Characterization of an extremophile bacterial acid phosphatase derived from metagenomics analysis.

Acid phosphatases are enzymes that play a crucial role in the hydrolysis of various organophosphorous molecules. A putative acid phosphatase called FS6 was identified using genetic profiles and sequences from different environments. FS6 showed high sequence similarity to type C acid phosphatases and retained more than 30% of consensus residues in its protein sequence. A histidine-tagged recombinant FS6 produced in Escherichia coli exhibited extremophile properties, functioning effectively in a broad pH range between 3.5 and 8.5. The enzyme demonstrated optimal activity at temperatures between 25 and 50°C, with a melting temperature of 51.6°C. Kinetic parameters were determined using various substrates, and the reaction catalysed by FS6 with physiological substrates was at least 100-fold more efficient than with p-nitrophenyl phosphate. Furthermore, FS6 was found to be a decamer in solution, unlike the dimeric forms of crystallized proteins in its family.

Functional expression, purification, biochemical and biophysical characterizations, and molecular dynamics simulation of a histidine acid phosphatase from Saccharomyces cerevisiae.

A histidine acid phosphatase (HAP) (PhySc) with 99.50% protein sequence similarity with PHO5 from Saccharomyces cerevisiae was expressed functionally with the molecular mass of ∼110 kDa through co-expression along with the set of molecular chaperones dnaK, dnaJ, GroESL. The purified HAP illustrated the optimum activity of 28.75 ± 0.39 U/mg at pH 5.5 and 40 ˚C. The Km and Kcat values towards calcium phytate were 0.608 ± 0.09 mM and 650.89 ± 3.6 s- 1. The half-lives (T1/2) at 55 and 60 ˚C were 2.75 min and 55 s, respectively. The circular dichroism (CD) demonstrated that PhySc includes 30.5, 28.1, 21.3, and 20.1% of random coils, α-Helix, ß-Turns, and ß-Sheet, respectively. The Tm recorded by CD for PhySc was 56.5 ± 0.34˚C. The molecular docking illustrated that His59 and Asp322 act as catalytic residues in the PhySc. MD simulation showed that PhySc at 40 ˚C has higher structural stability over those of the temperatures 60 and 80 ˚C that support the thermodynamic in vitro investigations. Secondary structure content results obtained from MD simulation indicated that PhySc consists of 34.03, 33.09, 17.5, 12.31, and 3.05% of coil, helix, turn, sheet, and helix310, respectively, which is almost consistent with the experimental results.

Short-term responses of soil enzyme activities and stoichiometry to litter input in Castanopsis carlesii and Cunninghamia lanceolata plantations.

Litter input triggers the secretion of soil extracellular enzymes and facilitates the release of carbon (C), nitrogen (N), and phosphorus (P) from decomposing litter. However, how soil extracellular enzyme activities were controlled by litter input with various substrates is not fully understood. We examined the activities and stoichiometry of five enzymes including ß-1,4-glucosidase, ß-D-cellobiosidase, ß-1,4-N-acetyl-glucosaminidase, leucine aminopeptidase and acidic phosphatase (AP) with and without litter input in 10-year-old Castanopsis carlesii and Cunninghamia lanceolata plantations monthly during April to August, in October, and in December 2021 by using an in situ microcosm experiment. The results showed that: 1) There was no significant effect of short-term litter input on soil enzyme activity, stoichiometry, and vector properties in C. carlesii plantation. In contrast, short-term litter input significantly increased the AP activity by 1.7% in May and decreased the enzymatic C/N ratio by 3.8% in August, and decreased enzymatic C/P and N/P ratios by 11.7% and 10.3%, respectively, in October in C. lanceolata plantation. Meanwhile, litter input increased the soil enzymatic vector angle to 53.8° in October in C. lanceolata plantations, suggesting a significant P limitation for soil microorganisms. 2) Results from partial least squares regression analyses showed that soil dissolved organic matter and microbial biomass C and N were the primary factors in explaining the responses of soil enzymatic activity to short-term litter input in both plantations. Overall, input of low-quality (high C/N) litter stimulates the secretion of soil extracellular enzymes and accelerates litter decomposition. There is a P limitation for soil microorganisms in the study area.

Trade-offs between root-secreted acid phosphatase and root morphology traits, and their contribution to phosphorus acquisition in Brassica napus.

Oilseed rape (Brassica napus) is one of the most important oil crops in the world and shows sensitivity to low phosphorus (P) availability. In many soils, organic P (Po) is the main component of the soil P pool. Po must be mineralised to Pi through phosphatases, and then taken up by plants. However, the relationship between root-secreted acid phosphatases (APase) and root morphology traits, two important P-acquisition strategies in response to P deficiency, is unclear among B. napus genotypes. This study aimed to understand their relationship and how they affect P acquisition, which is crucial for the sustainable utilisation of agricultural P resources. This study showed significant genotypic variations in root-secreted APase activity per unit root fresh weight (SAP) and total root-secreted APase activity per plant (total SAP) among 350 B. napus genotypes. Seed yield was positively correlated with total SAP but not significantly correlated with SAP. Six root traits of 18 B. napus genotypes with contrasting root biomass were compared under normal Pi, low Pi and Po. Genotypes with longer total root length (TRL) reduced SAP, but those with shorter TRL increased SAP under P deficiency. Additionally, TRL was important in P-acquisition under three P treatments, and total SAP was also important in P-acquisition under Po treatment. In conclusion, trade-offs existed between the two P-acquisition strategies among B. napus genotypes under P-deficient conditions. Total SAP was an important root trait under Po conditions. These results might help to breed B. napus with greater P-acquisition ability under low P availability conditions.

Dredging wastewater discharge from shrimp ponds affects mangrove soil physical-chemical properties and enzyme activities.

Dredging wastewater discharge is a significant environmental concern for mariculture near mangrove ecosystems. However, little attention has been paid to its effects on the soil physical-chemical properties and enzyme activities in mangrove habitats. This study compared the soil physical-chemical properties and enzyme activities in the polluted area that received dredging wastewater from a shrimp pond with those in the control area without wastewater to explore the effects of wastewater discharge on the soil physical-chemical properties and enzyme activities. Variations in soil physical-chemical properties and enzyme activities across different tidal flat areas and depths were also examined. The polluted area exhibited lower soil salinity (10.47 ± 0.58 vs. 15.64 ± 0.54) and moisture content (41.85 ± 1.03 % vs. 45.81 ± 1.06 %) than the control area. Wastewater discharge increased soil enzyme activities, (acid phosphatase, protease, and catalase), resulting in higher inorganic nitrogen (13.20 ± 0.00 µg g-1 vs. 11.60 ± 0.03 µg g-1) but lower total nitrogen (0.93 ± 0.01 mg g-1 vs. 1.62 ± 0.11 mg g-1) in the contaminated zone. From the control to polluted area, there was an approximate increase of 0.43 and 0.83 mg g-1 in soil total phosphorus and soluble phosphate, driven by increased acid phosphatase. However, soil humus and organic matter decreased by 0.04 and 1.22 %, respectively, because of wastewater discharge. The impact of wastewater discharge on the soil physical-chemical properties and enzyme activities was most pronounced in the landward and surface soil layers (0-5 cm). The results showed that wastewater discharge altered soil physical-chemical properties and enzyme activities, accumulating soil bioavailable nutrients (inorganic nitrogen and soluble phosphate), but at the cost of reduced soil quality, especially organic matter, further adversely affecting the overall health of mangrove ecosystems. Prioritizing the management of wastewater discharged from mariculture adjacent to mangrove forests is crucial for mangrove conservation.

Lysosomal enzymes and the oxygen burst capability of monocyte-derived macrophages in active drug-resistant tuberculosis patients in relation to cell attachment.

Drug resistance to tuberculosis (TB) has become an obstacle in eliminating tuberculosis. The transmission of drug-resistant TB from patients increases the incidence of primary drug-resistant (DR) TB in individuals who are in close contact. Therefore, it is necessary to incorporate an immunological approach into preventive therapy. This study focuses on the activity of lysosomal enzymes, oxygen bursts, and the attachment ability of macrophages among individuals diagnosed with active drug-resistant TB compared with close contacts with latent TB or healthy cases. We measured macrophage oxygen burst ability (Water-soluble tetrazolium salt (WST) test, Nitric Oxide production, and myeloperoxidase activity) and the degradative ability of lysosomes (activity of the ß-glucuronidase and acid phosphatase enzymes). Six active DR-TB patients and 18 close-contact cases (8 Latent Tuberculosis Infection (LTBI); 10 healthy) were recruited at Universitas Indonesia Hospital. The macrophage attachment of the LTBI group was higher than in the other groups. NO production, myeloperoxidase activity, ß-glucuronidase, and acid phosphatase were higher in the active DR-TB group. A negative correlation was uncovered between phagocytosis and NO production, myeloperoxidase activity, and lysosomal enzymes. The difference in macrophage function is expected to be a further reference in active DR-TB treatment or preventive therapy.

Mn-modified porphyrin metal-organic framework mediated colorimetric and photothermal dual-channel probe for sensitive detection of organophosphorus pesticides.

Herein, a novel dual-mode probe for organophosphorus pesticides (OPs) colorimetric and photothermal detection was developed based on manganese modified porphyrin metal-organic framework (PCN-224-Mn). PCN-224-Mn had excellent oxidase-like activity and oxidized colorless 3,3,5,5-tetramethylbenzidine (TMB) to blue-green oxidation state TMB (oxTMB), which exhibited high temperature under near-infrared irradiation. l-ascorbate-2-phosphate was hydrolyzed by acid phosphatase to produce ascorbic acid, which weakened colorimetric and photothermal signals by impacting oxTMB generation. The presence of OPs blocked the production of ascorbic acid by irreversibly inhibiting the activity of acid phosphatase, causing the restoration of chromogenic reaction and the increase of temperature. Under the optimal conditions, the probe showed a good linear response to OPs in the concentration range of 5 âˆ¼ 10000 ng/mL, using glyphosate as the analog. The detection limits of glyphosate in colorimetric mode and photothermal mode were 1.47 ng/mL and 2.00 ng/mL, respectively. The probe was successfully used for sensitive identification of OPs residues in tea, brown rice, and wheat flour. This work proposes a simple and reliable colorimetric/photothermal platform for OPs identification, which overcomes the problem that single-mode detection probes are susceptible to external factors, and has broad application potential in the field of food safety.

Acid phosphatase involved in phosphate homeostasis in Brassica napus and the functional analysis of BnaPAP10s.

Purple acid phosphatases (PAPs) are involved in activating the rhizosphere's organic phosphorus (P) and promoting P recycling during plant development, especially under the long-term P deficiency conditions in acid soil. However, the function of BnaPAPs in response to P deficiency stress in Brassica napus has rarely been explored. In this study, we found that the acid phosphatase activities (APA) of rapeseed shoot and root increased under P deficienct conditions. Genome-wide identification found that 82 PAP genes were unevenly distributed on 19 chromosomes in B. napus, which could be divided into eight subfamilies. The segmental duplication events were the main driving force for expansion during evolution, and the gene structures and conserved motifs of most members within the same subfamily were highly conservative. Moreover, the expression levels of 37 and 23 different expressed genes were induced by low P in leaf and root, respectively. BnaA09.PAP10a and BnaC09.PAP10a were identified as candidate genes via interaction networks. Significantly, both BnaPAP10a overexpression lines significantly increased root-related APA and total phosphate concentration under P deficiency and ATP supply conditions, thereby improving plant growth and root length. In summary, our results provided a valuable foundation for further study of BnaPAP functions.

SlPHL1 positively modulates acid phosphatase in response to phosphate starvation by directly activating the genes SlPAP10b and SlPAP15 in tomato.

Increased acid phosphatase (APase) activity is a prominent feature of tomato (Solanum lycopersicum) responses to inorganic phosphate (Pi) restriction. SlPHL1, a phosphate starvation response (PHR) transcription factor, has been identified as a positive regulator of low Pi (LP)-induced APase activity in tomato. However, the molecular mechanism underlying this regulation remains to be elucidated. Here, SlPHL1 was found to positively regulate the LP-induced expression of five potential purple acid phosphatase (PAP) genes, namely SlPAP7, SlPAP10b, SlPAP12, SlPAP15, and SlPAP17b. Furthermore, we provide evidence that SlPHL1 can stimulate transcription of these five genes by binding directly to the PHR1 binding sequence (P1BS) located on their promoters. The P1BS mutation notably weakened SlPHL1 binding to the promoters of SlPAP7, SlPAP12, and SlPAP17b but almost completely abolished SlPHL1 binding to the promoters of SlPAP10b and SlPAP15. As a result, the transcriptional activation of SlPHL1 on SlPAP10b and SlPAP15 was substantially diminished. In addition, not only did transient overexpression of either SlPAP10b or SlPAP15 in tobacco leaves increase APase activity, but overexpression of SlPAP15 in Arabidopsis and tomato also increased APase activity and promoted plant growth. Subsequently, two SPX proteins, SlSPX1 and SlSPX4, were shown to physically interact with SlPHL1. Moreover, SlSPX1 inhibited the transcriptional activation of SlPHL1 on SlPAP10b and SlPAP15 and negatively regulated the activity of APase. Taken together, these results demonstrate that SlPHL1-mediated LP signaling promotes APase activity by activating the transcription of SlPAP10b and SlPAP15, which may provide valuable insights into the mechanisms of tomato response to Pi-limited stress.

Purification, identification and Cryo-EM structure of prostatic acid phosphatase in human semen.

Prostatic acid phosphatase (PAP) is a glycoprotein that plays a crucial role in the hydrolysis of phosphate ester present in prostatic exudates. It is a well-established indicator for prostate cancer due to its elevated serum levels in disease progression. Despite its abundance in semen, PAP's influence on male fertility has not been extensively studied. In our study, we report a significantly optimized method for purifying human endogenous PAP, achieving remarkably high efficiency and active protein recovery rate. This achievement allowed us to better analyze and understand the PAP protein. We determined the cryo-electron microscopic (Cryo-EM) structure of prostatic acid phosphatase in its physiological state for the first time. Our structural and gel filtration analysis confirmed the formation of a tight homodimer structure of human PAP. This functional homodimer displayed an elongated conformation in the cryo-EM structure compared to the previously reported crystal structure. Additionally, there was a notable 5-degree rotation in the angle between the α domain and α/ß domain of each monomer. Through structural analysis, we revealed three potential glycosylation sites: Asn94, Asn220, and Asn333. These sites contained varying numbers and forms of glycosyl units, suggesting sugar moieties influence PAP function. Furthermore, we found that the active sites of PAP, His44 and Asp290, are located between the two protein domains. Overall, our study not only provide an optimized approach for PAP purification, but also offer crucial insights into its structural characteristics. These findings lay the groundwork for further investigations into the physiological function and potential therapeutic applications of this important protein.

Empirical evidence challenges the effectiveness of the enzymatic stoichiometry of glucosidase and phosphatase as an indicator of microbial C vs P limitation.

The ratio of ß-1,4-glucosidase (BG) to acid/alkaline phosphomonoesterase (AP) (BG:AP) is commonly employed as an indicator to assess the relative microbial limitations of carbon (C) and phosphorus (P), whereby a higher BG:AP ratio suggests stronger C limitations. This approach is based on the assumption that BG and AP can represent enzymes targeting C and P, respectively. Nevertheless, it is crucial to recognize that microbial C and P acquisition involves the participation of other enzymes alongside BG and AP, and thus, the capacity of BG and AP to accurately and comprehensively represent the entire spectrum of C and P acquisition is questionable. Here, analyzing previously published data, I present a piece of empirical evidence that challenges the suitability of the BG:AP ratio as an accurate indicator of microbial limitations concerning C vs P. P fertilization decreased BG:AP in up to 27 % out of the total 109 observations, which represents a clear contradiction, as this outcome is interpreted by the enzymatic stoichiometry approach as indicating an intensified P limitation arising from P fertilization. Furthermore, the effect of P fertilization on the BG:AP ratio did not show significant differences between experimental sites characterized by higher BG:AP ratios (indicative of lesser P limitation) and those with lower BG:AP ratios (indicative of greater P limitation). Consequently, I conclude that the BG:AP ratio inadequately reflects microbial C vs P limitations.

Inhibition effect of epicatechin gallate on acid phosphatases from rainbow trout (Oncorhynchus mykiss) liver by multispectral and molecular docking.

Inhibition of acid phosphatase, which significantly contributes to inosine 5'-monophosphate (IMP) degradation, is crucial for preventing flavor deterioration of aquatic products during storage. In this study, the inhibitory effect of epicatechin gallate (ECG) on the activity of acid phosphatase isozymes (ACPI and ACPII) was analyzed using inhibition kinetics, fluorescence spectroscopy, isothermal titration calorimetry, and molecular simulation. ACPI and ACPII with molecular weights of 59.5 and 37.3 kDa, respectively, were purified from rainbow trout liver. ECG reversibly inhibited ACPI and ACPII activities via mixed-type inhibition, with half maximal inhibitory concentration (IC50) of 0.24 ± 0.01 mmol/L and 0.27 ± 0.03 mmol/L, respectively. Fluorescence spectra indicated that ECG statically quenched the intrinsic fluorescence of ACPI and ACPII. ECG could spontaneously bind to ACPI and ACPII through hydrogen bonding and van der Waals forces and exhibited a higher affinity for ACPI than for ACPII. In addition, molecular dynamic simulation revealed that ECG-ACPI and ECG-ACPII complexes were relatively stable during the entire simulation process. Our findings provide a theoretical basis for the use of ECG as an inhibitor of ACP to improve the flavor of aquatic products.

Effects of Setaria viridis on heavy metal enrichment tolerance and bacterial community establishment in high-sulfur coal gangue.

Plant enrichment and tolerance to heavy metals are crucial for the phytoremediation of coal gangue mountain. However, understanding of how plants mobilize and tolerate heavy metals in coal gangue is limited. This study conducted potted experiments using Setaria viridis as a pioneer remediation plant to evaluate its tolerance to coal gangue, its mobilization and enrichment of metals, and its impact on the soil environment. Results showed that the addition of 40% gangue enhanced plant metal and oxidative stress resistance, thereby promoting plant growth. However, over 80% of the gangue inhibited the chlorophyll content, photoelectron conduction rate, and biomass of S. viridis, leading to cellular peroxidative stress. An analysis of metal resistance showed that endogenous S in coal gangue promoted the accumulation of glutathione, plant metal chelators, and non-protein thiols, thereby enhancing its resistance to metal stress. Setaria viridis cultivation affected soil properties by decreasing nitrogen, phosphorus, conductivity, and urease and increasing sucrase and acid phosphatase in the rhizosphere soil. In addition, S. viridis planting increased V, Cr, Ni, As, and Zn in the exchangeable and carbonate-bound states within the gangue, effectively enriching Cd, Cr, Fe, S, U, Cu, and V. The increased mobility of Cd and Pb was correlated with a higher abundance of Proteobacteria and Acidobacteria. Heavy metals, such as As, Fe, V, Mn, Ni, and Cu, along with environmental factors, including total nitrogen, total phosphorus, urease, and acid phosphatase, were the primary regulatory factors for Sphingomonas, Gemmatimonas, and Bryobacter. In summary, S. viridis adapted to gangue stress by modulating antioxidant and elemental enrichment systems and regulating the release and uptake of heavy metals through enhanced bacterial abundance and the recruitment of gangue-tolerant bacteria. These findings highlight the potential of S. viridis for plant enrichment in coal gangue areas and will aid the restoration and remediation of these environments.

Characterization of haloacid dehalogenase superfamily acid phosphatase from Staphylococcus lugdunensis.

The haloacid dehalogenase superfamily implicated in bacterial pathogenesis comprises different enzymes having roles in many metabolic pathways. Staphylococcus lugdunensis, a Gram-positive bacterium, is an opportunistic human pathogen causing infections in the central nervous system, urinary tract, bones, peritoneum, systemic conditions and cutaneous infection. The haloacid dehalogenase superfamily proteins play a significant role in the pathogenicity of certain bacteria, facilitating invasion, survival, and proliferation within host cells. The genome of S. lugdunensis encodes more than ten proteins belonging to this superfamily. However, none of them have been characterized. The present work reports the characterization of one of the haloacid dehalogenase superfamily proteins (SLHAD1) from Staphylococcus lugdunensis. The functional analysis revealed that SLHAD1 is a metal-dependent acid phosphatase, which catalyzes the dephosphorylation of phosphorylated metabolites of cellular pathways, including glycolysis, gluconeogenesis, nucleotides, and thiamine metabolism. Based on the substrate specificity and genomic analysis, the physiological function of SLHAD1 in thiamine metabolism has been tentatively assigned. The crystal structure of SLHAD1, lacking 49 residues at the C-terminal, was determined at 1.7 Å resolution with a homodimer in the asymmetric unit. It was observed that SLHAD1 exhibited time-dependent cleavage at a specific point, occurring through a self-initiated process. A combination of bioinformatics, biochemical, biophysical, and structural studies explored unique features of SLHAD1. Overall, the study revealed a detailed characterization of a critical enzyme of the human pathogen Staphylococcus lugdunensis, associated with several life-threatening infections.

Mycorrhizal fungus Serendipita indica-associated acid phosphatase rescues the phosphate nutrition with reduced arsenic uptake in the host plant under arsenic stress.

Symbiotic interactions play a vital role in maintaining the phosphate (Pi) nutrient status of host plants and providing resilience during biotic and abiotic stresses. Serendipita indica, a mycorrhiza-like fungus, supports plant growth by transporting Pi to the plant. Despite the competitive behaviour of arsenate (AsV) with Pi, the association with S. indica promotes plant growth under arsenic (As) stress by reducing As bioavailability through adsorption, accumulation, and precipitation within the fungus. However, the capacity of S. indica to enhance Pi accumulation and utilization under As stress remains unexplored. Axenic studies revealed that As supply significantly reduces intracellular ACPase activity in S. indica, while extracellular ACPase remains unaffected. Further investigations using Native PAGE and gene expression studies confirmed that intracellular ACPase (isoform2) is sensitive to As, whereas extracellular ACPase (isoform1) is As-insensitive. Biochemical analysis showed that ACPase (isoform1) has a Km of 0.5977 µM and Vmax of 0.1945 Unit/min. In hydroponically cultured tomato seedlings, simultaneous inoculation of S. indica with As on the 14thday after seed germination led to hyper-colonization, increased root/shoot length, biomass, and induction of ACPase expression and secretion under As stress. Arsenic-treated S. indica colonized groups (13.33 µM As+Si and 26.67 µM As+Si) exhibited 8.28-19.14 and 1.71-3.45-fold activation of ACPase in both rhizospheric media and root samples, respectively, thereby enhancing Pi availability in the surrounding medium under As stress. Moreover, S. indica (13.33 µM As+Si and 26.67 µM As+Si) significantly improved Pi accumulation in roots by 7.26 and 9.46 times and in shoots by 4.36 and 8.85 times compared to the control. Additionally, S. indica induced the expression of SiPT under As stress, further improving Pi mobilization. Notably, fungal colonization also restricted As mobilization from the hydroponic medium to the shoot, with a higher amount of As (191.01 ppm As in the 26.67 µM As+Si group) accumulating in the plant's roots. The study demonstrates the performance of S. indica under As stress in enhancing Pi mobilization while limiting As uptake in the host plant. These findings provide the first evidence of the As-Pi interaction in the AM-like fungus S. indica, indicating reduced As uptake and regulation of PHO genes (ACPase and SiPT genes) to increase Pi acquisition. These data also lay the foundation for the rational use of S. indica in agricultural practices.

Multi-omics analysis reveals the roles of purple acid phosphatases in organic phosphorus utilization by the tropical legume Stylosanthes guianensis.

Stylo (Stylosanthes guianensis) is a tropical legume known for its exceptional tolerance to low phosphate (Pi), a trait believed to be linked to its high acid phosphatase (APase) activity. Previous studies have observed genotypic variations in APase activity in stylo; however, the gene encoding the crucial APase responsible for this variation remains unidentified. In this study, transcriptomic and proteomic analyses were employed to identify eight Pi starvation-inducible (PSI) APases belonging to the purple APase (PAP) family in the roots of stylo and seven in the leaves. Among these PSI-PAPs, SgPAP7 exhibited a significantly positive correlation in its expression levels with the activities of both internal APase and root-associated APase across 20 stylo genotypes under low-Pi conditions. Furthermore, the recombinant SgPAP7 displayed high catalytic activity toward adenosine 5'-diphosphate (ADP) and phosphoenolpyruvate (PEP) in vitro. Overexpression (OE) of SgPAP7 in Arabidopsis facilitated exogenous organic phosphorus utilization. Moreover, SgPAP7 OE lines showed lower shoot ADP and PEP levels than the wild type, implying that SgPAP7 is involved in the catabolism and recycling of endogenous ADP and PEP, which could be beneficial for plant growth in low-Pi soils. In conclusion, SgPAP7 is a key gene with a major role in stylo adaptation to low-Pi conditions by facilitating the utilization of both exogenous and endogenous organic phosphorus sources. It may also function as a PEP phosphatase involved in a glycolytic bypass pathway that minimizes the need for adenylates and Pi. Thus, SgPAP7 could be a promising target for improving tolerance of crops to low-Pi availability.

Assessment of degradation mechanism of imidacloprid residues in grape rhizosphere soil by UHPLC-Orbitrap™-MS and its residual impact on soil enzyme activity.

Imidacloprid (IM) is a systemic insecticide persistent in the environment and possesses a negative impact on the non-targeted ecosystem. The objective of the present study was to evaluate the dissipation and degradation mechanism of IM residues in grape rhizosphere soil and to investigate its residual effect on soil enzyme activity at different IM spiking levels. The half-life of IM residue in soil was 27, 36, and 43.5 days at a spiking level of 1, 10, and 50 mg kg-1, respectively following a bi-phasic first + first-order dissipation kinetics. UHPLC-Orbitrap™-MS analysis by targeted metabolomics approach revealed that IM metabolites such as IM-amine analogue, guanidine (reduction), 5-hydroxy IM (hydroxylation), IM-Urea (oxidation), reduced NO analogue of IM (oxidation), and olefin of guanidine IM (dehydrogenation) were identified and proposed the degradation mechanism in grape rhizosphere soil. Toxicity of IM residues on five extracellular enzymes, viz., dehydrogenase, acid phosphatase, alkaline phosphatase, ß-glucosidase, and urease revealed that activity of dehydrogenase, acid phosphatase, and alkaline phosphatase remained unaffected at 60th day of sampling. The ß-glucosidase and urease were negatively affected throughout the incubation period indicating the influence of IM residues on carbon and nitrogen mineralization in soil. Thus, long-term exposure of IM to grape rhizosphere through soil drenching could affect soil enzyme activity which has a negative effect on the soil nutrient cycle and soil microbiome.

Multi-imaging platform for rhizosphere studies: Phosphorus and oxygen fluxes.

Rhizosphere is a soil volume of high spatio-temporal heterogeneity and intensive plant-soil-microbial interactions, for which visualization and process quantification is of highest scientific and applied relevance, but still very challenging. A novel methodology for quick assessment of two-dimensional distribution of available phosphorus (P) in rhizosphere was suggested, tested, and development up to the application platform. Available P was firstly trapped by an in-situ diffusive gradients in thin-films (DGT) sampler with precipitated zirconia as the binding gel, and subsequently, the loaded gel was analyzed with an optimized colorimetric imaging densitometry (CID). The imaging platform was established linking: i) DGT, ii) planar optode, and iii) soil zymography techniques to simultaneously determine available P, oxygen, and acid phosphatase in rhizosphere at sub-millimeter spatial scales. The DGT identified available P level in rice rhizosphere were spatially overlapping to the localized redox hotspots and phosphatase activity. The spatial relationship between available P and acid phosphatase activity was dependent on root development. The root radial oxygen loss (ROL) remained active during the experimental observations (2-3 days), while a flux of available P of 10 pg cm-2 s-1 was visualized within 2-3 mm of roots, confirming the correlative response of rice roots to oxygen secretion and P uptake. Summarizing, the established imaging platform is suitable to capture spatial heterogeneity and temporal dynamics of root activities, nutrient bioavailability, ROL and enzyme activities in rhizosphere.

High-resolution chemical imaging to understand Cd activation in rice rhizosphere of karstic soils.

Cadmium (Cd) activation, especially at a high spatial resolution, in paddy soils with a high geogenic Cd background is yet to be understood. To investigate the temporal and spatial patterns of Cd activation in rice rhizosphere, pot and rhizotron experiments were conducted using four paddy soils with high geogenic Cd (0.11-3.70 mg kg-1) from Guangxi, southwestern China. The pot experiment results showed that porewater Cd concentrations initially decreased and then increased over the complete rice growth period, reaching its lowest value during the late-tillering and early-filling stages. Besides, correlation analysis identified organic matter and root manganese (Mn) content as the main factors affecting rice Cd uptake, with Mn having a negative effect and organic matter having a positive effect. Sub-millimeter two-dimensional chemical imaging revealed that the distribution of labile Cd in the rhizosphere (by diffusive gradients in thin-films, or DGT) was influenced by the root system and soil properties, such as pH (by planar optode) and acid phosphatase activity (by soil zymography). Soil acid phosphatase activity increased under Cd stress. The overall pH at rice rhizosphere decreased. Moreover, a close relationship was found between the spatial distributions of soil labile Mn and Cd at the rhizosphere, with higher Mn being associated with lower Cd lability. This study highlights Mn as a key element in regulating rice Cd uptake and enlightens future Mn-based strategies for addressing Cd pollution in rice paddy soils, especially in karst areas with high geochemical background.