Browsing by Author "Shen, Zhengxing"
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- No-till Organic Culture of Garlic Utilizing Different Cover Crop Residues and Straw Mulch for Over-wintering Protection, Under Two Seasonal Levels of Organic NitrogenBratsch, Tony; Morse, Ronald; Shen, Zhengxing; Benson, Brinkley (Virginia Cooperative Extension, 2009-08-17)In 2003 and 2004, we evaluated the potential for no-till planting into beds with a frost killed, standing cover crop in place. Three cover crops, Sorghum Sudangrass, a thick grassy cover crop, Lablab (soybean like legume), and Sunhemp, a tropical legume, were evaluated. This publication reviews the methods and results for this evaluation.
- Overexpression of AtLOV1 in Switchgrass Alters Plant Architecture, Lignin Content, and Flowering TimeXu, Bin; Sathitsuksanoh, Noppadon; Tang, Yuhong; Udvardi, Michael K.; Zhang, Ji-Yi; Shen, Zhengxing; Balota, Maria; Harich, Kim; Zhang, Y. H. Percival; Zhao, Bingyu Y. (2012-12-26)Background: Switchgrass (Panicum virgatum L.) is a prime candidate crop for biofuel feedstock production in the United States. As it is a self-incompatible polyploid perennial species, breeding elite and stable switchgrass cultivars with traditional breeding methods is very challenging. Translational genomics may contribute significantly to the genetic improvement of switchgrass, especially for the incorporation of elite traits that are absent in natural switchgrass populations. Methodology/Principal Findings: In this study, we constitutively expressed an Arabidopsis NAC transcriptional factor gene, LONG VEGETATIVE PHASE ONE (AtLOV1), in switchgrass. Overexpression of AtLOV1 in switchgrass caused the plants to have a smaller leaf angle by changing the morphology and organization of epidermal cells in the leaf collar region. Also, overexpression of AtLOV1 altered the lignin content and the monolignol composition of cell walls, and caused delayed flowering time. Global gene-expression analysis of the transgenic plants revealed an array of responding genes with predicted functions in plant development, cell wall biosynthesis, and flowering. Conclusions/Significance: To our knowledge, this is the first report of a single ectopically expressed transcription factor altering the leaf angle, cell wall composition, and flowering time of switchgrass, therefore demonstrating the potential advantage of translational genomics for the genetic improvement of this crop.
- Skeletal muscle O-GlcNAc transferase is important for muscle energy homeostasis and whole-body insulin sensitivityShi, Hao; Munk, Alexander; Nielsen, Thomas S.; Daughtry, Morgan R.; Larsson, Louise; Li, Shize; Hoyer, Kasper F.; Geisler, Hannah W.; Sulek, Karolina; Kjobsted, Rasmus; Fisher, Taylor; Andersen, Marianne M.; Shen, Zhengxing; Hansen, Ulrik K.; England, Eric M.; Cheng, Zhiyong; Hojlund, Kurt; Wojtaszewski, Jorgen FP P.; Yang, Xiaoyong; Hulver, Matthew W.; Helm, Richard F.; Treebak, Jonas T.; Gerrard, David E. (Elsevier, 2018-05-01)Objective: Given that cellular O-GlcNAcylation levels are thought to be real-time measures of cellular nutrient status and dysregulated O-GlcNAc signaling is associated with insulin resistance, we evaluated the role of O-GlcNAc transferase (OGT), the enzyme that mediates O-GlcNAcylation, in skeletal muscle. Methods: We assessed O-GlcNAcylation levels in skeletal muscle from obese, type 2 diabetic people, and we characterized muscle-specific OGT knockout (mKO) mice in metabolic cages and measured energy expenditure and substrate utilization pattern using indirect calorimetry. Whole body insulin sensitivity was assessed using the hyperinsulinemic euglycemic clamp technique and tissue-specific glucose uptake was subsequently evaluated. Tissues were used for histology, qPCR, Western blot, co-immunoprecipitation, and chromatin immunoprecipitation analyses. Results: We found elevated levels of O-GlcNAc-modified proteins in obese, type 2 diabetic people compared with well-matched obese and lean controls. Muscle-specific OGT knockout mice were lean, and whole body energy expenditure and insulin sensitivity were increased in these mice, consistent with enhanced glucose uptake and elevated glycolytic enzyme activities in skeletal muscle. Moreover, enhanced glucose uptake was also observed in white adipose tissue that was browner than that of WT mice. Interestingly, mKO mice had elevated mRNA levels of Il15 in skeletal muscle and increased circulating IL-15 levels. We found that OGT in muscle mediates transcriptional repression of Il15 by O-GlcNAcylating Enhancer of Zeste Homolog 2 (EZH2). Conclusions: Elevated muscle O-GlcNAc levels paralleled insulin resistance and type 2 diabetes in humans. Moreover, OGT-mediated signaling is necessary for proper skeletal muscle metabolism and whole-body energy homeostasis, and our data highlight O-GlcNAcylation as a potential target for ameliorating metabolic disorders.
- Studies on the Plasticity of Dormancy and on Aging in Switchgrass SeedsShen, Zhengxing (Virginia Tech, 1997-07-02)The dormancy of switchgrass (Panicum virgatum L.) seeds may be broken by a variety of treatments, including after-ripening and stratification. This study was conducted to investigate and characterize more systematically factors affecting both after-ripening and stratification effectiveness, and the aging that can occur concomitantly with after-ripening. More than one year of after-ripening at ambient temperature and humidity was necessary for germination of newly harvested seeds to increase from as low as 5% to around 80%. After-ripening was not accelerated at temperatures above ambient for seeds stored in paper bags, which permitted the loss of seed moisture at the increased temperatures. Both after-ripening and aging accelerated with increases in temperature (5 to 60°C) and seed moisture content (50 to 130 g kg⁻¹), except that there was evidence of a moisture optimum for after-ripening that shifted downward as temperature increased. For many seedlots, storage at 60°C and 50 g kg⁻¹ seed moisture content for about 1 mo broke most of the dormancy and resulted in acceptably low numbers of abnormal (aged) seedlings. Decreases in germinability caused by post-stratification drying of switchgrass seeds (described herein as "reversion", in which the reverted seeds could be made germinable again by further stratification) increased as the desiccation increased. Revertibility decreased as stratification or after-ripening time increased. Stratification and after-ripening worked additively to release switchgrass seeds from dormancy. Reversion (germination with stratification minus germination after stratification followed by drying) may reveal seedlot differences and changes over time and moisture content that can not be seen otherwise. Imbibed, dormant seeds placed at 21 or 30°C were induced into deeper dormancy, as indicated by length of stratification needed to break the dormancy. Dormancy deepened more as storage temperature and time increased for imbibed seeds. There are transitional temperature and seed moisture ranges where opposing processes (aging vs. after-ripening, stratification vs. dormancy deepening) appeared to overlap or surpass one another. Switchgrass seeds, either on a single seed level, or on the population level, responded continuously to changing temperature and moisture conditions. Less aging was observed for switchgrass seeds stored in N₂. After-ripening of switchgrass seemed not to be influenced by N₂ or air. In sum, switchgrass is revealed to be remarkably plastic in its ability to move toward both greater germinability and greater dormancy.