Rice straw returning enhances cadmium activation by accelerating iron cycling thus hydroxyl radical production in paddy soils during drainage.

Straw returning is widely found elevating the bioavailability of cadmium (Cd) in paddy soils with unclear biogeochemical mechanisms. Here, a series of microcosm incubation experiments were conducted and spectroscopic and microscopic analyses were employed. The results showed that returning rice straw (RS) efficiently increased amorphous Fe and low crystalline Fe (II) to promote the production of hydroxyl radicals (OH) thus Cd availability in paddy soils during drainage. On the whole, RS increased OH and extractable Cd by 0.2-1.4 and 0.1-3.3 times, respectively. While the addition of RS effectively improved the oxidation rate of structural Fe (II) mineral (i.e., FeS) to enhance soil Cd activation (up to 38.5 %) induced by the increased OH (up to 69.2 %). Additionally, the existence of CO32- significantly increased the efficiency level on OH production and Cd activation, which was attributed to the improved reactivity of Fe (II) by CO32- in paddy soils. Conclusively, this study emphasizes risks of activating soil Cd induced by RS returning-derived OH, providing a new insight into evaluating the safety of straw recycling.

Progress of Polymer Electrolytes Worked in Solid-State Lithium Batteries for Wide-Temperature Application.

Solid-state Li-ion batteries have emerged as the most promising next-generation energy storage systems, offering theoretical advantages such as superior safety and higher energy density. However, polymer-based solid-state Li-ion batteries face challenges across wide temperature ranges. The primary issue lies in the fact that most polymer electrolytes exhibit relatively low ionic conductivity at or below room temperature. This sensitivity to temperature variations poses challenges in operating solid-state lithium batteries at sub-zero temperatures. Moreover, elevated working temperatures lead to polymer shrinkage and deformation, ultimately resulting in battery failure. To address this challenge of polymer-based solid-state batteries, this review presents an overview of various promising polymer electrolyte systems. The review provides insights into the temperature-dependent physical and electrochemical properties of polymers, aiming to expand the temperature range of operation. The review also further summarizes modification strategies for polymer electrolytes suited to diverse temperatures. The final section summarizes the performance of various polymer-based solid-state batteries at different temperatures. Valuable insights and potential future research directions for designing wide-temperature polymer electrolytes are presented based on the differences in battery performance. This information is intended to inspire practical applications of wide-temperature polymer-based solid-state batteries.

Rice straw biochar and lime regulate the availability of heavy metals by managing colloid-associated- but dissolved-heavy metals.

Heavy metal (HM) pollution has extensively spread in agricultural soils, posing potential threats to food safety and human health. Biochar and lime are two amendments used to remediate the soils contaminated with HMs. However, colloids have been shown to increase the mobility of HMs in paddy soils. Nevertheless, limited investigations have been made into the impact of biochar and lime on the formation of colloid-associated (colloidal) HMs in paddy soils. In this study, column and microcosm incubation experiments were conducted to examine how biochar and lime affected the availability of HMs (arsenic, cadmium, copper, iron, manganese, lead, and zinc) in different layers of paddy soils. The results revealed that biochar significantly inhibited the formation of colloidal HMs in the soil flooding phase, whereas the lime increased the colloidal HMs. These colloids containing HMs were identified as poorly dissolved metal sulfides. When the soil was drained, colloidal HMs transformed into dissolved forms, thereby improving the availability of HMs. Biochar decreased HM availability by reducing colloidal- but dissolved- HMs, whereas lime had the opposite effect. Hence, biochar demonstrated a stable and reliable remediation ability to decrease HM availability in paddy soil during flooding and drainage processes. In conclusion, this study highlighted that biochar efficiently reduced HM availability by mitigating the formation of colloidal HMs during flooding and their transformation into dissolved HMs during drainage in paddy soils.

Influence of sulfate reducing bacteria cultured from the paddy soil on the solubility and redox behavior of Cd in a polymetallic system.

As a toxic heavy metal, cadmium (Cd) easily enters into rice while rice grains greatly contribute to the dietary Cd intake in the populations consuming rice as a staple food. The availability of Cd in paddy soil determines the accumulation of grain Cd. Soil drainage leads to the remobilization of Cd, increasing bioavailability of Cd. In contrast, soil flooding results in little contribution of soil Cd to grain Cd, which is generally attributed to sulfate reduction induced by sulfate-reducing bacteria (SRB) in paddy soils. However, effects of SRB cultured from the paddy soil on the solubility and redox behavior of Cd have been seldom investigated before. Here, we used SRB enrichment cultures to investigate the temporal dynamics of Cd2+. The results showed that SRB enrichment cultures efficiently reduced solution redox potential (Eh) to less than -100 mV and gradually increased pH to neutral, demonstrating their ability to create a good anaerobic environment. The solubility of Cd obviously decreased in the anaerobic phase and Cd2+ was transformed into poorly dissolved CdS near the SRB cell wall edge. The addition of Zn2+ and/or Fe2+ further improved the decrease in Cd solubility and facilitated the formation of polymetallic sulfides as a consequence of promoting the production of S0 and dissolved sulfides (S2-/HS-) and the transformation of S0 into S2-/HS-. Little of Cd was detected in the media upon reoxidation, which was probably due to the high pH and the interaction between CdS and ZnS/FeS. Conclusively, these results demonstrate the detailed dynamic processes that explain the essential role of SRB in regulating the redox dynamics of chalcophile heavy metals and their bioavailability in paddy soils.

The role of the ABF1 gene in regulation of Cd-induced hormesis in Arabidopsis thaliana.

Hormesis is important in plant performance in contaminated environments, but the underlying genetic mechanisms are poorly understood. This study aimed at mining key genes in regulating Cd-induced hormesis in Arabidopsis thaliana and verifying their biological function. Hormesis of fresh weight, dry weight, and root length occurred at concentrations of 0.003-2.4, 0.03-0.6, and 0.03-0.6 µM Cd, respectively. Superoxide dismutase and catalase activities, and chlorophyll content displayed inverted U-shaped curves, indicating that the antioxidant defense system and photosynthesis system played roles in hormesis. Based on KEGG pathway analysis with the trend chart of differentially expressed genes and weighted correlation network analysis, the key gene ABF1 in the metabolic pathway of abscisic acid was identified. Subsequently, genetic experiments with wild, overexpressing, and knockdown lines of A. thaliana were conducted to further verify the biological function of ABF1 involving Cd-induced hormesis in A. thaliana. The results revealed that the resistance capability of the overexpressing type to Cd stress was significantly enhanced and implicated that the ABF1 gene is essential for Cd-induced hormesis in A. thaliana. Mining key genes that regulate Cd-induced hormesis in plants and stimulate them could have a transformative impact on the phytoremediation of metal-contaminated environments.

New insights into the role of soil properties in driving cadmium-induced hormesis in soil alkaline phosphatase under vegetation cover change.

This study investigated the hormetic responses of soil alkaline phosphatase (ALP) to exogenous Cd under five different vegetation cover types in a typical coastal wetland, including mudflat (Mud), Phragmites australis (PA), Spartina alterniflora (SA), Metasequoia glyptostroboides (MG), and Cinnamomum camphora (CC). The results showed that the activity of soil ALP was significantly enhanced by exogenous 0.3-1.0, 0.2-0.8, 0.05-0.3, 0.05-0.6, and 0.05-0.60 mg Cd /kg in Mud, PA, SA, MG, and CC, respectively. Moreover, the Horzone (an integrated indicator of the stimulation phase) of Mud and PA was significantly higher than that of SA, MG, and CC. Multiple factor analysis revealed that soil chemical properties and soil bacteria community play an important role in the hormetic effect of soil ALP to Cd stress. Soil electric conductivity (EC) and the relative abundance of Gammaproteobacteria were also identified as key drivers of the hormetic effects of Cd on soil ALP under five vegetation cover types. These findings suggest that the soil ecosystem had better resistance to exogenous Cd stress under mudflat and native species (PA) than invasive species (SA), and artificial forests (MG and CC) when soil ALP activity was the test endpoint. Consequently, this study is beneficial for future ecological risk assessment of soil Cd contamination under divergent vegetation covers.

Pig farm biogas slurry can effectively reduce the pH of saline-alkali soils.

Pig farm biogas slurry is being increasingly used as a potent organic fertilizer for sustainable agriculture under circular economy. However, the effect of biogas slurry on soil pH is currently controversial, and the underlying mechanisms especially in saline-alkali soils are not well understood. A saline-alkali soil (pH = 9.2, EC = 2.0 ms/cm) was selected for soil column (0-50 cm) experiments with (BS) and without (CK) addition of pig farm biogas slurry to investigate the soil pH change and its driving factors. Our results show that the soil pH under CK ranged between 9.1 and 9.5 across different soil depths. Compared to CK, the BS-treated soil had lower pH at 0-20 cm depth and higher pH at 20-30 cm depth (P < 0.01). The soil NH4+-N concentrations were negatively correlated with pH values under BS (P < 0.01), indicating that the oxidation of ammonium mainly contributed to the decrease of soil pH. Interestingly, the anions, such as Cl-, SO42- and NO3-, were accumulated in the topsoil (0-20 cm) under BS, resulting in the changed correlations of these anions with Na+ when compared to the control. FT-IR and 13C-NMR spectra uncovered that carboxyl, amide C, and total alkyl C groups may be responsible for reducing pH of the saline-alkali soil tested. The soil surface morphology confirmed a much tighter granular aggregate microstructure when mixing the biogas slurry with the soil. Overall, we concluded that from the perspective of soil pH, the utilization of biogas slurry for improving saline-alkali soil is feasible and sustainable.

How Does Adjacent Land Use Influence Sediment Metals Content and Potential Ecological Risk in the Hongze Lake Wetland?

Metal pollution in lake wetlands has become increasingly serious in China and worldwide due to the rapid growth of urbanization and agricultural activities. However, comprehensive assessments of metal pollution in lake wetland sediments that are associated with land use change have been limited from an international perspective. Metal concentrations (As, Cd, Cr, Cu, Hg, Mn, Pb, and Zn) were measured in the surface soils and surrounding sediments of five land use types in the eastern Hongze Lake wetlands, including Farmland (FL), Culture Ponds (CP), Reed Land (RL), Poplar Forests (PF), and Willow Forests (WF). The metal pollution status was assessed using the geo-accumulation index and the potential ecological risk index; The results showed that the average concentrations of As, Cd, Mn, and Zn in the surface soils and As, Cd, Cu, and Zn in the sediments, exceeded the background values of Jiangsu Province, China. The FL soils and surrounding sediments were moderately contaminated with As, whereas the sediments surrounding the CP were uncontaminated to moderately contaminated with Cd. Metal pollution in both soils and sediments was greater on farmland than on other types of land use. Furthermore, there were significant positive correlations between the values of the soil risk index and the values of the surrounding sediment risk index. Correlation analysis (CA) and principal component analysis (PCA) found that metals may be derived from agricultural activities such as the application of chemical and organic fertilizers, as well as domestic sewage, industrial wastewater, and geological anomalies. These findings shed new light on the quantitative impacts of adjacent land use practices on sediment metal pollution and provide a scientific foundation for wetland management decision-making.

Waste-to-Resource Strategy to Fabricate Functionalized MOFs Composite Material Based on Durian Shell Biomass Carbon Fiber and Fe3O4 for Highly Efficient and Recyclable Dye Adsorption.

Recently, metal-organic frameworks (MOFs), which are porous inorganic-organic hybrid materials consisting of metal ions (clusters or secondary building units) and organic ligands through coordination bonds, have attracted wide attention because of their high surface area, huge ordered porosity, uniform structural cavities, and excellent thermal/chemical stability. In this work, durian shell biomass carbon fiber and Fe3O4 functionalized metal-organic framework composite material (durian shell fiber-Fe3O4-MOF, DFM) was synthesized and employed for the adsorption removal of methylene blue (MB) from wastewater. The morphology, structure, and chemical elements of the DFM material were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), transmission electron microscope (TEM), and X-ray photoelectron spectroscope (XPS) techniques. Adsorption conditions such as pH, adsorption time, and temperature were optimized. The adsorption isotherm and kinetics results show that the adsorption process of DFM material to MB is more in line with the Freundlich model and pseudo-second-order kinetic model. Using these models, the maximum adsorption capacity of 53.31 mg/g was obtained by calculation. In addition, DFM material could be easily reused through an external magnet and the removal rate of MB was still 80% after five adsorption cycles. The obtained results show that DFM composite material, as an economical, environmentally friendly, recyclable new adsorbent, can simply and effectively remove MB from wastewater.

Preparation of monoclonal antibody and development of an enzyme-linked immunosorbent assay for the detection of ceftiofur in animal-derived foods.

Ceftiofur (CEF) residues in animal-derived foods are of great concern to farmers, regulatory agencies and consumers. In this study, an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) method was established to quickly monitor CEF residues in edible animal tissues using an easy sample preparation procedure. A monoclonal antibody, 4D5, against CEF has been produced at first, which had IC50 values for CEF, ceftriaxone, cefquinome, cefotaxime and desfuroylceftiofur of 0.78 µg/L, 0.73 µg/L, 13.6 µg/L, 8.99 µg/L and 8.89 µg/L, respectively. The limit of detection (LOD) and limit of quantitation (LOQ) in artificially contaminated animal-derived foods were 0.12-0.19 µg/L and 0.20-0.30 µg/L. The recovery rates were in the range of 89.7-109.0%. The CVs were less than 6.7%. A good correlation (R= 0.9994) between the ic-ELISA and UPLC-MS/MS showed the reliability of the developed ic-ELISA. The ic-ELISA produces a sensitive, accurate and low-cost tool for the screening of residues of CEF in animal-derived foods.

Measurement and modeling of hormesis in soil bacteria and fungi under single and combined treatments of Cd and Pb.

Heavy metals are considered major environmental pollutants. Soil microorganisms represent a predominant component of soils ecosystems, yet there is little information regarding hormetic responses of soil microorganisms to single and combined exposures to heavy metals. In the present study, to explore and predict the hormetic response of soil microorganisms, dose-response relationships of bacterial and fungal populations to single and combined treatments of cadmium (Cd) and lead (Pb) were evaluated. The results revealed hormetic responses of bacterial and fungal populations to both single and combined Cd and Pb treatments. The maximum stimulation (Mmax; relative to control treatment with no metals) of bacterial and fungal populations was 40% at 2 mg Cd/kg and 60% at 160 mg Pb/kg. An enhanced Mmax occurred in bacterial (50%) and fungal (75%) populations in the presence of the binary mixtures of 0.6 mg Cd/kg + 160 mg Pb/kg and 4.0 mg Cd/kg + 200 mg Pb/kg, suggesting positive additivity. This study showed that the hormetic effects of the mixtures were related to the independent effect of Cd and Pb, but they could not be predicted by the single effect of Cd or Pb. These new findings of the hormetic response of soil microorganisms to single treatments of Cd and Pb and their binary mixtures can facilitate the determination and minimization of ecological risks in heavy metal-polluted soils.

Hormetic responses of soil microbiota to exogenous Cd: A step toward linking community-level hormesis to ecological risk assessment.

We investigated hormetic responses of soil microbial communities to exogenous Cd by assessing microbial count, bacterial and fungal abundance, and microbial community diversity. We found that the bacterial count (BC) decreased (3-40%) by 0.2-40 mg Cdkg-1. Addition of 0.6-2.0 mgkg-1 significantly increased fungal count (FC) by 7-42%, while addition of 4.0-40 mgkg-1 Cd decreased FC by 29-51%, indicating a hormetic dose response. We also found that the FC/BC ratio increased by 0.6-2.0 mg Cdkg-1, with a maximum stimulation of 51%, and decreased (18-27%) by 4.0-40 mg Cdkg-1. Cd had no adverse effect on the α-diversity of bacterial or fungal communities. For relative abundances (RAs) of bacteria and fungi at phylum level, Bacteroidetes RA exhibited a biphasic dose-response curve, with an 18-24% increase at 0.6-4.0 mgkg-1 and a 10% decrease at 40 mgkg-1 compared with control. The results of FC, FC/BC, and Bacteroidetes RAs suggest that hormesis occurred at microbial community level, with positive effects occurring at 0.6-2.0 mgkg-1. This study can contribute to incorporating microbial community hormesis into the ecological risk assessments in the future.

The role of bacterial communities in shaping Cd-induced hormesis in 'living' soil as a function of land-use change.

Bacterial communities and soil physicochemical properties shape soil enzymes activities. However, how environmental factors and bacterial communities affect the relationship between increasing doses of soil pollutants and soil alkaline phosphatase (ALP), an index of soil microbiota activity, remains poorly understood. In this study, we investigated the response of soil ALP to 13 doses of Cd (0 and 0.01-100 mg/kg) under four land uses, viz. grassland (GL), natural forest (NF), plantation forest (PF), and wheat field (WF). We found that Cd commonly induced hormetic-like responses of soil ALP, with a maximum stimulation of 10.7%, 10.1%, 11.6%, and 14.5% in GL, NF, PF, and WF, respectively. The size of the hormetic zone (Horzone), an integrated indicator of the stimulation phase and biological plasticity, was in the order GL > WF > PF > NF, and the hormetic zone occurred in the dose range of 5-10, 0.3-10, 0.8-3, and 3-5 mg/kg, respectively. These results indicate highly pleiotropic responses of 'living' soil system to promote resilience to Cd contamination, with soil microbiota potentially contributing to soil ALP's hormetic-like response under different land uses. The hormetic-like response of 'living' soil ALP in different land uses offers a new insight into the identification and minimization of the ecological risks of land-use change in Cd-contaminated lands.

Chromophorylation of a Novel Cyanobacteriochrome GAF Domain from Spirulina and Its Response to Copper Ions.

Cyanobacteriochromes (CBCRs) are phytochrome-related photoreceptor proteins in cyanobacteria and cover a wide spectral range from ultraviolet to far-red. A single GAF domain that they contain can bind bilin(s) autocatalytically via heterologous recombination and then fluoresce, with potential applications as biomarkers and biosensors. Here, we report that a novel red/green CBCR GAF domain, SPI1085g2 from Spirulina subsalsa, covalently binds both phycocyanobilin (PCB) and phycoerythrobilin (PEB). The PCB-binding GAF domain exhibited canonical red/green photoconversion with weak fluorescence emission. However, the PEB-binding GAF domain, SPI1085g2-PEB, exhibited an intense orange fluorescence (λabs.max = 520 nm, λfluor.max = 555 nm), with a fluorescence quantum yield close to 1.0. The fluorescence of SPI1085g2-PEB was selectively and instantaneously quenched by copper ions in a concentration-dependent manner and exhibited reversibility upon treatment with the metal chelator EDTA. This study identified a novel PEB-binding cyanobacteriochrome-based fluorescent protein with the highest quantum yield reported to date and suggests its potential as a biosensor for the rapid detection of copper ions.

Cd induced biphasic response in soil alkaline phosphatase and changed soil bacterial community composition: The role of background Cd contamination and time as additional factors.

Hormesis is an intriguing phenomenon characterized by low-dose stimulation and high-dose inhibition. The hormetic phenomena have been frequently reported in the past decades, but the researches on the biphasic responses of soil enzymes are still limited. The main objective of this study is to explore dose response of alkaline phosphatase (ALP) to Cd (0, 0.003, 0.03, 0.3, 3.0 and 30 mg/kg) in the presence of different levels of background Cd contamination (bulk soil with no added Cd, BS; low background Cd, LB; medium background Cd, MB; and high background Cd, HB). ALP activity at 0.003-0.3 mg Cd/kg was 13-39% higher than that of the control (0 mg Cd/kg) for HB after 7 d. Similarly, the enzyme activities at 0.003-0.03 mg Cd/kg were 2-25% and 14-17% higher than those of the controls for MB and HB after 60 d. After 90 d, ALP activities at 0.3-3.0 mg Cd/kg increased by 11-17% for LB. The dose-response curves had the shape of an inverted U, showing biphasic responses at days 7 (HB), 60 (MB and HB) and 90 (LB). After 60 days of exposure, total operational taxonomic units (OTU) numbers and unique species exposed to Cd stress displayed hormetic-response curve for MB. The relative abundances of Agrobacterium, Salinimicrobiums, Bacilllus, and Oceanobacillus displayed significantly positive correlations with ALP activity. This suggested that bacterial communities potentially contribute to ALP's hormesis. This study further provides new insights into the ecological mechanisms of pollutant-induced hormesis, and substantially contributes to the ecological risk assessment of Cd pollution.

The PPR-SMR Protein ATP4 Is Required for Editing the Chloroplast rps8 mRNA in Rice and Maize.

Chloroplast gene expression involves the participation of hundreds of pentatricopeptide repeat (PPR) RNA binding proteins, and proteins in the PLS subfamily typically specify sites of RNA editing, whereas those in the P-subfamily typically stabilize RNA, activate translation, or promote intron splicing. Several P-type PPR proteins include a small MutS-related (SMR) domain, but the biochemical contribution of the SMR domain remains enigmatic. Here, we describe a rice (Oryza sativa) mutant, osatp4, lacking the ortholog of ATP4, a PPR-SMR protein in maize (Zea mays). osatp4 mutants were chlorotic and had a plastid-ribosome deficiency when grown in the cold. Like maize ATP4, OsATP4 was required for the accumulation of dicistronic rpl16-rpl14 transcripts. Surprisingly, OsATP4 was also required for the editing of a specific nucleotide in the ribosomal protein S8 transcripts, rps8, and this function was conserved in maize. By contrast, rps8 RNA was edited normally in the maize PROTON gradient regulation3 mutant, pgr3, which also lacks rpl16-rpl14 transcripts, indicating that the editing defect in atp4 mutants is not a secondary effect of altered rpl16-rpl14 RNA metabolism. Expression of the edited rps8 isoform in transgenic osatp4 mutants complemented the cold-sensitive phenotype, indicating that a rps8 expression defect accounts for the cold-sensitivity. We suggest that ATP4 stimulates rps8 editing by facilitating access of a previously characterized PLS-type RNA editing factor to its cognate cis-element upstream of the edited nucleotide.

Toluene induces hormetic response of soil alkaline phosphatase and the potential enzyme kinetic mechanism.

Hormesis of soil enzyme that involved in heavy metal has been attracting much more attention for risk assessment of heavy metal toxicity, but insufficient studies were conducted to define the hormetic responses induced by toluene or other organic pollutions. The objectives of this study were to investigate the hormetic responses of soil enzyme induced by toluene and explore the potential enzyme kinetic mechanism. Soil alkaline phosphatase (ALP) activity was regarded as the endpoint to explore the hormetic responses under different doses of toluene (0.0, 0.1, 0.5, 1.0, 2.0, 3.0, 5.0, 10.0, 50.0 and 100.0 µL g-1). Subsequently, we conducted the experiments of enzymatic reaction kinetics and pure enzyme to further verify the potential mechanisms of soil ALP's hormesis. Results showed that ALP activities at 0.1-1.0 µL g-1 toluene were significantly increased in contrast to the control (0 µL g-1 toluene) (P < 0.05) at the exposure time of 30, 36, 48 and 54 h, with the maximum stimulation magnitudes of 24-43%. ALP activities were almost not affected by toluene (2-100 µL L-1) in the whole experimental period (6-54 h). Meanwhile, the values of catalytic efficiency (the radio Vmax/Km, Vmax: maximum reaction velocity and Km: Michaelis constant) and Vmax significantly increased compared with the control, but the value of Km decreased from 2.5 to 1.6. Overall, low dose toluene can induce hormesis of soil ALP. The potential reason is that low-dose toluene could enhance the combination of soil ALP and substrates. We believe that this study will provide a new viewpoint for ecological risk assessment of toluene contaminated soils.

Novel compact high-speed passive gamma-ray assay equipment for uranium enrichment measurement of fuel rods.

Uranium enrichment measurement is an essential quality inspection for fuel rods before delivery to users. Generally, compared with active neutron assay (ANA) equipment, passive gamma-ray assay (PGA) equipment is more economical and safer. However, the current PGA equipment based on photomultipliers is too slow (1 m/min) to meet the growing needs in China. Recently, we have developed a set of compact high-speed PGA equipment including four detection modules (128 units in total), a 128-channel data acquisition system (DAS), a power supply, special software, and an automatic loading and unloading mechanism. The detection unit is based on silicon photomultipliers in virtue of its compact size and good performance. The DAS processes signals of all units in parallel into a sequence of data packets carrying the energy information and the corresponding unit ID. The software integrates the data packets into a fluctuating count curve in a time-delay superposition method and identifies possible abnormal pellets. After calibrations, our equipment can locate abnormal pellets accurately at a speed of 6 m/min. In addition, it can directly measure the enrichment of fresh pellets not in secular equilibrium without waiting for two months. So far, the equipment has been successfully run for one year on the assembly line of China North Nuclear Fuel Co. and shows good potential to replace the traditional ANA equipment.

Accumulation of the RNA polymerase subunit RpoB depends on RNA editing by OsPPR16 and affects chloroplast development during early leaf development in rice.

Plastid-encoded genes are coordinately transcribed by the nucleus-encoded RNA polymerase (NEP) and the plastid-encoded RNA polymerase (PEP). Resulting primary transcripts are frequently subject to RNA editing by cytidine-to-uridine conversions at specific sites. The physiological role of many editing events is largely unknown. Here, we have used the CRISPR/Cas9 technique in rice to knock out a member of the PLS-DYW subfamily of pentatricopeptide repeat (PPR) proteins. We found that OsPPR16 is responsible for a single editing event at position 545 in the chloroplast rpoB messenger RNA (mRNA), resulting in an amino acid change from serine to leucine in the ß-subunit of the PEP. In striking contrast to loss-of-function mutations of the putative orthologue in Arabidopsis, which were reported to have no visible phenotype, knockout of OsPPR16 leads to impaired accumulation of RpoB, reduced expression of PEP-dependent genes, and a pale phenotype during early plant development. Thus, by editing the rpoB mRNA, OsPPR16 is required for faithful plastid transcription, which in turn is required for Chl synthesis and efficient chloroplast development. Our results provide new insights into the interconnection of the finely tuned regulatory mechanisms that operate at the transcriptional and post-transcriptional levels of plastid gene expression.

Lysobacter may drive the hormetic effects of Pb on soil alkaline phosphatase.

It has become increasingly recognized that hormesis phenomena exist in soil ecosystem, but the research on the hormetic responses of soil enzymes are still limited. This study was conducted to investigate the hormetic effects of lead (Pb) on the activity of soil alkaline phosphatase (ALP) and the associated microbial groups. Soils were treated by adding Pb (NO3)2 solution with 0, 10, 100, 500, 1000, 2000, 4000, and 5000 mg/kg of Pb, respectively. A moist heat sterilization method (121 °C × 30 min) was used to discriminate the microbial effect on soil ALP hormesis from other factors. The bacterial community composition and abundance in the control (CK) and Pb-treated soils were detected by the high-throughput sequencing technique. The ALP activity at doses of 500-1000 mg/kg of Pb was significantly higher than that of CK (0 mg/kg of Pb), showing a typical inverted U-shaped dose response with the stimulation magnitude of 9.8-10.3% within 48 h of incubation. In addition, ALP activity decreased by 80% on average after soil sterilization. Analysis of bacterial community composition indicated that the relative abundance of Lysobacter at 1000 mg Pb/kg was higher than that of CK at genus level, with the increase of 69.82%. The highly significant correlation between soil ALP activities and relative abundance of Lysobacter indicated that this bacterial genus could possibly contribute to the hormetic responses of soil ALP to added doses of Pb in soils.