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Now showing items 1 - 16 of 56

  • Heterotrimeric G protein signaling in plant immunity

    Zhong, Chen-Li   Zhang, Chi   Liu, Jian-Zhong  

    In animals, heterotrimeric guanine nucleotide-binding proteins (G proteins) transduce signals perceived by numerous G protein-coupled receptors (GPCRs). However, no canonical GPCRs with guanine nucleotide exchange factor (GEF) activity are present in plant genomes. Accumulated evidence indicates that, instead of GPCRs, the receptor-like kinases (RLKs) function upstream of G proteins in plants. Regulator of G protein signaling 1 (RGS1) functions to convert the GTP-bound Ga to the GDP-bound form through its GTPase-accelerating protein (GAP) activity. Because of the intrinsic differences in the biochemical properties between Arabidopsis and animal Ga, the actions of animal and Arabidopsis RGS1 result in contrasting outcomes in G signaling activation/deactivation. Animal RGSs accelerate the deactivation of the activated G signaling, whereas Arabidopsis RGS1 prevents the activation of G signaling in the resting state. Phosphorylation of Arabidopsis RGS1 triggered by ligand-RLK recognition results in the endocytosis or degradation of RGS1, leading to the separation of RGS1 from Ga and thus the derepression of G signaling. Here, we summarize the involvement of the G proteins in plant immunity, with a special focus on the molecular mechanism of G signaling activation/deactivation regulated by RLKs and RGS1. We also provide a brief perspective on the outstanding questions that need to be addressed to fully understand G signaling in plant immunity.
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  • Plant Immunity against Viruses

    Liu, Jian-Zhong   Li, Feng   Liu, Yule  

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  • Signal Transduction Pathways in Plants for Resistance against Pathogens.

    Liu, Jian-Zhong   Lam, Hon-Ming  

    Plants are constantly exposed to a diverse group of pathogens and have evolved sophisticated immune systems to combat pathogen attacks [...].=20
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  • Hetero-trimeric G protein signaling in plant immunity

    Zhong, Chen-Li   Zhang, Chi   Liu, Jian-Zhong  

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  • The MAPK Kinase Kinase GmMEKK1 Regulates Cell Death and Defense Responses

    Xu, Hui-Yang   Zhang, Chi   Li, Zhen-Chao   Wang, Zhi-Rong   Jiang, Xu-Xu   Shi, Ya-Fei   Tian, Sheng-Nan   Braun, Edward   Mei, Yu   Qiu, Wen-Li   Li, Sen   Wang, Bo   Xu, Juan   Navarre, Duroy   Ren, Dongtao   Cheng, Ninghui   Nakata, Paul A.   Graham, Michelle A.   Whitham, Steven A.   Liu, Jian-Zhong  

    MAPK signaling pathways play critical roles in plant immunity. Here, we silenced multiple genes encoding MAPKs using virus-induced gene silencing mediated by Bean pod mottle virus to identify MAPK genes involved in soybean (Glycine max) immunity. Surprisingly, a strong hypersensitive response (HR) cell death was observed when soybean MAPK KINASE KINASE1 (GmMEKK1), a homolog of Arabidopsis (Arabidopsis thaliana) MEKK1, was silenced. The HR was accompanied by the overaccumulation of defense signaling molecules, salicylic acid (SA) and hydrogen peroxide. Genes involved in primary metabolism, translation/transcription, photosynthesis, and growth/development were down-regulated in GmMEKK1-silenced plants, while the expression of defense-related genes was activated. Accordingly, GmMEKK1-silenced plants were more resistant to downy mildew (Peronospora manshurica) and Soybean mosaic virus compared with control plants. Silencing GmMEKK1 reduced the activation of GmMPK6 but enhanced the activation of GmMPK3 in response to flg22 peptide. Unlike Arabidopsis MPK4, GmMPK4 was not activated by either flg22 or SA. Interestingly, transient overexpression of GmMEKK1 in Nicotiana benthamiana also induced HR. Our results indicate that GmMEKK1 plays both positive and negative roles in immunity and appears to differentially activate downstream MPKs by promoting GmMPK6 activation but suppressing GmMPK3 activation in response to flg22. The involvement of GmMPK4 kinase activity in cell death and in flg22- or SA-triggered defense responses in soybean requires further investigation.
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  • Slurryability and combustion characteristics of coal-coking wastewater-slurry

    Wang, Yi   Liu, Jian-Zhong   Chen, Cong   Cheng, Jun  

    The slurryability, rheological properties, stability, and combustion characteristics of coal water slurry (CWS), made from coking wastewater (CW), deionized water, and Shenhua coal were experimentally studied. Results showed that the solid concentration of coal-coking wastewater-slurry (CCWS) could be higher than 60.5 %, which is 0.5-1.5 % lower than that of coal water slurry (CWS). However, the pseudoplastic behaviour of CCWS was greatly evident. The dispersion effects of NNO and NDF were excellent. The stability of CCWS is better than CWS. Moreover, CCWS had lower ignition temperature and burnout temperature, higher combustion characteristic parameters, such as combustion characteristic index S and ignition stability index R-w, and better performance in combustion than CWS. The application of CW for the production of coal water slurry demonstrated the resource utilization of wastewater and improved the combustion characteristic.
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  • Pore Characteristics and Slurryability of Coal Blends

    Zhu, Jie-Feng   Wang, Jie   Liu, Jian-Zhong   Cheng, Jun   Wang, Zhi-Hua   Zhou, Jun-Hu   Cen, Ke-Fa  

    The pore characteristics and slurryability of two coal blends between Shigang anthracite coal and Huangling bituminous coal (SG/HL), and Guizhou anthracite coal and Xiaotun lean coal (GZ/XT), respectively, were investigated. The fractal dimensions of coal were calculated in the two regions of P/P-0 < 0.45 and P/P-0 > 0.45 and defined as D, and D-2, respectively. Upon an increase in the blending ratio of parent coal with smaller BET surface area (SBET) and total pore volume (TPV), the S-BET and TPV of coal blends monotonously decreased. D-1 was mainly related to the Smeso/macro(10-220 nm)/S-total and mineral phase within coal while D-2 was closely affected by the Vmeso(2-10 nm)/V-total. D-1 of SG/HL coal blends had no apparent linear correlation with the pore structure parameters whereas I), of GZ/XT coal blends changed linearly with the pore structure parameters. Both D-2 of SG/HL coal blends and that of GZ/XT coal blends changed linearly with the pore structure parameters. The slurry quality of coal water slurry (CWS) prepared from coal blends is comprehensively affected by the physicochemical properties and blending ratio of parent coals. Therefore, the maximum solid loading (MSL) and water separation ratio (WSR) of CWS prepared from coal blends do not always change linearly with the blending ratio of parent coal.
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  • Metabolic engineering of Escherichia coli to produce zeaxanthin.

    Li, Xi-Ran   Tian, Gui-Qiao   Shen, Hong-Jie   Liu, Jian-Zhong  

    Zeaxanthin is a high-value carotenoid that is used in nutraceuticals, cosmetics, food, and animal feed industries. Zeaxanthin is chemically synthesized or purified from microorganisms as a natural product; however, increasing demand requires development of alternative sources such as heterologous biosynthesis by recombinant bacteria. For this purpose, we molecularly engineered Escherichia coli to optimize the synthesis of zeaxanthin from lycopene using fusion protein-mediated substrate channeling as well as by the introduction of tunable intergenic regions. The tunable intergenic regions approach was more efficient compared with protein fusion for coordinating expression of lycopene beta-cyclase gene crtY and beta-carotene 3-hydroxylase gene crtZ. The influence of the substrate channeling effect suggests that the reaction catalyzed by CrtZ is the rate-limiting step in zeaxanthin biosynthesis. Then Pantoea ananatis, Pantoea agglomerans and Haematococcus pluvialis crtZ were compared. Because P. ananatis crtZ is superior to that of P. agglomerans or H. pluvialis for zeaxanthin production, we used it to generate a recombinant strain of E. coli BETA-1 containing pZSPBA-2(P37-crtZPAN) that produced higher amounts of zeaxanthin (11.95=C2=B10.21mg/g dry cell weight) than other engineered E. coli strains described in the literature. =20
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  • Effect of magnesium on the burning characteristics of boron particles

    Liu, Jian-zhong   Xi, Jian-fei   Yang, Wei-juan   Hu, You-rui   Zhang, Yan-wei   Wang, Yang   Zhou, Jun-hu  

    Boron is an attractive fuel for propellants and explosives because of its high energy density. However, boron particles are difficult to combust because of inhibiting oxide layers that cover the particles. The use of magnesium as additives has been shown to promote boron oxidation. In this study, laser ignition facility and thermobalance were used to investigate the effect of magnesium on the burning characteristics of boron particles. The influences of magnesium addition on sample combustion flame, boron ignition delay time, boron combustion efficiency and initial temperature of boron oxidation. Results show that all Mg/B samples exhibit the same type of flame structure, i.e., a bright plume surrounded by green radiation which is interpreted as BO2 emission. The combustion flame intensity of a sample increases with the increasing magnesium content of boron particles. An increase in magnesium content results in a decrease and a subsequent increase in boron ignition delay time. (Mg/B)(0.2) has a minimum ignition delay time of similar to 48 ms. Boron combustion efficiency increases with increasing magnesium addition. (Mg/B)(0.5) shows a maximum boron combustion efficiency of similar to 64.2%. Magnesium addition decreases the initial temperature of boron oxidation. (C) 2013 IAA. Published by Elsevier Ltd. All rights reserved.
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  • Slurry characteristics and mechanism analysis of petroleum coke-coal water slurry

    Wang, Shuang-Ni   Liu, Jian-Zhong   Wang, Yi   Li, Ning   Cen, Ke-Fa  

    Petroleum coke-coal slurry (PCCS) was prepared by blending sub-bituminous coal with petroleum coke in different proportions. The rheology and stability of PCCS were studied, and the mechanism of dispersion and stability was analyzed. Results show that with the increase of the mass ratio of petroleum coke to Shenhua coal (alpha) in PCCS, the apparent viscosity of the slurry gradually increases, and the stability of the slurry decreases. Moreover, the contact angle also increases, indicating that the surface hydrophobicity was increased. When the alpha is 3:7, the fixed viscosity concentration of PCCS is above 60%, the fixed viscosity flow characteristic index is below 0.9, and the fixed segregation water rate is below 5%. Blending petroleum coke with Shenhua coal takes advantage of the complementary properties of the two materials and obtains PCCS with high concentration and improved stability.
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  • Slurry characteristics and mechanism analysis of petroleum coke-coal water slurry

    Wang, Shuang-Ni   Liu, Jian-Zhong   Wang, Yi   Li, Ning   Cen, Ke-Fa  

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  • Positive and Negative Roles for Soybean MPK6 in Regulating Defense Responses

    Liu, Jian-Zhong   Braun, Edward   Qiu, Wen-li   Shi, Ya-Fei   Marcelino-Guimar?es, Francismar C.   Navarre, Duroy   Hill, John H.   Whitham, Steven A.  

    It has been well established that MPK6 is a positive regulator of defense responses in model plants such as Arabidopsis and tobacco. However, the functional importance of soybean MPK6 in disease resistance has not been investigated. Here, we showed that silencing of GmMPK6 in soybean using virus-induced gene silencing mediated by Bean pod mottle virus (BPMV) caused stunted growth and spontaneous cell death on the leaves, a typical phenotype of activated defense responses. Consistent with this phenotype, expression of pathogenesis-related (PR) genes and the conjugated form of salicylic acid were significantly increased in GmMPK6-silenced plants. As expected, GmMPK6-silenced plants were more resistant to downy mildew and Soybean mosaic virus compared with vector control plants, indicating a negative role of GmMPK6 in disease resistance. Interestingly, overexpression of GmMPK6, either transiently in Nicotiana benthamiana or stably in Arabidopsis, resulted in hypersensitive response (HR)-like cell death. The HR-like cell death was accompanied by increased PR gene expression, suggesting that GmMPK6, like its counterpart in other plant species, also plays a positive role in cell death induction and defense response. Using bimolecular fluorescence complementation analysis, we determined that GmMKK4 might function upstream of GmMPK6 and GmMKK4 could interact with GmMPK6 independent of its phosphorylation status. Taken together, our results indicate that GmMPK6 functions as both repressor and activator in defense responses of soybean.
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  • Positive and negative roles for soybean MPK6 in regulating defense responses.

    Liu, Jian-Zhong   Braun, Edward   Qiu, Wen-Li   Shi, Ya-Fei   Marcelino-Guimaraes, Francismar C   Navarre, Duroy   Hill, John H   Whitham, Steven A  

    It has been well established that MPK6 is a positive regulator of defense responses in model plants such as Arabidopsis and tobacco. However, the functional importance of soybean MPK6 in disease resistance has not been investigated. Here, we showed that silencing of GmMPK6 in soybean using virus-induced gene silencing mediated by Bean pod mottle virus (BPMV) caused stunted growth and spontaneous cell death on the leaves, a typical phenotype of activated defense responses. Consistent with this phenotype, expression of pathogenesis-related (PR) genes and the conjugated form of salicylic acid were significantly increased in GmMPK6-silenced plants. As expected, GmMPK6-silenced plants were more resistant to downy mildew and Soybean mosaic virus compared with vector control plants, indicating a negative role of GmMPK6 in disease resistance. Interestingly, overexpression of GmMPK6, either transiently in Nicotiana benthamiana or stably in Arabidopsis, resulted in hypersensitive response (HR)-like cell death. The HR-like cell death was accompanied by increased PR gene expression, suggesting that GmMPK6, like its counterpart in other plant species, also plays a positive role in cell death induction and defense response. Using bimolecular fluorescence complementation analysis, we determined that GmMKK4 might function upstream of GmMPK6 and GmMKK4 could interact with GmMPK6 independent of its phosphorylation status. Taken together, our results indicate that GmMPK6 functions as both repressor and activator in defense responses of soybean. =20
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  • Pore structure and fractal analysis of Ximeng lignite under microwave irradiation

    Liu, Jian-Zhong   Zhu, Jie-Feng   Cheng, Jun   Zhou, Jun-Hu   Cen, Ke-Fa  

    The pore structure and fractal analysis of Ximeng lignite (XL) under microwave irradiation were investigated. Effects of drying temperature, microwave irradiation time, and microwave power level were studied. The pore structures of XL were obtained by N-2 adsorption/desorption at 77 K. Two fractal dimensions, D-1 and D-2, at relative pressures of 0-0.5 and 0.5-1, respectively, were calculated with the fractal Frenkel-Halsey-Hill model. The specific surface area of the microwave-treated XL differently decreased, whereas its average pore diameter and total pore volume differently increased. However, the evolution mechanisms of pore structures during microwave drying were similar. These mechanisms included the collapse of pore structures caused by shrinkage forces that resulted from the removal of moisture, open and cross-linking of blind and closed pores, and thermal decomposition of organic macromolecular structures under a high temperature. The changes in D-1 were similar to those in average pore diameter development, whereas the changes in D-2 were consistent with those in specific surface area development. The reliability of the relationship between D-2 and mesopores was examined with some scanning electron microscope images and D-2 can reflect the volumetric roughness of mesopores. (C) 2015 Elsevier Ltd. All rights reserved.
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  • Gaining insight into soybean defense responses using functional genomics approaches.

    Liu, Jian-Zhong   Graham, Michelle A   Pedley, Kerry F   Whitham, Steven A  

    Soybean pathogens significantly impact yield, resulting in over $4 billion dollars in lost revenue annually in the United States. Despite the deployment of improved soybean cultivars, pathogens continue to evolve to evade plant defense responses. Thus, there is an urgent need to identify and characterize gene networks controlling defense responses to harmful pathogens. In this review, we focus on major advances that have been made in identifying the genes and gene networks regulating defense responses with an emphasis on soybean-pathogen interactions that have been amenable to gene function analyses using gene silencing technologies. Further we describe new research striving to identify genes involved in durable broad-spectrum resistance. Finally, we consider future prospects for functional genomic studies in soybean and demonstrate that understanding soybean disease and stress tolerance will be expedited at an unprecedented pace. =C2=A9 The Author 2015. Published by Oxford University Press. All rights reserved. For permissions, please email: journals.permissions@oup.com.
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  • Chromosomal evolution of Escherichia coli for the efficient production of lycopene

    Chen, Yun-Yan   Shen, Hong-Jie   Cui, Yan-Yan   Chen, Shang-Guang   Weng, Zhi-Ming   Zhao, Ming   Liu, Jian-Zhong  

    Background: Plasmid-based overexpression of genes has been the principal strategy for metabolic engineering. However, for biotechnological applications, plasmid-based expression systems are not suitable because of genetic instability, and the requirement for constant selective pressure to ensure plasmid maintenance. Results: To overcome these drawbacks, we constructed an Escherichia coli lycopene production strain that does not carry a plasmid or an antibiotic marker. This was achieved using triclosan-induced chromosomal evolution, a high gene copy expression system. The engineered strain demonstrated high genetic stability in the absence of the selective agent during fermentation. The replacement of native appY promoter with a T5 promoter, and the deletion of the iclR gene in E. coli CBW 12241 further improved lycopene production. The resulting strain, E. coli CBW 12241(Delta iclR, P-T5-appY), produced lycopene at 33.43 mg per gram of dry cell weight. Conclusions: A lycopene hyper-producer E. coli strain that does not carry a plasmid or antibiotic marker was constructed using triclosan-induced chromosomal evolution. The methods detailed in this study can be used to engineer E. coli to produce other metabolites.
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