GWAS across multiple environments and WGCNA suggest the involvement of ZmARF23 in embryonic callus induction from immature maize embryos.

KEY MESSAGE: Combined GWAS, WGCNA, and gene-based association studies identified the co-expression network and hub genes for maize EC induction. ZmARF23 bound to ZmSAUR15 promoter and regulated its expression, affecting EC induction. Embryonic callus (EC) induction in immature maize embryos shows high genotype dependence, which limits the application of genetic transformation in transgenic breeding and gene function elucidation in maize. Herein, we conducted a genome-wide association mapping (GWAS) for four EC induction-related traits, namely rate of embryonic callus induction (REC), increased callus diameter (ICD), ratio of shoot formation (RSF), and length of shoot (LS) across different environments. A total of 77 SNPs were significantly associated these traits under three environments and using the averages (across environments). Among these significant SNPs, five were simultaneously detected under multiple environments and 11 had respective phenotypic variation explained > 10%. A total of 257 genes were located in the linkage disequilibrium decay of these REC- and ICD-associated SNPs, of which 178 were responsive to EC induction. According to the expression values of the 178 genes, we performed a weighted gene co-expression network analysis (WGCNA) and revealed an EC induction-associated module and five hub genes. Hub gene-based association studies uncovered that the intragenic variations in GRMZM2G105473 and ZmARF23 influenced EC induction efficiency among different maize lines. Dual-luciferase reporter assay indicated that ZmARF23 bound to the promoter of a known causal gene (ZmSAUR15) for EC induction and positively regulated its expression on the transcription level. Our study will deepen the understanding of genetic and molecular mechanisms underlying EC induction and contribute to the use of genetic transformation in maize.

Overexpression of ZmSTOP1-A Enhances Aluminum Tolerance in Arabidopsis by Stimulating Organic Acid Secretion and Reactive Oxygen Species Scavenging.

Aluminum (Al) toxicity and low pH are major factors limiting plant growth in acidic soils. Sensitive to Proton Rhizotoxicity 1 (STOP1) transcription factors respond to these stresses by regulating the expression of multiple Al- or low pH-responsive genes. ZmSTOP1-A, a STOP1-like protein from maize (Zea mays), was localized to the nucleus and showed transactivation activity. ZmSTOP1-A was expressed moderately in both roots and shoots of maize seedlings, but was not induced by Al stress or low pH. Overexpression of ZmSTOP1-A in Arabidopsis Atstop1 mutant partially restored Al tolerance and improved low pH tolerance with respect to root growth. Regarding Al tolerance, ZmSTOP1-A/Atstop1 plants showed clear upregulation of organic acid transporter genes, leading to increased organic acid secretion and reduced Al accumulation in roots. In addition, the antioxidant enzyme activity in roots and shoots of ZmSTOP1-A/Atstop1 plants was significantly enhanced, ultimately alleviating Al toxicity via scavenging reactive oxygen species. Similarly, ZmSTOP1-A could directly activate ZmMATE1 expression in maize, positively correlated with the number of Al-responsive GGNVS cis-elements in the ZmMATE1 promoter. Our results reveal that ZmSTOP1-A is an important transcription factor conferring Al tolerance by enhancing organic acid secretion and reactive oxygen species scavenging in Arabidopsis.

ZmNRAMP4 Enhances the Tolerance to Aluminum Stress in Arabidopsis thaliana.

Aluminum (Al) toxicity causes severe reduction in crop yields in acidic soil. The natural resistance-associated macrophage proteins (NRAMPs) play an important role in the transport of mineral elements in plants. Recently, OsNrat1 and SbNrat1 were reported specifically to transport trivalent Al ions. In this study, we functionally characterized ZmNRAMP4, a gene previously identified from RNA-Seq data from Al-treated maize roots, in response to Al exposure in maize. ZmNRAMP4 was predominantly expressed in root tips and was specifically induced by Al stress. Yeast cells expressing ZmNRAMP4 were hypersensitive to Al, which was associated with Al accumulation in yeast. Furthermore, overexpression of ZmNRAMP4 in Arabidopsis conferred transgenic plants with a significant increase in Al tolerance. However, expression of ZmNRAMP4, either in yeast or in Arabidopsis, had no effect on the response to cadmium stress. Taken together, these results underlined an internal tolerance mechanism involving ZmNRAMP4 to enhance Al tolerance via cytoplasmic sequestration of Al in maize.

Overexpression of the Aldehyde Dehydrogenase Gene ZmALDH Confers Aluminum Tolerance in Arabidopsis thaliana.

Aluminum (Al) toxicity is the main factor limiting plant growth and the yield of cereal crops in acidic soils. Al-induced oxidative stress could lead to the excessive accumulation of reactive oxygen species (ROS) and aldehydes in plants. Aldehyde dehydrogenase (ALDH) genes, which play an important role in detoxification of aldehydes when exposed to abiotic stress, have been identified in most species. However, little is known about the function of this gene family in the response to Al stress. Here, we identified an ALDH gene in maize, ZmALDH, involved in protection against Al-induced oxidative stress. Al stress up-regulated ZmALDH expression in both the roots and leaves. The expression of ZmALDH only responded to Al toxicity but not to other stresses including low pH and other metals. The heterologous overexpression of ZmALDH in Arabidopsis increased Al tolerance by promoting the ascorbate-glutathione cycle, increasing the transcript levels of antioxidant enzyme genes as well as the activities of their products, reducing MDA, and increasing free proline synthesis. The overexpression of ZmALDH also reduced Al accumulation in roots. Taken together, these findings suggest that ZmALDH participates in Al-induced oxidative stress and Al accumulation in roots, conferring Al tolerance in transgenic Arabidopsis.

Transcriptomic and genome-wide association study reveal long noncoding RNAs responding to nitrogen deficiency in maize.

BACKGROUND: Long noncoding RNAs (lncRNAs) play important roles in essential biological processes. However, our understanding of lncRNAs as competing endogenous RNAs (ceRNAs) and their responses to nitrogen stress is still limited. RESULTS: Here, we surveyed the lncRNAs and miRNAs in maize inbred line P178 leaves and roots at the seedling stage under high-nitrogen (HN) and low-nitrogen (LN) conditions using lncRNA-Seq and small RNA-Seq. A total of 894 differentially expressed lncRNAs and 38 different miRNAs were identified. Co-expression analysis found that two lncRNAs and four lncRNA-targets could competitively combine with ZmmiR159 and ZmmiR164, respectively. To dissect the genetic regulatory by which lncRNAs might enable adaptation to limited nitrogen availability, an association mapping panel containing a high-density single-nucleotide polymorphism (SNP) array (56,110 SNPs) combined with variable LN tolerant-related phenotypes obtained from hydroponics was used for a genome-wide association study (GWAS). By combining GWAS and RNA-Seq, 170 differently expressed lncRNAs within the range of significant markers were screened. Moreover, 40 consistently LN-responsive genes including those involved in glutamine biosynthesis and nitrogen acquisition in root were identified. Transient expression assays in Nicotiana benthamiana demonstrated that LNC_002923 could inhabit ZmmiR159-guided cleavage of Zm00001d015521. CONCLUSIONS: These lncRNAs containing trait-associated significant SNPs could consider to be related to root development and nutrient utilization. Taken together, the results of our study can provide new insights into the potential regulatory roles of lncRNAs in response to LN stress, and give valuable information for further screening of candidates as well as the improvement of maize resistance to LN stress.

Metabolite profiling and genome-wide association studies reveal response mechanisms of phosphorus deficiency in maize seedling.

Inorganic phosphorus (Pi) is an essential element in numerous metabolic reactions and signaling pathways, but the molecular details of these pathways remain largely unknown. In this study, metabolite profiles of maize (Zea mays L.) leaves and roots were compared between six low-Pi-sensitive lines and six low-Pi-tolerant lines under Pi-sufficient and Pi-deficient conditions to identify pathways and genes associated with the low-Pi stress response. Results showed that under Pi deprivation the concentrations of nucleic acids, organic acids and sugars were increased, but that the concentrations of phosphorylated metabolites, certain amino acids, lipid metabolites and nitrogenous compounds were decreased. The levels of secondary metabolites involved in plant immune reactions, including benzoxazinoids and flavonoids, were significantly different in plants grown under Pi-deficient conditions. Among them, the 11 most stable metabolites showed significant differences under low- and normal-Pi conditions based on the coefficient of variation (CV). Isoleucine and alanine were the most stable metabolites for the identification of Pi-sensitive and Pi-resistant maize inbred lines. With the significant correlation between morphological traits and metabolites, five low-Pi-responding consensus genes associated with morphological traits and simultaneously involved in metabolic pathways were mined by combining metabolites profiles and genome-wide association study (GWAS). The consensus genes induced by Pi deficiency in maize seedlings were also validated by reverse-transcription quantitative polymerase chain reaction (RT-qPCR). Moreover, these genes were further validated in a recombinant inbred line (RIL) population, in which the glucose-6-phosphate-1-epimerase encoding gene mediated yield and correlated traits to phosphorus availability. Together, our results provide a framework for understanding the metabolic processes underlying Pi-deficient responses and give multiple insights into improving the efficiency of Pi use in maize.

Development of a handheld dual-channel optical fiber fluorescence sensor based on a smartphone.

In order to meet the needs of on-site, accurate, fast, and remote detection, we design a smartphone-based handheld dual-channel optical fiber fluorescence sensor (DOFFS), which is composed of a semiconductor laser for exciting fluorescence signals, a smartphone with a dual-bandpass filter for collecting fluorescence signals, a fiber coupler for transmitting light, and batteries for laser power supply. All the components are integrated into a 3D printed shell, on the side of which there are two fiber flanges used for fiber probe connection. The fluorescence signals of green and red quantum dots modified on the fiber probes can be captured by the smartphone camera and calculated by a self-developed Android application. The comparisons of single-channel and dual-channel fluorescence signals with pH show that the performance of the sensor is good. The proposed sensor not only can simultaneously detect dual-channel signals for fast detection needs, but it also is handheld with a small size of 79×57×154mm3 and inner power supply, and the fiber probes can be easily replaced, supporting remote and on-site applications. It is a potential tool for many occasions in many fields.

Comparative transcriptome analysis reveals that tricarboxylic acid cycle-related genes are associated with maize CMS-C fertility restoration.

BACKGROUND: C-type cytoplasmic male sterility (CMS-C) is one of the three major types of cytoplasmic male sterility (CMS) in maize. Rf4 is a dominant restorer gene for CMS-C and has great value in hybrid maize breeding, but little information concerning its functional mechanism is known. RESULTS: To reveal the functional mechanism of Rf4, we developed a pair of maize near-isogenic lines (NILs) for the Rf4 locus, which included a NIL_rf4 male-sterile line and a NIL_Rf4 male fertility-restored line. Genetic analysis and molecular marker detection indicated that the male fertility of NIL_Rf4 was controlled by Rf4. Whole-genome sequencing demonstrated genomic differences between the two NILs was clustered in the Rf4 mapping region. Unmapped reads of NILs were further assembled to uncover Rf4 candidates. RNA-Seq was then performed for the developing anthers of the NILs to identify critical genes and pathways associated with fertility restoration. A total of 7125 differentially expressed genes (DEGs) were identified. These DEGs were significantly enriched in 242 Gene Ontology (GO) categories, wherein 100 DEGs were involved in pollen tube development, pollen tube growth, pollen development, and gametophyte development. Homology analysis revealed 198 male fertility-related DEGs, and pathway enrichment analysis revealed that 58 DEGs were enriched in cell energy metabolism processes involved in glycolysis, the pentose phosphate pathway, and pyruvate metabolism. By querying the Plant Reactome Pathway database, we found that 14 of the DEGs were involved in the mitochondrial tricarboxylic acid (TCA) cycle and that most of them belonged to the isocitrate dehydrogenase (IDH) and oxoglutarate dehydrogenase (OGDH) enzyme complexes. Transcriptome sequencing and real-time quantitative PCR (qPCR) showed that all the above TCA cycle-related genes were up-regulated in NIL_Rf4. The results of our subsequent enzyme-linked immunosorbent assay (ELISA) experiments pointed out that the contents of both the IDH and OGDH enzymes accumulated more in the spikelets of NIL_Rf4 than in those of NIL_rf4. CONCLUSION: The present research provides valuable genomic resources for deep insight into the molecular mechanism underlying CMS-C male fertility restoration. Importantly, our results indicated that genes involved in energy metabolism, especially some mitochondrial TCA cycle-related genes, were associated with maize CMS-C male fertility restoration.

The maize CorA/MRS2/MGT-type Mg transporter, ZmMGT10, responses to magnesium deficiency and confers low magnesium tolerance in transgenic Arabidopsis.

KEY MESSAGE: ZmMGT10 was specifically expressed in maize roots and induced by a deficiency of magnesium. Overexpression of ZmMGT10 restored growth deficiency of the Salmonella typhimurium MM281 strain and enhanced the tolerance in Arabidopsis to stress induced by low magnesium levels by increasing uptake of Mg2+ via roots. CorA/MRS2/MGT-type Mg2+ transporters play a significant role in maintaining magnesium (Mg) homeostasis in plants. Although the maize CorA/MRS2/MGT family comprises of 12 members, currently no member has been functionally characterized. Here, we report the isolation and functional characterization of ZmMGT10 from the maize MRS2/MGT gene family. ZmMGT10 has a typical structure feature which includes two conserved TMs near the C-terminal end and an altered AMN tripeptide motif. The high sequence similarity and close phylogenetic relationship indicates that ZmMGT10 is probably the counterpart of Arabidopsis AtMGT6. The complementation of the Salmonella typhimurium mutated MM281 strain indicates that ZmMGT10 possesses the ability to transport Mg2+. ZmMGT10 was specifically expressed in the plant roots and it can be stimulated by a deficiency of Mg. Transgenic Arabidopsis plants which overexpressed ZmMGT10 grew more vigorously than wild-type plants under low Mg conditions, exhibited by longer root length, higher plant fresh weight and chlorophyll content, suggesting ZmMGT10 was essential for plant growth and development under low Mg conditions. Further investigations found that high accumulation of Mg2+ occurred in transgenic plants attributed to improved Mg2+ uptake and thereby enhanced tolerance to Mg deficiency. Results from this investigation illustrate that ZmMGT10 is a Mg transporter of maize which can enhance the tolerance to Mg deficient conditions by improving Mg2+ uptake in the transgenic plants of Arabidopsis.

Identification, and Functional and Expression Analyses of the CorA/MRS2/MGT-Type Magnesium Transporter Family in Maize.

Magnesium (Mg(2+)) is an essential macronutrient for plant growth and development, and the CorA/MRS2/MGT-type Mg(2+) transporters play important roles in maintaining Mg(2+) homeostasis in plants. Although the MRS2/MGT genes have been identified in two model plant species, Arabidopsis and rice, a comprehensive analysis of the MRS2/MGT gene family in other plants is lacking. In this work, 12 putative MRS2/MGT genes (ZmMGT1- ZmMGT12) were identified in maize and all of them were classified into five distinct subfamilies by phylogenetic analysis. A complementation assay in the Salmonella typhimurium MM281 strain showed that five representatives of the 12 members possess Mg(2+) transport abilities. Inhibition of ZmMGT protein activity using the hexaamminecobalt (III) (Co-Hex) inhibitor indicated that the ZmMGT protein mediated both low-affinity and high-affinity Mg(2+) transport in maize. A semi-quantitative reverse transcription-PCR (RT-PCR) analysis revealed that eight genes were constitutively expressed in all of the detected tissues, with one being specifically expressed in roots and three having no detectable expression signals. A quantitative RT-PCR analysis showed that some ZmMGT members displayed differential responses to Mg(2+) deficiency and aluminum (Al) stress. Furthermore, root growth inhibition and Mg(2+) accumulation analyses in two maize inbred lines, which conferred different levels of Al tolerance, revealed that ZmMGT proteins contributed to the Al resistance of the Al tolerance genotype. We hypothesize that ZmMGT family members function as Mg(2+) transporters and may play a role in linking Mg(2+) deficiency and Al stress responses. Our results will be valuable in a further analysis of the important biological functions of ZmMGT members in maize.

Genome-wide identification of microRNAs responding to early stages of phosphate deficiency in maize.

Phosphorus (P) is an essential element involved in numerous biochemical reactions. In plants, stress responses, such as the expression of microRNAs (miRNAs), are induced to help them adapt to low phosphate (Pi) concentrations. In this study, deep sequencing was performed using the roots and leaves of maize seedlings grown under low Pi concentrations to identify miRNAs that are differentially expressed during the early stages of Pi deficiency. Eight small RNA libraries were constructed, and 159 known miRNAs representing 32 miRNA families and 10 novel miRNAs. Members of the miR396 family were extremely abundant. Further, 28 Pi-responsive miRNAs were identified (27 known and 1 novel) of which 8 and 7 were significantly expressed exclusively in leaf and root tissues, respectively. The analysis of Pi-responsive miRNAs target genes suggested that most target genes functioning as transcription factors were involved in root and leaf development. The expression profiles of selected Pi-responsive miRNAs and target genes were confirmed by quantitative real-time polymerase chain reaction (qRT-PCR). Moreover, we discuss the significance of the differences in expression patterns of these miRNAs during the early and later stages of Pi starvation. This study provides useful information concerning the role of miRNAs in response to Pi starvation and will further our understanding of the mechanisms governing Pi homeostasis in maize.

[Cloning and functional validation of promoter of mo-molybdopterin cofactor sulfurase gene in maize].

To overcome the problems caused by the over-expression of exogenous genes under the control of constitutive promoters, the promoter (ABA3s) sequence of maize (Zea mays) mo-molybdopterin cofactor sulfurase gene (ABA3) was cloned homologously, analyzed for its abiotic stress-responsive elements by the PlantCARE software, and detected for differential expression of the ABA3 gene under the abiotic stresses by real-time quantitative PCR. Then, this promoter was used to construct expression vector to start GUS (ß-glucuronidase) gene, and transform maize calli by biolistics. After identification by histochemical staining, the ratio of the GUS activity relative to the luciferase activity (internal control) (GUS/LUC) was measured under the stresses of hypertonic, high salt, low temperature, and the induction of ABA, and used to evaluate the activity of the ABA3s promoter in response to abiotic stresses. The results showed that the ABA3 gene was differentially expressed under the stress of simulative drought, low temperature, high temperature, high salt, and the induction of ABA and ethylene, indicating that the promoter (ABA3s) of this gene is induced by abtiotic stress. The sequence analysis showed that the ABA3s promoter is 777 bp long, and contains abiotic stress-responsive elements ARE, HSE, MBS, TGA and circadian. The transformed calli by the expression vector of the GUS gene under the control of the ABA3s promoter showed positive in GUS detection in response to the abiotic stresses of drought, low temperature, high temperature, high salt, and the induction of ABA and ethylene. The GUS/LUC ratio was six folds higher than the blank control under the hypertonic stress of 8% mannitol. It is concluded that the promoter ABA3s is inducible in response to abiotic stresses, and might be applied to transgenic research of maize for abiotic tolerance after further functional evaluation.

The Effect of Granulocyte Colony-Stimulating Factor on Endometrial Receptivity of Implantation Failure Mouse.

The purpose of this study was to investigate the effect of G-CSF on the endometrial receptivity of implantation failure mice. Sixty female mice were treated mifepristone to establish an implant failure model. The treatment groups received different doses of G-CSF. Endometrial tissue and serum were collected on day 5 after mating. The abundance of pinopodes on the endometrium was observed by scanning electron microscopy. The expressions of LPAR3, COX2, and HOXA10 were detected by RT-qPCR and Western blotting. Serum levels of E2, P, VEGF, LIF, TNF-α and IL-10 were measured by ELISA. The expressions of VEGF, CD34, CD57, TNF-α, and IL-10 were assessed by immunohistochemistry. Immunofluorescence analysis was performed to determine the number of CD57, Treg, and Th17 cells. G-CSF increased implantation and pregnancy rates of mifepristone-induced implantation failure mice, with the most significant effect seen at the intermediate dose. G-CSF increased the serum levels of E2 and P, the abundance of endometrial pinopodes, and the level of LIF in the endometrium. It also promoted the expression of VEGF, HOXA10, LPAR3, and COX2. Moreover, G-CSF reduced the level of CD57 cells and the ratio of Th17/Treg cells in endometrium. G-CSF reduced the inflammatory factor TNF-α, but IL-10 did not change significantly. G-CSF can enhance embryo implantation rate and pregnancy rate and improve endometrial receptivity by attenuating degeneration of pinopodes, upregulating estrogen and progesterone, facilitating angiogenesis, maintaining immune cell homeostasis, and reducing the production of inflammatory cytokines in implantation failure mouse.

Genome expression profile analysis reveals important transcripts in maize roots responding to the stress of heavy metal Pb.

Lead (Pb) has become one of the most abundant heavy metal pollutants of the environment. With its large biomass, maize could be an important object for studying the phytoremediation of Pb-contaminated soil. In our previous research, we screened 19 inbred lines of maize for Pb concentration, and line 178 was identified to be a hyperaccumulator for Pb in both the roots and aboveground parts. To identify important genes and metabolic pathways related to Pb accumulation and tolerance, line 178 was underwent genome expression profile under Pb stress and a control (CK). A total of approximately 11 million cDNA tags were sequenced and 4 665 539 and 4 936 038 clean tags were obtained from the libraries of the test and CK, respectively. In comparison to CK, 2379 and 1832 genes were identified up- or downregulated, respectively, more than fivefolds under Pb stress. Interestingly, all the genes were related to cellular processes and signaling, information storage and processing or metabolism functions. Particularly, the genes involved in posttranslational modification, protein turnover and chaperones; signal transduction, carbohydrate transport and metabolism; and lipid transport and metabolism significantly changed under the treatment. In addition, seven pathways including ribosome, photosynthesis, and carbon fixation were affected significantly, with 118, 12, 34, 21, 18, 72 and 43 differentially expressed genes involved. The significant upregulation of the ribosome pathway may reveal an important secret for Pb tolerance of line 178. And the sharp increase of laccase transcripts and metal ion transporters were suggested to account in part for Pb hyperaccumulation in the line.

The protective effect of total glucosides of white paeony capsules on experimental autoimmune encephalomyelitis.

AIMS: To learn about the effect and mechanism of total glucosides of white peony capsule (TGP), on experimental autoimmune encephalomyelitis (EAE), an acknowledged animal model of multiple sclerosis (MS). METHODS: The rat model of EAE was induced by subcutaneous injection with guinea pig spinal cord homogenate. The severity of the disease model was assessed by clinical score, hematoxylin and eosin (H&E) and luxol fast blue (LFB). Immunohistochemical assay was used to observe the types of inflammatory cells and adhesive molecule expression. Enzyme-linked immunosorbent assay (ELISA) was applied to detect content of the stem cell growth factor / mast cell growth factor (scf/MGF), interleukin-6 (IL-6) and IL-2. Immunofluorescence assay was applied to observe the expression of connexin43 (Cx43), glial fibrillary acidic protein (GFAP), connexin47 (Cx47) and the monoclonal antibody anti-adenomatous polyposis coli (APC) clone CC1. RESULTS: Compare with the animals in EAE model group, TGP treated rats (particularly those treated with high doses) showed a significant decrease in morbidity, clinical scores, CNS infiltration of inflammatory cells (including mononuclear macrophages, CD4+ and CD8+ T cells) and demyelination. The key adhesion molecule ICAM-1, cytokines IL-2、IL-6 and scf/MGF were significantly decreased with TGP treatment. Oppositely, PD-1, connexin47 in oligodendrocytes and connexin43 in astrocytes were elevated with TGP treatment. CONCLUSION: To sum up, TGP exhibited a significantly prevention and treatment effect on EAE rat model, and this improvement was achieved through a combination way composed of glial and inflammatory cells, junction proteins, various factors including adhesion factors, interleukins and scf/MGF.

Analgesics can affect the sensitivity of temozolomide to glioma chemotherapy through gap junction.

This study investigated the effect of frequently used analgesics in cancer pain management (flurbiprofen (FLU), tramadol (TRA), and morphine (MOR)) and a novel α2-adrenergic agonist (dexmedetomidine, DEX) on temozolomide (TMZ) sensitivity in glioma cells. Cell counting kit-8 and colony-formation assays were performed to analyze the viability of U87 and SHG-44 cell lines. A high and low cell density of colony method, pharmacological methods, and connexin43 mimetic peptide GAP27 were used to manipulate the function of gap junctions; "Parachute" dye coupling and western blot were employed to determine junctional channel transfer ability and connexin expression. The results showed that DEX (in the concentration range of 0.1 to 5.0 ng/ml) and TRA (in the concentration range of 1.0 to 10.0 µg/ml) reduced the TMZ cytotoxicity in a concentration-dependent manner but was only observed with high cell density (having formed gap junction). The cell viability percentage was 71.3 to 86.8% when DEX was applied at 5.0 ng/ml, while tramadol showed 69.6 to 83.7% viability at 5.0 µg/ml in U87 cells. Similarly, 5.0 ng/ml of DEX resulted in 62.6 to 80.5%, and 5.0 µg/ml TRA showed 63.5 to 77.3% viability in SHG-44 cells. Further investigating the impact of analgesics on gap junctions, only DEX and TRA were found to decrease channel dye transfer through connexin phosphorylation and ERK pathway, while no such effect was observed for FLU and MOR. Analgesics that can affect junctional communication may compromise the effectiveness of TMZ when used simultaneously.

Monocyte-endothelial adhesion is modulated by Cx43-stimulated ATP release from monocytes.

Adhesion of circulating monocytes to vascular endothelial cells is a crucial event in development of vascular inflammatory conditions, including atherosclerosis. We investigated the roles of connexin43 (Cx43) and ATP release on monocyte-endothelial adhesion. Cx43 function and expression were manipulated by connexin channel inhibitors, overexpression and siRNA. Connexin channel inhibitors rapidly decreased ATP release from U937 monocytes and increased adhesion to human umbilical vein endothelial cells (HUVEC). Monocyte ATP release correlated with Cx43 expression, not with Cx37 expression. Exogenous adenosine (ADO) or ATP decreased adhesion, and inhibition of ATP conversion to ADO increased adhesion. We infer that monocyte Cx43 channel activity causes ATP release, likely via Cx43-containing hemichannels, and that ATP decreases adhesion via conversion to ADO. Inhibition of HUVEC connexin channel activity did not affect ATP release or adhesion. In contrast, expression of Cx43 protein in U937 cells enhanced adhesion. Thus, Cx43 channel function and expression have opposite effects: Cx43 channel function in monocytes, but not in HUVEC, rapidly decreases adhesion via ATP release and conversion to ADO, whereas Cx43 expression itself enhances adhesion. These studies suggest that local regulation of monocyte Cx43 activity within the vasculature can dynamically modulate the monocyte-endothelial adhesion that is an initiating event in vascular inflammatory pathologies, with the baseline adhesion set by Cx43 expression levels. This balance of rapid and tonic influences may be crucial in development of vascular pathologies.

Adsorption and desorption of herbicide monosulfuron-ester in Chinese soils.

Monosulfuron-ester is a new, low rate, sulfonylurea herbicide that is being promoted for annual broadleaf and gramineal weed control; however, there is a lack of published information on its behavior in soils. The adsorption and desorption of monosulfuron-ester by seven type soils were measured using a batch equilibrium technique. The results showed that the Freundlich equation fitted its adsorption and desorption well, and the Freundlich constant values (K(f-ads)) ranged from 0.88 to 5.66. Adsorption isotherms were nonlinear with 1/n(f-ads) values < 1. Soil pH, organic matter (OM), and clay content were the main factors influencing its adsorption and desorption. Adsorption and desorption were negatively correlated with pH 4.0-8.0 while positively correlated with OM and clay content. The adsorption of monosulfuron-ester was mainly a physical process, because its free energy (deltaG) in seven soils was less than 40 kJ/mol. Monosulfuron-ester adsorption by three soils increased with increasing CaCl2 concentration using CaCl2 as a background electrolyte. Monosulfuron-ester desorption was hysteretic in all tested soils.

ZmXTH, a xyloglucan endotransglucosylase/hydrolase gene of maize, conferred aluminum tolerance in Arabidopsis.

Aluminum (Al) toxicity is one of the primary factors limiting crop production in acid soils worldwide. The cell wall is the major target of Al toxicity owing to the presence of many Al binding sites. Previous studies have found that XTH, encoding xyloglucan endohydrolase (XEH) and xyloglucan endotransglucosylase (XET), could participate in cell wall extension and affect the binding ability of the cell wall to Al by impeding the activities of these two enzymes. In this study, we found that ZmXTH, an XTH gene in maize, was involved in Al detoxification. The Al-induced up-regulation of ZmXTH occurred in the roots, prominently in the root tips. Additionally, the expression of ZmXTH was specifically induced by Al3+ but no other divalent or trivalent cations. Compared with the wild-type Arabidopsis, ZmXTH overexpressing plants grew more healthy and had decreased Al content in their root and root cell wall after Al stress. Overall, the results suggest that ZmXTH could confer the Al tolerance of transgenic Arabidopsis plants by reducing the Al accumulation in their roots and cell walls.

ZmMATE6 from maize encodes a citrate transporter that enhances aluminum tolerance in transgenic Arabidopsis thaliana.

The yields of cereal crops grown on acidic soils are often reduced by aluminum (Al) toxicity because the prevalence of toxic Al3+ cations increases as pH falls below 5.0. The Al-dependent release of citrate from resistant lines of maize is controlled by ZmMATE1 which encodes a multidrug and toxic compound extrusion (MATE) transporter protein. ZmMATE6 is another member of this family in maize whose expression is also increased by Al treatment. We investigated the function of this gene in more detail to determine whether it also contributes to Al resistance. Quantitative RT-PCR measurements found that ZmMATE6 was expressed in the roots and leaves of Al-resistant and sensitive inbred lines. Treatment with Al induced ZmMATE6 expression in all tissues but several other divalent or trivalent cations tested had no effect on expression. This expression pattern and the induction by Al treatment was confirmed in ZmMATE6 promoter-ß-glucuronidase fusion lines. Heterogeneous expression of ZmMATE6 displayed a greater Al-activated release of citrate from the roots and was significantly resistant to Al toxicity than controls. This was associated with reduced accumulation of Al in the root tissues. Our results demonstrated that ZmMATE6 expression is induced by Al and functions as a citrate transporter.