27 research outputs found

    Table_1.PDF

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    <p>Sulfite oxidase (SO) plays a pivotal role in sulfite metabolism. In our previous study, sulfite-oxidizing function of the SO from Zea mays (ZmSO) was characterized. To date, the knowledge of ZmSO’s involvement in abiotic stress response is scarce. In this study, we aimed to investigate the role of ZmSO in drought stress. The transcript levels of ZmSO were relatively high in leaves and immature embryos of maize plants, and were up-regulated markedly by PEG-induced water stress. Overexpression of ZmSO improved drought tolerance in tobacco. ZmSO-overexpressing transgenic plants showed higher sulfate and glutathione (GSH) levels but lower hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) and malondialdehyde (MDA) contents under drought stress, indicating that ZmSO confers drought tolerance by enhancing GSH-dependent antioxidant system that scavenged ROS and reduced membrane injury. In addition, the transgenic plants exhibited more increased stomatal response than the wild-type (WT) to water deficit. Interestingly, application of exogenous GSH effectively alleviated growth inhibition in both WT and transgenic plants under drought conditions. qPCR analysis revealed that the expression of several sulfur metabolism-related genes was significantly elevated in the ZmSO-overexpressing lines. Taken together, these results imply that ZmSO confers enhanced drought tolerance in transgenic tobacco plants possibly through affecting stomatal regulation, GSH-dependent antioxidant system, and sulfur metabolism-related gene expression. ZmSO could be exploited for developing drought-tolerant maize varieties in molecular breeding.</p

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    <p>Sulfite oxidase (SO) plays a pivotal role in sulfite metabolism. In our previous study, sulfite-oxidizing function of the SO from Zea mays (ZmSO) was characterized. To date, the knowledge of ZmSO’s involvement in abiotic stress response is scarce. In this study, we aimed to investigate the role of ZmSO in drought stress. The transcript levels of ZmSO were relatively high in leaves and immature embryos of maize plants, and were up-regulated markedly by PEG-induced water stress. Overexpression of ZmSO improved drought tolerance in tobacco. ZmSO-overexpressing transgenic plants showed higher sulfate and glutathione (GSH) levels but lower hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) and malondialdehyde (MDA) contents under drought stress, indicating that ZmSO confers drought tolerance by enhancing GSH-dependent antioxidant system that scavenged ROS and reduced membrane injury. In addition, the transgenic plants exhibited more increased stomatal response than the wild-type (WT) to water deficit. Interestingly, application of exogenous GSH effectively alleviated growth inhibition in both WT and transgenic plants under drought conditions. qPCR analysis revealed that the expression of several sulfur metabolism-related genes was significantly elevated in the ZmSO-overexpressing lines. Taken together, these results imply that ZmSO confers enhanced drought tolerance in transgenic tobacco plants possibly through affecting stomatal regulation, GSH-dependent antioxidant system, and sulfur metabolism-related gene expression. ZmSO could be exploited for developing drought-tolerant maize varieties in molecular breeding.</p

    The Maize AAA-Type Protein SKD1 Confers Enhanced Salt and Drought Stress Tolerance in Transgenic Tobacco by Interacting with Lyst-Interacting Protein 5

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    <div><p>ATPase associated with various cellular activities (AAA) proteins are important regulators involved in diverse cellular functions. To date, the molecular mechanisms of AAA proteins involved in response to salt and drought stresses in plants are largely unknown. In this study, a putative <i>SKD1</i> (<u>s</u>uppressor of <u>K</u><sup>+</sup> transport growth <u>d</u>efect 1) ortholog from <i>Zea mays</i> (<i>ZmSKD1</i>), which encodes a putative AAA protein, was isolated. The transcript levels of <i>ZmSKD1</i> were higher in aerial tissues and were markedly up-regulated by salt or drought stress. Over-expression of <i>ZmSKD1</i> in tobacco plants enhanced their tolerances not only to salt but to drought. Moreover, reactive oxygen species accumulations in <i>ZmSKD1</i> transgenic lines were relative less than those in wild-type plants during salt or PEG-induced water stress. The interaction between ZmSKD1 and NtLIP5 (<u>L</u>yst-<u>I</u>nteracting <u>P</u>rotein 5 homolog from <i>Nicotiana tabacum</i>) was confirmed by both yeast two-hybrid and immuno-precipitation assays; moreover, the α-helix-rich domain in the C-terminus of ZmSKD1 was identified to be required for its interaction with NtLIP5 using truncation mutations. Collectively, these data demonstrate that ZmSKD1could be involved in salt and drought stress responses and its over-expression enhances salt or drought stress tolerance possibly through interacting with LIP5 in tobacco. This study may facilitate our understandings of the biological roles of SKD1-mediated ESCRT pathway under stress conditions in higher plants and accelerate genetic improvement of crop plants tolerant to environmental stresses.</p></div

    Phenotypes of wild-type and <i>ZmSKD1</i>-overexpressing tobacco plants in response to drought stress.

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    <p><b>A</b> Drought tolerance of potted plants of wild-type and <i>ZmSKD1</i>-overexpressing tobacco. Four-week-old WT and transgenic OE (OE-7 and OE-10) plants were grown in soil in pots for 14 d without watering, and then rewatering after 3 days. <b>B</b> Fresh weight of drought-stressed wild-type and <i>ZmSKD1</i>-overexpressing plants after 3 days recovery. Values are mean ± SE, n = 6. **t-test, with P<0.01. <b>C</b> Relative remaining chlorophyll (%) of drought-stressed wild-type and <i>ZmSKD1</i>- overexpressing plants after 3 days recovery. Values are mean ± SE, n = 6. **t-test, with P<0.01.</p

    Transcript profiles of <i>ZmSKD1</i> in major organs of maize and its responses to salt and drought stresses.

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    <p><b>A</b> The transcriptional pattern of <i>ZmSKD1</i> in maize root (R), stem (St), leaf (L), tassel (Ta) and immature ear (Ie) samples evaluated by real-time PCR. For each real-time PCR, the transcript levels of maize internal control gene <i>Ubiquitin</i> were also evaluated in various samples. For each assay, the expression level in stems was defined as 1.0, and data represented means ± SE of three technical replicates. *t-test, with P<0.05. <b>B</b> Time-course analysis of <i>ZmSKD1</i> transcript levels under various concentrations of salt treatments by real-time PCR. Two-week-old maize seedlings were exposed to 100, 200, and 300 mM NaCl for indicated time points (0, 6, 12, 24, and 48 h), and leaf samples were used for real-time PCR analysis. <b>C</b> Time-course analysis of <i>ZmSKD1</i> transcript levels under PEG-induced water stress by real-time PCR. Two-week-old maize seedlings were exposed to 0, 10%, 15%, and 20% PEG6000 for indicated time points (0, 6, 12, 24, and 48 h), and leaf samples were used for real-time PCR analysis. In both B and C assays, <i>Ubiquitin</i> was used as an internal control. For each treatment, the expression level at time point 0 was defined as 1.0, and data represented means ± SE of three technical replicates. **t-test, with P<0.01; *t-test, with P<0.05.</p

    Dynamic changes of ROS in wild-type and <i>ZmSKD1</i>-overexpressing tobacco plants in response to salt or PEG-induced water stress.

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    <p><b>A</b> H<sub>2</sub>O<sub>2</sub> production in leaves of wild-type and OE (OE-7) plants treated with distilled water(control), 200 mM NaCl or 15% PEG-6000 solutions, respectively, was visualized by staining with 3, 3′-diaminobenzidine (DAB). Plants were treated for 1, 2, 6, and 12 h, and were subsequently stained with DAB as described in the experimental procedures. <b>B</b> Relative H<sub>2</sub>O<sub>2</sub> levels were quantified in leaves of wild-type and OE (OE-7) plants exposed to 200 mM NaCl or 15% PEG-6000 for 1, 2, 6, and 12 h. Error bars indicate SE (n = 6). **t-test, with P<0.01; *t-test, with P<0.05. <b>C</b> O<sub>2</sub><sup>−</sup> production in leaves of wild-type and OE (OE-7) plants treated with 200 mM NaCl or 15% PEG-6000 solutions, respectively, was visualized by staining with nitroblue tetrazolium (NBT). Plants were treated for 1, 2, 6, and 12 h, and were subsequently stained with NBT as described in the experimental procedures. <b>D</b> Relative O<sub>2</sub><sup>−</sup> levels were quantified in leaves of wild-type and OE (OE-7) plants exposed to 200 mM NaCl or 15% PEG-6000 for 1, 2, 6, and 12 h. Error bars indicate SE (n = 6). **t-test, with P<0.01; *t-test, with P<0.05.</p

    Sequence alignment and phylogenetic analysis of SKD1 proteins from <i>Zea Mays</i> and other species.

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    <p><b>A</b> An alignment is shown for the deduced amino acid sequence of SKD1s from <i>Zea Mays</i> (Zm), <i>Arabidopsis thaliana</i> (At), <i>Lycopersicon esculentum</i> (Le), <i>Oryza sativa</i> (Os), <i>Brachypodium distachyon</i> (Bd), <i>Hordeum vulgare</i> (Hv) and <i>Saccharomyces cerevisiae</i> (Sc). The numbers on the left indicate the amino acid position. Identical residues in all these proteins are shown in a black background. Dashes indicated gaps introduced for optimal alignment. The putative MIT and AAA domains are underlined with a thick red line and a thick green line, respectively. <b>B</b> Phylogenetic tree based on SKD1 protein sequences from yeast, plants, and animals. The bootstrap values shown were calculated based on 500 replications. The tree was constructed using the neighbor-joining method. <i>Z.mays</i>, AY105155; <i>A.thaliana</i>, At2g27600; <i>L.esculentum</i>, AK324437; <i>O.sativa</i>, AF499028; <i>B.distachyon</i>, LOC100837561; <i>H.vulgare</i>, AK359160; <i>D.melanogaster</i>, NP_573258; <i>G.gallus</i>, AJ720732; H.sapiens, AF038960; <i>M.musculus</i>, NP_033216; <i>S.cerevisiae</i>, NP_015499.</p

    Mapping of the ZmSKD1 region involved in SKD1-LIP5 interaction and transcript levels of <i>NtLIP5</i> in responses to salt or PEG-induced water stress in transgenic and wild-type plants.

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    <p><b>A</b> Schematic representation of wild type (WT) and mutant SKD1s in the study. M1 and M4 are C-terminal deletion mutants, and M2 and M3 are N-terminal deletion mutants. MIT marks microtubule-interacting and trafficking; AAA marks ATPase associated with a variety of cellular activities; HRD marks the α-helix-rich domain located at the C-terminus of SKD1. The numbers denote SKD1 amino acid positions. <b>B</b> The interaction between LIP5 or empty vector pGAD-T7 and SKD1 deletions in YTH assays. The ability of SKD1 truncations to interact with LIP5 or AD vector is indicated on the right (+, positive; −, negative). <b>C </b><i>NtLIP5</i> transcript levels under salt or PEG-induced water stress in transgenic and wild-type plants. Four-week-old transgenic and wild-type tobacco plants were exposed to distilled water (control), 15% PEG6000 and 200 mM NaCl for 12 h, respectively, and leaf samples were used for real-time PCR analysis. <i>NtActin</i> was used as an internal control. For each treatment, the expression level under control conditions was defined as 1.0, and data represented means ± SE of three technical replicates. *t-test, with P<0.05.</p

    Phenotypes of wild-type and <i>ZmSKD1</i>-overexpressing tobacco plants in response to salt stress.

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    <p><b>A</b> Transcription levels of <i>ZmSKD1</i> in wild-type (WT) tobacco plants and six homozygous over-expression (OE) lines (named OE-1, OE-2, OE-4, OE-5, OE-7 and OE-10). <i>ZmSKD1</i> transcripts detected by qPCR were present in the OE lines, but not in the wild-type plants. <b>B</b> Growth phenotypes of 2-week-old WT and transgenic OE (OE-7 and OE-10) seedlings vertically growing on 1/2 MS medium supplemented with 0, 100, 200 and 300 mM NaCl for 10 d. <b>C</b> Primary root length of 10 d-salt stressed plants in Fig. B. Values are mean ± SE, n = 10. **t-test, with P<0.01; *t-test, with P<0.05. <b>D</b> Representative phenotype of 6-week-old WT and transgenic OE plants growing in soil pots supplied with 0 (water) or 300 mM NaCl solution every other day for 4 weeks. <b>E</b> Survival rates (%) under salinity stress in Fig. D were determined as the number of visibly green plants after 4 weeks. Values are mean ± SE, n = 10. **t-test, with P<0.01.</p

    Wet-Spun Continuous Graphene Films

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    Macroscopic assembled, self-standing graphene and graphene oxide (GO) films have been demonstrated as promising materials in many emerging fields, such as Li ion battery electrodes, supercapacitors, heat spreaders, gas separation, and water desalination. Such films were mainly available on centimeter-scale via the time- and energy-consuming vacuum-filtration method, which seriously impedes their progress and large-scale applications. Due to the incompatibility between large-scale and ordered assembly structures, it remains a big challenge to access large-area assembled graphene thick films. Here, we report for the first time a fast wet-spinning assembly strategy to produce continuous GO and graphene thick films. A 20 m long, 5 cm wide, well-defined GO film was readily achieved at a speed of 1 m min<sup>–1</sup>. The continuous, strong GO films were easily woven into bamboo-mat-like fabrics and scrolled into highly flexible continuous fibers. The reduced graphene films with high thermal and moderate electrical conductivities were directly used as fast-response deicing electrothermal mats. The fast yet controllable wet-spinning assembly approach paves the way for industrial-scale utilization of graphene
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