An optimal combined slow-release nitrogen fertilizer and urea can enhance the decomposition rate of straw and the yield of maize by improving soil bacterial community and structure under full straw returning system.

Under a full straw returning system, the relationship between soil bacterial community diversity and straw decomposition, yield, and the combined application of slow-release nitrogen and urea remains unclear. To evaluate these effects and provide an effective strategy for sustainable agricultural production, a 2-year field positioning trial was conducted using maize as the research object. Six experimental treatments were set up: straw returning + no nitrogen fertilizer (S1N0), straw returning + slow-release nitrogen fertilizer:urea = 0:100% (S1N1), straw returning + slow-release nitrogen fertilizer:urea = 30%:70% (S1N2), straw returning + slow-release nitrogen fertilizer:urea = 60%:40% (S1N3), straw returning + slow-release nitrogen fertilizer:urea = 90%:10% (S1N4), and straw removal + slow-release nitrogen fertilizer:urea = 30%:70% (S0N2). Significant differences (p < 0.05) were observed between treatments for Proteobacteria, Acidobacteriota, Myxococcota, and Actinobacteriota at the jointing stage; Proteobacteria, Acidobacteriota, Myxococcota, Bacteroidota, and Gemmatimonadota at the tasseling stage; and Bacteroidota, Firmicutes, Myxococcota, Methylomirabilota, and Proteobacteria at the maturity stage. The alpha diversity analysis of the soil bacterial community showed that the number of operational taxonomic units (OTUs) and the Chao1 index were higher in S1N2, S1N3, and S1N4 compared with S0N2 at each growth stage. Additionally, the alpha diversity measures were higher in S1N3 and S1N4 compared with S1N2. The beta diversity analysis of the soil bacterial community showed that the bacterial communities in S1N3 and S1N4 were more similar or closely clustered together, while S0N2 was further from all treatments across the three growth stages. The cumulative straw decomposition rate was tested for each treatment, and data showed that S1N3 (90.58%) had the highest decomposition rate. At the phylum level, straw decomposition was positively correlated with Proteobacteria, Actinobacteriota, Myxococcota, and Bacteroidota but significantly negatively correlated with Acidobacteriota. PICRUSt2 function prediction results show that the relative abundance of bacteria in soil samples from each treatment differed significantly. The maize yield of S1N3 was 15597.85 ± 1477.17 kg/hm2, which was 12.80 and 4.18% higher than that of S1N1 and S0N2, respectively. In conclusion, a combination of slow-release nitrogen fertilizer and urea can enhance the straw decomposition rate and maize yield by improving the soil bacterial community and structure within a full straw returning system.

CO2 Photoreduction over Semiconducting 2D Materials with Supported Single Atoms: Recent Progress and Challenges.

In the face of the growing energy crisis and environmental challenges, substantial efforts are now directed toward sustainable clean energy as a replacement for traditional fossil fuels. CO2 photoreduction into value-added chemicals and fuels is widely recognized as a promising approach to mitigate current energy and environmental concerns. Photocatalysts comprising single atoms (SAs) supported on two-dimensional (2D) semiconducting materials (SAs-2DSemi) have emerged as a novel frontier due to the combined merits of SA catalysts and 2D materials. In this study, we review advancements in metal SAs confined on 2DSemi substrates, categorized into four groups: (1) metal oxide-based, (2) g-C3N4-based, (3) emerging, and (4) hybridized 2DSemi, for photocatalytic CO2 conversion over the past few years. With a particular focus on highlighting the distinct advantages of SAs-2DSemi, we delve into the synthesis of state-of-the-art catalysts, their catalytic performances, and mechanistic elucidation facilitated by experimental characterizations and theoretical calculations. Following this, we outline the challenges in this field and offer perspectives on harnessing the potential of SAs-2DSemi as promising photocatalysts. This comprehensive review aims to provide valuable insights for the future development of 2D photocatalytic materials involving SAs for CO2 reduction.

Effects of slow-release nitrogen and urea combined application on soil physicochemical properties and fungal community under total straw returning condition.

Under the system of full straw returning, the relationship between soil fungal community diversity and soil physiochemical properties, and the combined application of slow-release nitrogen and urea is unclear. To evaluate its effect and provide an effective strategy for sustainable agricultural production, a 2-year field positioning trial was conducted using maize as the research object. The experiment was designed with two factors: straw treatment(S) and nitrogen fertilizer treatment(N),Six experimental treatments were set up,S1N0,S1N1,S1N2,S1N3,S1N4,S0N2,respectively.Analysis of 54 soil samples revealed 15 fungal phyla and 49 fungal classes. The composition of fungal communities in each treatment was basically the same, but there were significant differences in species abundance. Under total straw returning conditions, the combined application of slow-release nitrogen fertilizer and normal nitrogen fertilizer significantly increased the relative abundance of Ascomycota. During the jointing stage, tasseling stage and maturity stage, S1N4, S1N3 and S1N2 increased by 25.76%, 22.97%, 20.74%; 25.11%, 30.02%, 23.64% and 22.47%, 28.14%, 22.71% respectively compared with S0N2.The relative abundance of Basidiomycota was significantly reduced. Alpha diversity analysis showed that the straw returning mode significantly increased the Shannon index and decreased the Simpson index, which was obvious in the jointing stage and tasseling stage. The principal coordinate analysis analysis results showed that the fungal communities formed different clusters in the horizontal and vertical directions at the three growth stages of corn jointing, tasseling and maturity. At the jointing stage and tasseling stage, the communities of the straw return treatment and the straw removal treatment were separated, and the community distribution of each treatment was not significantly different in the mature stage. Total straw returning combined with slow-release fertilizer significantly (P＜0.05) increased the soil organic carbon, nitrate nitrogen and ammonia nitrogen content in each growth period, and increased the soil total nitrogen and hydrolyzable nitrogen content (P＞0.05).After the straw was returned to the field, the combined application of slow-release nitrogen fertilizer and common urea had a significant impact on soil urease, catalase, and sucrase activities. Among them, the three enzyme activities were the highest in the S1N3 treatment at the jointing stage and maturity stage, and the S1N4 treatment at the tasseling stage had the highest enzyme activity. Fungal community composition is closely related to environmental factors. Soil organic carbon, urease and catalase are positively correlated with Ascomycota and negatively correlated with Basidiomycota.

Biochar's role in improving pakchoi quality and microbial community structure in rhizosphere soil.

Background: Biochar amendments enhance crop productivity and improve agricultural quality. To date, studies on the correlation between different amounts of biochar in pakchoi (Brassica campestris L.) quality and rhizosphere soil microorganisms are limited, especially in weakly alkaline soils. The experiment was set up to explore the effect of different concentrations of biochar on vegetable quality and the correlation between the index of quality and soil bacterial community structure changes. Methods: The soil was treated in the following ways via pot culture: the blank control (CK) without biochar added and with biochar at different concentrations of 1% (T1), 3% (T2), 5% (T3), and 7% (T4). Here, we investigatedthe synergistic effect of biochar on the growth and quality of pakchoi, soil enzymatic activities, and soil nutrients. Microbial communities from pakchoi rhizosphere soil were analyzed by Illumina MiSeq. Results: The results revealed that adding 3% biochar significantly increased plant height, root length, and dry weight of pakchoi and increased the contents of soluble sugars, soluble proteins, Vitamin C (VC), cellulose, and reduced nitrate content in pakchoi leaves. Meanwhile, soil enzyme activities and available nutrient content in rhizosphere soil increased. This study demonstrated that the the microbial community structure of bacteria in pakchoi rhizosphere soil was changed by applying more than 3% biochar. Among the relatively abundant dominant phyla, Gemmatimonadetes, Anaerolineae, Deltaproteobacteria and Verrucomicrobiae were reduced, and Alphaproteobacteria, Gammaproteobacteria, Bacteroidia, and Acidimicrobiia relative abundance increased. Furthermore, adding 3% biochar reduced the relative abundance of Gemmatimonas and increased the relative abundances of Ilumatobacter, Luteolibacter, Lysobacter, Arthrobacter, and Mesorhizobium. The nitrate content was positively correlated with the abundance of Gemmatimonadetes, and the nitrate content was significantly negatively correlated with the relative abundance of Ilumatobacter. Carbohydrate transport and metabolism in the rhizosphere soil of pakchoi decreased, and lipid transport and metabolism increased after biochar application. Conclusion: Overall, our results indicated that applying biochar improved soil physicochemical states and plant nutrient absorption, and affected the abundance of dominant bacterial groups (e.g., Gemmatimonadetes and Ilumatobacter), these were the main factors to increase pakchoi growth and promote quality of pakchoi. Therefore, considering the growth, quality of pakchoi, and soil environment, the effect of using 3% biochar is better.

Chelator Iminodisuccinic Acid Regulates Reactive Oxygen Species Accumulation and Improves Maize (Zea mays L.) Seed Germination under Pb Stress.

To explore the effects of iminodisuccinic acid (a chelating agent) on maize (Zea mays L.) seed germination under lead (Pb) stress, we comparatively analyzed the effects of applying different concentrations of iminodisuccinic acid (0, 5, 20, and 100 mmol·dm-3) and combined an addition of exogenous substances regulating reactive oxygen species production on maize seed germination, seedling growth, H2O2 content, NADPH oxidase activity, and antioxidant enzyme activities under Pb-stressed and Pb-free conditions. Iminodisuccinic acid (100 mmol·dm-3) significantly delayed seed germination under normal germination conditions and alleviated the inhibitory effects of Pb stress (20 mmol·dm-3) on seed germination. Under normal conditions (without Pb stress), the iminodisuccinic acid-induced inhibition of seed germination was enhanced by treatment with dimethylthiourea (a specific scavenger of reactive oxygen species) or diphenyleneiodonium chloride (a specific inhibitor of NADPH oxidase), but diminished by treatment with H2O2, CaCl2, diethyldithiocarbamic acid (a specific inhibitor of superoxide dismutase), or aminotriazole (a specific inhibitor of catalase). Under Pb stress, iminodisuccinic acid partially eliminated the excessive H2O2 accumulation, improved superoxide dismutase and catalase activity, and weakened the high NADPH oxidase activity. In addition, Ca2+ chelation may be essential for maintaining the reactive oxygen species' balance and improving seed germination and seedling growth by iminodisuccinic acid supplementation in maize under Pb stress. The proposed iminodisuccinic acid supplementation-based method improved maize seed germination in Pb-polluted soil.

Pyrite-Based Autotrophic Denitrifying Microorganisms Derived from Paddy Soils: Effects of Organic Co-Substrate Addition.

The presence of organic co-substrate in groundwater and soils is inevitable, and much remains to be learned about the roles of organic co-substrates during pyrite-based denitrification. Herein, an organic co-substrate (acetate) was added to a pyrite-based denitrification system, and the impact of the organic co-substrate on the performance and bacterial community of pyrite-based denitrification processes was evaluated. The addition of organic co-substrate at concentrations higher than 48 mg L-1 inhibited pyrite-based autotrophic denitrification, as no sulfate was produced in treatments with high organic co-substrate addition. In contrast, both competition and promotion effects on pyrite-based autotrophic denitrification occurred with organic co-substrate addition at concentrations of 24 and 48 mg L-1. The subsequent validation experiments suggested that competition had a greater influence than promotion when organic co-substrate was added, even at a low concentration. Thiobacillus, a common chemolithoautotrophic sulfur-oxidizing denitrifier, dominated the system with a relative abundance of 13.04% when pyrite served as the sole electron donor. With the addition of organic co-substrate, Pseudomonas became the dominant genus, with 60.82%, 61.34%, 70.37%, 73.44%, and 35.46% abundance at organic matter concentrations of 24, 48, 120, 240, and 480 mg L-1, respectively. These findings provide an important theoretical basis for the cultivation of pyrite-based autotrophic denitrifying microorganisms for nitrate removal in soils and groundwater.

Single-exposure height-recovery structured illumination microscopy based on deep learning.

Modulation-based structured illumination microscopy (SIM) is performed to reconstruct three-dimensional (3D) surface topography. Generally speaking, modulation decoding algorithms mainly include a phase-shift (PS) method and frequency analysis technique. The PS method requires at least three images with fixed PSs, which leads to low efficiency. Frequency methods could decode modulation from a single image, but the loss of high-frequency information is inevitable. In addition, these methods all need to calculate the mapping relationship between modulation and height to recover the 3D shape. In this paper, we propose a deep learning enabled single-exposure surface measurement method. With only one fringe image, this method can directly restore the height information of the object. Processes such as denoising, modulation calculation, and height mapping are all included in the neural network. Compared with traditional Fourier methods, our method has higher accuracy and efficiency. Experimental results demonstrate that the proposed method can provide accurate and fast surface measurement for different structures.

LightFD: Real-Time Fault Diagnosis with Edge Intelligence for Power Transformers.

Power fault monitoring based on acoustic waves has gained a great deal of attention in industry. Existing methods for fault diagnosis typically collect sound signals on site and transmit them to a back-end server for analysis, which may fail to provide a real-time response due to transmission packet loss and latency. However, the limited computing power of edge devices and the existing methods for feature extraction pose a significant challenge to performing diagnosis on the edge. In this paper, we propose a fast Lightweight Fault Diagnosis method for power transformers, referred to as LightFD, which integrates several technical components. Firstly, before feature extraction, we design an asymmetric Hamming-cosine window function to reduce signal spectrum leakage and ensure data integrity. Secondly, we design a multidimensional spatio-temporal feature extraction method to extract acoustic features. Finally, we design a parallel dual-layer, dual-channel lightweight neural network to realize the classification of different fault types on edge devices with limited computing power. Extensive simulation and experimental results show that the diagnostic precision and recall of LightFD reach 94.64% and 95.33%, which represent an improvement of 4% and 1.6% over the traditional SVM method, respectively.

Klebsiella variicola improves the antioxidant ability of maize seedlings under saline-alkali stress.

BACKGROUND: Saline-alkali soil is mainly distributed in the northern and coastal areas of China. The Songnen Plain, located in the northeast of China, is a region with a relatively high concentration of saline-alkali soil and is also one of the more at-risk areas in the country. Every year, the increasing spread of saline-alkali soil areas has a serious impact on the growth of agricultural crops. The maize crop is sensitive to saline-alkali stress, which seriously affects its growth and development. Our previous study determined that Klebsiella variicola performs a variety of biological functions, as well as improves the rhizosphere microenvironment and promotes the growth and development of maize seedlings in saline-alkali soil environments. The present study further analyzed the mechanism that enables K. variicola to alleviate saline-alkali stress at the level of the antioxidant system. METHODS: The accumulation of O2 - was observed directly via histochemical staining. The activities of several antioxidant enzymes were determined using the nitro blue tetrazolium and the guaiacol methods. The contents of non-enzymatic antioxidants were determined using the dithionitrobenzoic acid method. RESULTS: The contents of the superoxide anion and hydrogen peroxide in leaves and roots of maize seedlings increased under saline-alkali stress conditions. The higher level of reactive oxygen species increased the degree of membrane lipid peroxidation. There were differences in the degree of oxidative damage and performance of the antioxidant defence system in maize seedlings under saline-alkali stress. Following the application of increasing concentrations of K. variicola, the activity of antioxidant enzymes increased by 21.22%-215.46%, and the content of non-enzymatic antioxidants increased as well, the ratios of ASA/DHA and GSH/GSSG in leaves increased by 4.97% and 1.87 times, respectively, and those in roots increased by 3.24% and 1.60 times, respectively. The accumulation of reactive oxygen species was reduced, and the content of H2O2 decreased by 26.07%-46.97%. The content of O2 - decreased by 20.18%-37.01%, which alleviated the oxidative damage to maize seedlings caused by saline-alkali stress. CONCLUSION: K. variicola reduced ROS-induced peroxidation to membrane lipids and effectively alleviated the damage caused by saline-alkali stress by increasing the activities of antioxidant enzymes in maize seedlings, thus enhancing their saline-alkali tolerance. A bacterial concentration of 1×108 cfu/mL was optimal in each set of experiments.

Saline-alkaline stress in growing maize seedlings is alleviated by Trichoderma asperellum through regulation of the soil environment.

A significant proportion of the land area of Heilongjiang Province, China, is composed of saline-alkaline soil, which severely inhibits maize growth. Although Trichoderma treatment is widely regarded as a promising strategy for improving the soil environment and promoting plant growth, the mechanism through which Trichoderma asperellum enhances maize resistance to saline-alkaline stress is not clear. In this study, we explored the effect of T. asperellum application at different concentrations to soil saline-alkaline environment on the seedlings of two maize cultivars, assessing the biochemical parameters related to oxidation resistance. Increasing spore densities of T. asperellum suspension effectively regulated the soil ion balance in the rhizosphere of maize seedlings, reduced the soil pH by 2.15-5.76% and sodium adsorption ratios by 22.70-54.13%, increased soil nutrient content and enzyme activity, and improved the soil environment for seedling growth. Additionally, T. asperellum treatment increased the maize seedling content of osmo-regulating substances and rate of glutathione:oxidised glutathione (43.86-88.25%) and ascorbate:oxidised ascorbate (25.26-222.32%) by affecting the antioxidant enzyme activity in the roots, increasing reactive oxygen species scavenging, and maintaining the osmotic balance and metabolic homeostasis under saline-alkaline stress. T. asperellum also improved the saline-alkaline tolerance of maize seedlings by improving the root growth characteristics. Moreover, results showed that Trichoderma applied at high concentration had the greatest effect. In conclusion, improvement in the saline-alkaline tolerance of maize seedlings by T. asperellum under saline-alkaline soil conditions may be achieved through diverse effects that vary among maize cultivars.

Biological function of Klebsiella variicola and its effect on the rhizosphere soil of maize seedlings.

BACKGROUND: Deterioration of the ecological environment in recent years has led to increasing soil salinization, which severely affects the cultivation of agricultural crops. While research has focused on improving soil environment through the application of pollution-free microbial fertilizers, there are relatively few plant growth-promoting bacteria suitable for saline-alkali environments. Although Klebsiella variicola can adapt to saline-alkali environments to successfully colonize rhizosphere microenvironments, only a few studies have investigated its role in promoting crop growth. Its effect on the crop rhizosphere soil microenvironment is especially unclear. METHODS: In this study, the biological function of K. variicola and its colonization in maize seedling rhizosphere soil were studied in detail through selective media and ultraviolet spectrophotometry. The effects of K. variicola on the rhizosphere soil microenvironment and the growth of maize seedlings in saline-alkali and neutral soils were systematically analysed using the colorimetric method, the potassium dichromate volumetric method, and the diffusion absorption method. RESULTS: Our results showed that K. variicola played a role in indole acetic acid, acetoin, ammonia, phosphorus, and potassium production, as well as in nitrogen fixation. A high level of colonization was observed in the rhizosphere soil of maize seedlings. Following the application of K. variicola in neutral and saline-alkali soils, the nutrient composition of rhizosphere soil of maize seedlings increased in varying degrees, more notably in saline-alkali soil. The content of organic matter, alkali-hydrolysable nitrogen, available phosphorus, available potassium, alkaline phosphatase, sucrase, urease, and catalase increased by 64.22%, 117.39%, 175.64%, 28.63%, 146.08%, 76.77%, 86.60%, and 45.29%, respectively, insaline-alkalisoil. CONCLUSION: K.variicola, therefore, performed a variety of biological functions to promote the growth of maize seedlings and effectively improve the level of soil nutrients and enzymes in the rhizosphere of maize seedlings, undersaline-alkali stress conditions. It played an important role in enhancing the rhizosphere microenvironment of maize seedlings under saline-alkali stress.

Function and Regulation of Ammonium Transporters in Plants.

Ammonium transporter (AMT)-mediated acquisition of ammonium nitrogen from soils is essential for the nitrogen demand of plants, especially for those plants growing in flooded or acidic soils where ammonium is dominant. Recent advances show that AMTs additionally participate in many other physiological processes such as transporting ammonium from symbiotic fungi to plants, transporting ammonium from roots to shoots, transferring ammonium in leaves and reproductive organs, or facilitating resistance to plant diseases via ammonium transport. Besides being a transporter, several AMTs are required for the root development upon ammonium exposure. To avoid the adverse effects of inadequate or excessive intake of ammonium nitrogen on plant growth and development, activities of AMTs are fine-tuned not only at the transcriptional level by the participation of at least four transcription factors, but also at protein level by phosphorylation, pH, endocytosis, and heterotrimerization. Despite these progresses, it is worth noting that stronger growth inhibition, not facilitation, unfortunately occurs when AMT overexpression lines are exposed to optimal or slightly excessive ammonium. This implies that a long road remains towards overcoming potential limiting factors and achieving AMT-facilitated yield increase to accomplish the goal of persistent yield increase under the present high nitrogen input mode in agriculture.

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We examined the effects of a combination of slow-release urea (PCU) and common urea (PU) applied at different soil depths (0-30 cm soil layer) on inorganic nitrogen content, enzyme activity, and crop yield during two years (2017-2018) in a field experiment. There were eight treatments: CK (without N fertilizer); PU1(common urea applied at 5-10 cm deep soil layer); PU2(common urea applied at 5-10 cm deep soil layer, 60% seed fertilizer + 40% topdressing); PU3(20% common urea at 5-10 cm soil depth, 30% common urea at 15-20 cm soil depth, 50% common urea at 25-30 cm soil depth); PCU1(20% total nitrogen application rate at 5-10 cm soil depth, 30% total nitrogen application rate at 15-20 cm soil depth, 50% total nitrogen application rate at 25-30 cm soil depth), the N fertilizer at 5-10 cm was common urea, but, at 15-20 and 25-30 cm, it was a combination of PCU and PU at ratios of 3:7 and 3:7; PCU2 was as PCU1 but the ratio of PCU and PU was 5:5 at 15-20 cm and 5:5 at 25-30 cm; in PCU3, the ratio of PCU and PU was 3:7 at 15-20 cm and 5:5 at 25-30 cm; in PCU4, the ratio of PCU and PU was 5:5 at 15-20 cm and 3:7 at 25-30 cm. The results showed that PU1 could meet nitrogen demand at the 0-10 cm layer in the early growth stage compared with CK. PU2 and PU3 could meet nitrogen demand for 10-30 cm soil layer in the early stage of maize development. The combined application of slow release urea and common urea could meet nitrogen demand for the whole growth period of maize. In the filling and maturing period, combined application of slow release and common urea significantly increased not only NO3--N, NH4+-N, and alkali-hydrolyzed nitrogen contents but also urease and protease activities in the 10-20 cm and 20-30 cm soil layers compared with PU1-PU3. Compared with PU3, maize yield increased by 2.3%-24.6% and 1.3%-16.5% in the PCU1-PCU4 treatments in 2017 and 2018, respectively. PCU4 had the highest yield, with 13899 and 12439 kg·hm-2, respectively. Therefore, the combined application of slow-release and common urea at different soil layers could meet nitrogen demand in the early growth stage of maize and increase the content of inorganic nitrogen and enzyme activities in the 10-30 cm soil layers in the later growth period, which promoted the growth and increased the yield of maize. Among all the treatments PCU4 treatment was the most effective.

Detoxification enzymes associated with butene-fipronil resistance in Epacromius coerulipes.

BACKGROUND: Epacromius coerulipes is a widely distributed locust pest species. Chemical control is the main method used to kill locusts; however, this can result in the selection of locusts with resistance to chemical pesticides. Therefore, the study of resistance is of great significance for the sustainable management of locusts. RESULTS: In this study, to investigate the relationship between detoxification enzymes and butene-fipronil resistance in E. coerulipes, resistant strains of the locust were compared with sensitive strains. The synergism of synergistic agents was significantly enhanced, and the activities of multifunctional oxidase, carboxylesterase, and glutathione sulfur transferase were significantly increased. Transcriptome sequencing revealed 226 detoxification enzyme genes and 23 upregulated genes. Neighbor-joining was used to construct a phylogenetic tree of related gene families, which included 59 P450 genes, 52 carboxylesterases (CarE) genes, and 25 glutathione S-transferase (GST) genes. Reverse transcription polymerase chain reaction (RT-PCR) analysis results of overexpressed genes in the resistant population combined with a phylogenetic tree showed that four P450 genes belonged to the CYP6, CYP4, CYP18 and CYP302 families, two CarE genes belonged to Clade A families, and one GST gene belonged to the Sigma family. These family members were annotated as detoxification enzyme genes of metabolic insecticide in the transcriptome databases. CONCLUSIONS: This study showed that P450, CarE and GST together resulted in moderate resistance to butene-fipronil in locusts. The analysis revealed several overexpressed detoxification enzyme genes that will be the focus of future studies on the mechanism of resistance to butene-fipronil. © 2019 Society of Chemical Industry.

Novel Maize NAC Transcriptional Repressor ZmNAC071 Confers Enhanced Sensitivity to ABA and Osmotic Stress by Downregulating Stress-Responsive Genes in Transgenic Arabidopsis.

NAC TFs play crucial roles in response to abiotic stresses in plants. Here, ZmNAC071 was identified as a nuclear located transcriptional repressor. Overexpression of ZmNAC071 in Arabidopsis enhanced sensitivity of transgenic plants to ABA and osmotic stress. The expression levels of SODs, PODs, P5CSs, and AtMYB61 were inhibited by ZmNAC071, which results in reduced ROS scavenging and proline content, increased ROS level, and water loss. Besides, the expression levels of some ABA or abiotic stress-related genes, like ABIs, RD29A, DREBs, and LEAs were also significantly inhibited by ZmNAC071. Yeast one-hybrid assay demonstrated that ZmNAC071 specifically bound to the cis-acting elements containing CGT[G/A] core sequences in the promoter of stress-related genes, suggesting that ZmNAC071 may participate in the regulation of transcription of these genes through recognizing the core sequences CGT[G/A]. These results will facilitate further studies concerning the cis-elements and downstream genes targeted by ZmNAC071 in maize.

Comparative transcriptome analysis of salt-sensitive and salt-tolerant maize reveals potential mechanisms to enhance salt resistance.

BACKGROUND: Salt stress is a devastating environmental stress that causes plant growth inhibition and yield reduction. OBJECTIVE: The identification of salt-tolerant genes brings hope for the generation of salinity-tolerant crop plants through molecular breeding. METHODS: In this study, one salt-sensitive and one salt-tolerant maize inbred line were screened from 242 maize inbred lines. Reactive oxygen species (ROS)-related enzyme activities were detected and salt-responsive comparative transcriptome analysis was performed for control and 220 mM NaCl treated maize leaves. RESULTS: Salt-tolerant maize inbred line (L87) showed higher ROS-related enzyme (SOD, POD, APX and CAT) activities and accumulated relatively lower levels of ROS under salt stress. Of the total DEGs, 1856 upregulated DEGs were specific to L87, including stress tolerance-related members of the 70kDa family of heat shock proteins (Hsp70s) and aquaporins. The DEGs involved in the abscisic acid (ABA), ethylene, jasmonic acid (JA) and salicylic acid (SA) signal transduction pathways may determine the difference in salt tolerance between the two varieties, especially one central component SnRK2, that positively regulates ABA signaling and was only upregulated in L87. Analysis of DEGs related to ROS scavenging showed that some peroxidase (POD), glutathione S-transferase (GST), catalase (CAT) and superoxide dismutase (SOD) genes specific to L87 probably enhanced its salt tolerance. The analysis of differentially expressed transcription factors (TFs) suggested that WRKY TFs could contribute to the difference in salt tolerance between the two maize lines. CONCLUSION: Compared with Salt-sensitive maize inbred line (L29), L87 exhibits specific regulatory mechanisms related to salt tolerance, including plant hormone interactions, ROS scavenging and the regulation of TFs. Our study identifies new candidate genes that may regulate maize tolerance to salt stress and provides useful information for breeding maize with high salt resistance.

Transcription Factor ANAC074 Binds to NRS1, NRS2, or MybSt1 Element in Addition to the NACRS to Regulate Gene Expression.

NAC (NAM, ATAF1/2, and CUC2) transcription factors play important roles in many biological processes, and mainly bind to the NACRS with core sequences "CACG" or "CATGTG" to regulate gene expression. However, whether NAC proteins can bind to other motifs without these core sequences remains unknown. In this study, we employed a Transcription Factor-Centered Yeast one Hybrid (TF-Centered Y1H) screen to study the motifs recognized by ANAC074. In addition to the NACRS core cis-element, we identified that ANAC074 could bind to MybSt1, NRS1, and NRS2. Y1H and GUS assays showed that ANAC074 could bind the promoters of ethylene responsive genes and stress responsive genes via the NRS1, NRS2, or MybSt1 element. ChIP study further confirmed that the bindings of ANAC074 to MybSt1, NRS1, and NRS2 actually occurred in Arabidopsis. Furthermore, ten NAC proteins from different NAC subfamilies in Arabidopsis thaliana were selected and confirmed to bind to the MybSt1, NRS1, and NRS2 motifs, indicating that they are recognized commonly by NACs. These findings will help us to further reveal the functions of NAC proteins.

Omethoate treatment mitigates high salt stress inhibited maize seed germination.

Omethoate (OM) is a highly toxic organophophate insecticide, which is resistant to biodegradation in the environment and is widely used for pest control in agriculture. The effect of OM on maize seed germination was evaluated under salt stress. Salt (800mM) greatly reduced germination of maize seed and this could be reversed by OM. Additionally, H2O2 treatment further improved the effect of OM on seed germination. Higher H2O2 content was measured in OM treated seed compared to those with salt stress alone. Dimethylthiourea (DTMU), a specific scavenger of reactive oxygen species (ROS), inhibited the effect of OM on seed germination, as did IMZ (imidazole), an inhibitor of NADPH oxidase. Abscisic acid (ABA) inhibited the effect of OM on seed germination, whereas fluridone, a specific inhibitor of ABA biosynthesis, enhanced the effect of OM. Taken together, these findings suggest a role of ROS and ABA in the promotion of maize seed germination by OM under salt stress.

Biochemical and Transcriptional Regulation of Membrane Lipid Metabolism in Maize Leaves under Low Temperature.

Membrane lipid modulation is one of the major strategies plants have developed for cold acclimation. In this study, a combined lipidomic and transcriptomic analysis was conducted, and the changes in glycerolipids contents and species, and transcriptional regulation of lipid metabolism in maize leaves under low temperature treatment (5°C) were investigated. The lipidomic analysis showed an increase in the phospholipid phosphatidic acid (PA) and a decrease in phosphatidylcholine (PC). And an increase in digalactosyldiacylglycerol and a decrease in monogalactosyldiacylglycerol of the galactolipid class. The results implied an enhanced turnover of PC to PA to serve as precursors for galactolipid synthesis under following low temperature treatment. The analysis of changes in abundance of various lipid molecular species suggested major alterations of different pathways of plastidic lipids synthesis in maize under cold treatment. The synchronous transcriptomic analysis revealed that genes involved in phospholipid and galactolipid synthesis pathways were significantly up-regulated, and a comprehensive gene-metabolite network was generated illustrating activated membrane lipids adjustment in maize leaves following cold treatment. This study will help to understand the regulation of glycerolipids metabolism at both biochemical and molecular biological levels in 18:3 plants and to decipher the roles played by lipid remodeling in cold response in major field crop maize.

Can antioxidant's reactive oxygen species (ROS) scavenging capacity contribute to aged seed recovery? Contrasting effect of melatonin, ascorbate and glutathione on germination ability of aged maize seeds.

It is well known that antioxidants such as AA (reduced ascorbate), glutathione (GSH) (reduced glutathione) and melatonin can delay seed ageing. Can they recover aged seed? Artificial aged maize seeds were obtained and their reduced germination rate (GR) and high lipid peroxidation were recorded. Exogenous melatonin was applied on these aged seeds and enhanced GR was observed. However, treatment with other antioxidants such as AA, GSH or DMTU (dimethyl thiourea) did not significantly improve or even reduce the GR of aged seeds. In addition, melatonin improved germination ability of theses aged seeds can be significantly impaired by DDC (diethyldithiocarbamic acid, a specific inhibitor of superoxide dismutase or superoxide dismutase (SOD)) and ATZ (aminotriazol, a specific inhibitor of catalase or CAT). In a further study, we found that melatonin but not other antioxidants (AA, GSH and DMTU) significantly induced CAT and SOD activities of aged seeds after imbibition. Accordingly, melatonin significantly reduced lipid peroxidation in aged seeds than that of other antioxidants. Taken together, these data suggest that melatonin induced antioxidant enzyme but not its direct reactive oxygen species (ROS) scavenging capacity contributing to recovery of aged maize seeds.