gland, exhibiting more negative δ13Ctissue values. Moreover, carbon isotopic fractionation between tissues and diet (Δ13Ctissue-OM) differs based on plant type. Snails fed with C3 plants show positive Δ13Ctissue-OM values, whereas those fed with C4 plants exhibit negative values. These Δ13Ctissue-OM values are far from equilibrium (Δ13Ctissue-OM = 0) with conditions of rapid snail growth. Our findings indicate that the snails fed with C3 and C4 plants result in distinct carbon isotopic fractionation, leading to the deviation in δ13C between plants and land snail materials (e.g., excrement, tissues, shells and shell-bound organic matter). A comprehensive model of carbon metabolism and isotopic fractionation in snails is proposed including the assimilation process from diet to soft tissues and excretion. This study highlights the importance of physiological factors such as growth rates and turnover rates when interpreting δ13C of land snail materials for paleoenvironmental reconstructions.

Exaptation of ancestral cell-identity networks enables C4 photosynthesis

C4 photosynthesis is used by the most productive plants on the planet, and compared with the ancestral C3 pathway, it confers a 50% increase in efficiency1. In more than 60 C4 lineages, CO2 fixation is compartmentalized between tissues, and bundle-sheath cells become photosynthetically activated2. How the bundle sheath acquires this alternate identity that allows efficient photosynthesis is unclear. Here we show that changes to bundle-sheath gene expression in C4 leaves are associated with the gain of a pre-existing cis-code found in the C3 leaf. From single-nucleus gene-expression and chromatin-accessibility atlases, we uncover DNA binding with one finger (DOF) motifs that define bundle-sheath identity in the major crops C3 rice and C4 sorghum. Photosynthesis genes that are rewired to be strongly expressed in the bundle-sheath cells of C4 sorghum acquire cis-elements that are recognized by DOFs. Our findings are consistent with a simple model in which C4 photosynthesis is based on the recruitment of an ancestral cis-code associated with bundle-sheath identity. Gain of such elements harnessed a stable patterning of transcription factors between cell types that are found in both C3 and C4 leaves to activate photosynthesis in the bundle sheath. Our findings provide molecular insights into the evolution of the complex C4 pathway, and might also guide the rational engineering of C4 photosynthesis in C3 crops to improve crop productivity and resilience3,4.

Hyphosphere core taxa link plant-arbuscular mycorrhizal fungi combinations to soil organic phosphorus mineralization

Arbuscular mycorrhizal (AM) fungi acquire photosynthetically fixed carbon (C) from host plants and transport some of it to hyphosphere bacteria via an extensive extraradical hyphal network. The hyphosphere microbiome, fostered by hyphal exudates, is crucial for AM fungi to access soil organic phosphorus (Po) and enhance plant growth, but the impact of plant-AM fungal combinations is still not well-elucidated. To answer this question, we selected two plant species with differing photosynthetic efficiency, medic (a C3 plant) and maize (a C4 plant), along with 4 AM fungal species, and successfully established various plant-AM fungal combinations. We examined the growth of plants and AM fungi, the mineralization process of soil Po, and the absolute quantity, community composition, and metabolic preferences of the hyphosphere microbiome.Maize-AM fungi combinations exhibited greater abilities to increase soil phosphatase activity and promote Po mineralization compared to medic-AM fungi combinations. This was related to substantial disparities in the hyphosphere core microbiome between maize and medic. Massilia, a pivotal member of the core microbiome and a keystone taxon within the hyphosphere network, showed a notably greater relative abundance in maize-AM fungal systems than in the medic treatment. Thirteen core bacterial strains isolated from the hyphosphere showed a universal ability to secrete phosphatase, with Massilia being the most proficient. Additionally, community level physiological profiles showed that the maize-associated hyphosphere microbiomes had a heightened capacity for metabolizing fructose and glucose, key components of hyphal exudates.Our study demonstrates that different combinations of plants and AM fungal species modulate the relative abundance of the core taxon through hyphal exudates, thus influencing the functionality of hyphosphere microbiomes for Po mineralization in the phytate-enriched soil. This provides novel insights into AM symbiosis for nutrient cycling and underscores the potential of tailored plant-fungal pairings in improving agricultural nutrient management and soil health.

Unlocking the adaptation mechanisms of the oleaginous microalga Scenedesmus sp. BHU1 under elevated salt stress: a physiochemical, lipidomics and transcriptomics approach.

Microalgae are vital for their photosynthetic abilities, contributing significantly to global oxygen production, serving as a key trophic level in aquatic ecosystems, aiding in biofuel production, assisting in wastewater treatment, and facilitating the synthesis of valuable biochemicals. Despite these advantages, photosynthetic microalgae are sensitive to salt stress, which alters their physiochemical and metabolic status, ultimately reducing microalgal growth. This sensitivity highlights the importance of understanding the impact of elevated salt content on the physiochemical, metabolic, and transcriptomic profiling of Scenedesmus sp., areas that are not yet fully understood. Our findings indicate that elevated salt stress decreases photosynthetic efficiency and increases non-regulated photochemical quenching of photosystem II (PSII). Moreover, PSII-driven linear electron flow (LEF) decreased, whereas photosystem I (PSI)-driven cyclic electron flow (CEF) increased in salt-stressed cells. To better understand the electron flow from PSII to PSI under elevated salt treatment, we analyzed the excitation energy flux per reaction center (RC), per cross-section (CS), energy flux ratios, and the potential index of PSII. Additionally, flow cytometry graphs depict the viability assay of Scenedesmus sp. BHU1. Our observations further revealed an increase in biochemical attributes, such as stress biomarkers, osmoprotectants, and enzymatic antioxidants, which help scavenge reactive oxygen species (ROS) under salt stress. Intracellular cations (Na + and Ca2+) were increased, while K+ levels decreased, indicating mechanisms of cellular homeostasis under salt stress. UHPLC-HRMS-based lipidome analysis confirmed that increasing salt stress induces the hyperaccumulation of several fatty acids involved in adaptation. Moreover, transcriptome analysis revealed the upregulation of genes associated with PSI, glycolysis, starch metabolism, sucrose metabolism, and lipid accumulation under salt stress. In contrast, genes related to PSII and C3 carbon fixation were downregulated to mitigate the adverse effects of salt stress.

Three-year elevated carbon dioxide concentration does not enhance soil organic carbon quantity due to simultaneously facilitated carbon input and decomposition in a single rice paddy soil evidenced by natural 13C tracing.

Soil organic carbon (SOC) markedly contributes to maintaining soil nutrient cycling and mitigating climate change. Elevated carbon dioxide concentration ([CO2]) is widely expected to improve crop yield and increase carbon (C) storage; however, its effects on rice growth and SOC dynamics remain greatly unclear. Therefore, a three-year (2007-2009) chamber experiment with two [CO2] treatments (380 vs. 680 ppm) was conducted during rice growing seasons. Ultisol soil, taken from a sugarcane (C4 plant) field on Ishigaki island, Okinawa, was used to grow rice (C3 plant). The natural 13C tracing method was utilized to measure the fraction of SOC derived from the rice plant, and δ13C values and concentrations of CO2 and CH4 dissolved in soil solutions were determined. Elevated [CO2] significantly increased rice aboveground biomass (AGB) by 11.8 %-28.8 % and assimilated C content by 12.2 %-28.3 %. However, no significant differences were observed in SOC, total nitrogen (N) content, and the C/N ratios between ambient and elevated [CO2]. Elevated [CO2] induced markedly lower δ13C values in both plant and soil samples relative to ambient [CO2]. The annual fractions of plant-derived C input ranged from 5.0 % to 21.2 % in ambient [CO2] and from 5.6 % to 21.9 % in elevated [CO2] without significant differences. Elevated [CO2] stimulated marked increases in dissolved CO2 and CH4 concentrations, and δ13C values of CH4, indicating a positive priming effect of elevated [CO2] on native SOC decomposition for methanogenesis. In conclusion, elevated [CO2] did not affect SOC accumulation by simultaneously increasing C input evidenced by increased AGB, and SOC decomposition as CO2 and CH4 emissions, hence resulting in a stable SOC quantity in rice paddy ecosystems. Our study delves in the nexus between C input and soil C decomposition under elevated CO2 condition, highlighting its significance in prediction of the responses of C storage in paddy ecosystems to future climate change.

Applied potassium negates osmotic stress impacts on plant physiological processes: a meta-analysis

Abstract Potassium (K) availability in plant cells is critical for maintaining plant productivity across many terrestrial ecosystems. Yet, there is no comprehensive assessment of the mechanisms by which plants respond to potassium application in such conditions, despite the global challenge of escalating osmotic stress. Herein, we conducted a meta-analysis using data from 2381 paired observations to investigate plant responses to potassium application across various morphological, physiological, and biochemical parameters under both osmotic and non-osmotic stress. Globally, our results showed the significant effectiveness of potassium application in promoting plant productivity (e.g., +12~30% in total dry weight), elevating photosynthesis (+12~30%), and alleviating osmotic damage (e.g., -19~26% in malonaldehyde), particularly under osmotic stress. Moreover, we found evidence of interactive effects between osmotic stress and potassium on plant traits, which were more pronounced under drought than salt stress, and more evident in C3 than C4 plants. Our synthesis verifies a global potassium control over osmotic stress, and further offers valuable insights into its management and utilization in agriculture and restoration efforts.

Evaluation of Foxtail Millet Varieties for Thermotolerance at Seedling Stage using Temperature Induction Response Technique (TIR)

In the present scenario of climate change, Foxtail millet is the best crop of choice and an indispensable component of dryland farming due to its C4 plant type and tolerance against the abiotic stresses. However, all the foxtail millet varieties may not sustain under severe temperature stress particularly at germination and seedling growth stages. Therefore, screening of varieties is required to identify the stress tolerant varieties in foxtail millet which can combat temperature stress at seed germination and early seedling growth stages which is the need of the hour under ever changing climatic conditions. Hence, A lab experiment was conducted to standardize the temperature induction response (TIR) protocol for foxtail millet seedlings using WGC-450 programmable plant growth chamber. Temperatures were standardized as sub lethal i.e. challenging temperatures as 38°C – 54°C for 5 hours and lethal temperatures as 56°C for 3 hours. Seven foxtail millet varieties (Suryanandi, SiA 3156, Srilakshmi, SiA 3085, Narasimharaya, Krishnadevaraya and Prasad) were screened for intrinsic tolerance using the standardized Thermo Induced Response (TIR) protocol. Out of the seven varieties evaluated, SiA 3085, Prasad, Suryanandi, Srilakshmi were identified to possess high level of thermo tolerance in terms of higher seedling survival with less reduction in root and shoot growth. The varieties with intrinsic heat tolerance can be explored for the development of heat stress tolerant varieties.

Photosynthetic efficiency of three C4 species is maintained under low light and high vapour pressure deficit

The photosynthetic efficiency of C4 plants could be impaired in environments with low light and high vapour pressure deficit (VPD). However, the interactive effect of low light and high VPD on C4 photosynthetic efficiency remains unexplored. We grew three C4 species, Setaria viridis L., Sorghum sudanense (Piper) Stapf., and Zea mays L., under controlled high and low irradiance and VPD conditions in growth chambers. Gas exchange and chlorophyll fluorescence parameters were measured to estimate apparent maximum quantum yield (QYmax), and 13C discrimination of leaf dry mass (ΔDM) was measured to estimate bundle-sheath leakiness (BS-leakiness). Averaged over VPD levels, net CO2 assimilation rate at saturating light (Asat) decreased in S. viridis and S. sudanense but not Z. mays under low irradiance. High VPD decreased Asat of S. viridis but increased Asat of Z. mays. QYmax was not significantly affected by low light, high VPD or their interaction, which was associated with the unchanged photochemical efficiency of photosystem II. Low light did not significantly influence BS-leakiness, while high VPD only increased BS-leakiness of Z. mays by 0.08 compared with low VPD at low irradiance. The insignificant interaction of low light and high VPD on QYmax and BS-leakiness indicates that these C4 species could maintain photosynthetic efficiency under these unfavourable conditions.

Complement activation by IgM autoantibodies linked to immune-mediated neuropathies depends on C2.

Complement factor C2 is a potential therapeutic target in immune-mediated neuropathies. However, literature suggests that classical complement pathway activation may proceed to C3 in the absence of C2, a so-called "C2 bypass." Here, we evaluated a C2 bypass mechanism during complement activation by pathogenic human IgM from patients with immune-mediated neuropathies. IgM autoantibodies from 51 patients with multifocal motor neuropathy (MMN) or anti-myelin-associated glycoprotein (MAG) neuropathy (AMN) were used to activate complement in exvivo disease models. C2 bypass was evaluated using C2-depleted (C2D) serum and a therapeutic anti-C2 antibody. In two different disease models of MMN, IgM anti-GM1 and IgM anti-GM2 autoantibodies from MMN patients were bound to induced pluripotent stem cell-derived motor neurons and Schwann cells, respectively, and fixed C3 upon incubation with fresh serum. C3 fixation was inhibited by anti-C2 and did not occur with C2D serum. Similarly, in an AMN model, IgM anti-MAG antibodies were incubated with fresh serum fixed C3, which in all cases was abrogated in the absence of C2 or in the presence of anti-C2. In exvivo disease models of MMN and AMN, complement activation by IgM autoantibodies from 51 patients was in all cases dependent on C2 and was inhibited by an antihuman C2 antibody. No evidence of a C2 bypass mechanism was found.

First report of Curvularia chiangmaiensis causing leaf spot in elephant grass in Brazil.

Elephant grass, Cenchrus purpureus, exhibits high efficiency in sequesting atmospheric CO2 during photosynthesis, leading to significant biomass production. As a C4 plant, it holds immense potential for alternative biodiesel production and serves as fresh feed for cattle (Negawo et al. 2018). Field observations in commercial pastures planted with elephant grass, located in the Brazilian cerrado, revealed necrotic leaf spots with a brownish center and a yellowish halo, reaching a severity of 30 to 50% between 2022 and 2023 in Palmas (10°24'08"S 48°21'45" W) and Gurupi (11°46'21"S 49°02'08" W), municipalities located in the state of Tocantins, Brazil. In both years, the field incidence of the disease on young and mature leaves approached 100% during the rainy season. Affected leaves were collected, packed in a thermal box, and taken to the phytopathology laboratory. The 198 leaves were sanitised in 1% hypochlorite for 30 seconds and washed thrice in sterile water. Upon sanitisation, leaf tissues were cut and cultured on potato dextrose agar (PDA) medium and incubated in a controlled chamber (BOD) at 28°C with a 12-hour photoperiod. Colonies exhibited a greyish colour with whitish edges, and the top plate was brownish, growing to a diameter of 5 cm over seven days. The colonies obtained from monosporic cultures formed curved conidia, predominantly with three septa, of a brownish colour, with lengths ranging from (7 µm to 14 µm and widths from 5 µm to 7 µm. (N=-50, Fig 1) (Yasanthika et al. 2023). The UFTCC01 isolate's DNA was extracted using the extraction kit (PROMEGA ®), amplified for genes (ITS, Gapdh and Tefα1), sequenced (OR345316.1, OR344427.1 and OR344428.1) and compared in BLASTn at Gen Bank deposited sequences. Phylogenetic analysis using the parsimony method in MEGA X identified the isolate as Curvularia chiangmaiensis, showing 99.5% identity with reference sequences (MN215651.1, MN264085.1, and MN263942.1). Concatenated region comparison revealed 94% similarity to sequences (OP564987.1 and MF490814.1) in the phylogenetic tree, confirming the species. The pathogenicity test used 60 seedlings of 50-day-old elephant grass, 30 of which were inoculated with a spore suspension (3.0 × 106 spores/mL) and 30 with sterile water. The solutions were sprayed twice. Only plants inoculated with the spore suspension exhibited symptoms akin to those observed in the field. Then, the fungus was reisolated from the lesions and Koch's postulates were confirmed twice.Previous studies have documented the C. chiangmaiensis pathogenicity in other grasses, such as maise in Thailand (Marin et al. 2017). Our studies constitute the first report of C. chiangmaiensis causing leaf spots on elephant grass in the Brazil.

Source apportionment of organic carbon and black carbon in the surface sediments of the Pearl River Estuary and its adjacent South China Sea: insight from stable carbon and nitrogen isotopes

Coastal estuaries and adjacent continental shelf seas constitute vital global carbon reservoirs, and the sources and transformations of organic carbon in these regions are crucial to global biogeochemical cycles and climate change. This study investigated the total organic carbon (TOC), total nitrogen (TN), black carbon (BC), and their stable carbon and nitrogen isotopes (δ15NTN, δ13CTOC, δ13CBC) in the surface sediments of the Pearl River Estuary (PRE) and its adjacent northern South China Sea (NSCS) aiming to assess the impact of human activities on organic carbon dynamics in these areas. Results showed that the highest TOC concentrations occurred in the inner PRE due to intense human activities, and decreased seaward. The west side of the PRE exhibited higher TOC levels than the east side, which was attributed to differences in hydrodynamic processes and human activities. The westward flow of the Pearl River diluted water, which carried terrestrial organic matter inputs due to the influence of the Coriolis effect and intense local human activities, was a primary contributor to higher TOC levels on the west side (terrestrial source). In contrast, increased productivity and intensive mariculture activities on the east side predominated as sources of organic matter (marine source). Similar to the TOC, BC and TN sources were mainly influenced by human activities. δ15NTN distribution shows that TN in the east side of PRE mainly originated from industrial wastewater input from the Pearl River, while in the east side TN was mainly from domestic sewage discharge. Additionally, BC sources have shifted from primarily biomass combustion in the 1990s to fossil fuel emissions presently. Isotopic analysis revealed that over 70% of BC originated from fossil fuel inputs and C3 plant combustion, highlighting the significant influence of human activities in the PRE and adjacent NSCS, and underscoring the need for effective management and protection of the eco-environment in these regions.

Isotopic analysis of modern sorghum and finger millet from different altitudes in Ethiopia: implications for ancient farming practices

C4 crops such as sorghum (Sorghum bicolor) and finger millet (Eleusine coracana) have played a significant role in the economic livelihood in arid and semi-arid zones of tropical and sub-tropical Africa since prehistoric times. However, to date, our knowledge of their past management practices is limited. Stable isotope analysis of archaeobotanical remains has been recognized as a valuable tool for reconstructing past agricultural practices, e.g. water management, and fertilization. Nonetheless, our limited understanding of the isotopic variability of C4 plants calls for further research on modern plant before application to archaeobotanical remains. In this paper, we aim to enhance our understanding of modern C4 botanical remains' isotopic variability by analyzing sorghum and finger millet plants. These crops were cultivated according to traditional local practices and collected from ten villages located in the Konso Zone (South Ethiopia) and Tigray Regional State (North Ethiopia), where they are among the daily ingredients for food, and traditional alcoholic and non-alcoholic drinks. We analyzed carbon and nitrogen stable isotopes of seeds and biosilica content in chaff, as it has been suggested that a relationship can exist between silicon and C:N. Carbon isotope values show significant variability, positively correlated with altitude. By demonstrating the sensitivity of C4 grain carbon stable isotope to altitude variations, which are likely connected to water availability, this study offers invaluable insights for the accurate assessment of isotopic values derived from ancient C4 crops. The absence of significant correlations with δ15N suggests that nitrogen isotope values may be less effective for understanding environmental variations in this kind of context. This highlights the limitations of nitrogen isotope data for interpreting ancient agricultural practices and underscores the importance of relying more on carbon isotopes for insights related to environmental conditions and altitude. Furthermore, we confirm that the amount of assimilated carbon may depend also on the biosilica content, which is in turn modulated by environmental parameters such as water availability or soil silicon levels.

Genome-wide comparative analysis of photosynthetic enzymatic genes provides novel insights into foxtail millet and other cereals.

C4 crops have more efficient photosynthetic pathways that enable their higher photosynthetic capacities as well as nitrogen and water use efficiencies than C3 crops. Previous research has demonstrated that the genomes of C3 species include and express every gene needed for the C4 photosynthesis pathway. However, very little is known about the dynamics and evolutionary history of such genetic evolution in C4 plants. In this study, the genes encoding five key photosynthetic pathway enzymes in the genomes of C3 (rice), C4 (maize, sorghum, and foxtail millet), and CAM (pineapple) crops were identified and compared systematically. The numbers of genes in these photosynthetic enzymes were highest in the C4 crops like sorghum and foxtail millet, while only eight genes were identified in the CAM plant. However, 16 genes were identified in the C3 crop rice. Furthermore, we performed physical, chemical, gene structure and, cis-element analyses to obtain complete insights into these key genes. Tissue-specific expressions showed that most of the photosynthetic genes are expressed in the leaf tissues. Comparisons of the expression characteristics confirmed that the expression patterns of non-photosynthetic gene copies were relatively conserved among the species, while the C4 gene copies in the C4 species acquired new tissue expression patterns during evolution. Additionally, multiple sequence features that could affect C4 gene expressions and subcellular localization were found in the coding and promoter regions. Our research also highlights the variations in how different genes have evolved within the C4 photosynthetic pathway, and we confirmed that specific high expressions in the leaves and right distribution within the cells were crucial for the development of the C4 photosynthetic abilities. The findings of this study are expected to aid in understanding the evolutionary process of the C4 photosynthetic pathway in grasses as well as offer insights for modifying the C4 photosynthetic pathways in wheat, rice, and other significant C3 cereal crops.

Engineered production of 5-aminolevulinic acid in recombinant Escherichia coli BL21.

5-aminolevulinic acid (ALA) is a non-protein amino acid that has been widely used in the fields of medicine and agriculture. This study aims to engineer the C5 pathway of the ALA biosynthesis in Escherichia coli BL21 to enhance ALA production. The ALA synthase genes gltX, hemA, and hemL were overexpressed in E. coli BL21 to lead to the increase in the production of ALA. The sRNA RyhB was also overexpressed to downregulate the expression of ALA dehydratase to reduce the downstream bioconversion of ALA to porphobilinogen. Next, the gene arcA was knocked out by CRISPR-Cas9 technology to open the TCA cycle to promote the respiratory metabolism of the strain to reduce the feedback inhibition of heme to ALA. The fermentation conditions of the engineered strain were optimized by response surface experiments. The time-course analysis of the ALA production was carried out in a 1 L shake flask. Through these efforts, the production of ALA in engineered strain reached 2953 mg/L in a 1 L shake flask. This study contributes to the industrial production of ALA by the engineered E. coli in the future.

Radiocarbon dating and isotopic paleoecology of Notiomastodon platensis (Mammalia: Proboscidea) from the late Pleistocene of Minas Gerais, Brazil

Proboscidea is a group of large mammals abundant in the fossil record and in Brazil it is represented by Notiomastodon platensis (Ameghino, 1888). To improve the understanding on its taxonomy, chronology, annual diet, and habitats paleoenvironmental aspects, we conducted a morphological description, absolute dating, and analysis of stable isotopes of carbon and oxygen (δ13C and δ18O) in Notiomastodon' remains from the northern (Norte de Minas) and western (Triângulo Mineiro) mesoregions of Minas Gerais State, Brazil. The material includes isolated teeth, mandibular portions, and postcranial bones at different levels of fragmentation, associated with at least eight adults and one juvenile. The only individual from Triângulo, found in Campina Verde municipality, was dated at 27,715–27,903 Cal yr BP. It presented a mixed diet based on C4 plants (piC4 = 90 %; δ13C = 0.5 ‰), which implies the occupation of an open environment, mostly pasture. The region was relatively humid (δ18O = 24.7 ‰), which is supported by the existence of humidity corridors in the Amazon region. A similar phytophysiognomy was inferred for the Norte de Minas region between at least 21,966–22,279 Cal yr BP and 18,944–19,157 Cal yr BP. However, one specimen showed a different δ13C value (piC3 = 0.87 %; δ13C = −10.2 ‰). This indicates it lived in a transitional environment between low-density forest and arboreal savannah. This likely occurred during a period that favored the expansion of trees and shrubs. The region underwent climate change, from relatively humid conditions (δ18O = 25.6 ± 0.2 ‰) to expressively dry (δ18O = 34.6 ‰) between the dated periods, a change corroborated by some palynological data. The multiannual paleoecological analysis, based on sequential sampling of three dentin layers of an incisor, indicated the relative stability of vegetation and climate despite fluctuations in hydrology. The perceived disassociation between vegetation dynamics and local hydrology corroborates the idea that factors other than precipitation may play a significant role in the environmental dynamics of the Cerrado biome.