甜瓜幼苗叶片内源一氧化氮和蔗糖代谢对低温胁迫的响应

以低温敏感型甜瓜品种‘XL-1’和耐低温型品种‘红优’为试材,采用6℃低温处理0、1、3、6、12、24h及3d、5d和7d,研究低温胁迫下甜瓜幼苗叶片中NO合成和蔗糖代谢的变化特征。结果表明:(1)低温胁迫能提高甜瓜幼苗叶片中硝酸还原酶(NR)活性,诱导促进NO生成,其中耐低温型甜瓜‘红优’中NO对低温的响应时间更早,变化幅度更大。(2)与对照相比,低温胁迫处理提高了2种甜瓜幼苗叶片中蔗糖、果糖和葡萄糖含量,增加了蔗糖磷酸合成酶(SPS)、蔗糖合成酶(SS)、酸性转化酶(AI)和中性转化酶(NI)活性,降低了淀粉含量。(3)低温胁迫处理使2种甜瓜叶片中渗透调节物质可溶性糖、可溶性蛋白、脯氨酸的含量上升。研究发现,低温胁迫通过增加甜瓜体内NO合成酶的活性刺激体内NO合成,通过促进蔗糖代谢相关酶的活性,提高蔗糖、果糖和葡萄糖的含量,从而响应低温胁迫,且低温胁迫诱导的糖分物质积累时间晚于NO的产生时间。     

CgMFS1, a Major Facilitator Superfamily Transporter,Is Required for Sugar Transport,Oxidative Stress Resistance,and Pathogenicity of Colletotrichum gloeosporioides from Hevea brasiliensis

Colletotrichum gloeosporioides is the main causal agent of anthracnose in various plant species. Determining the molecular mechanisms underlying the pathogenicity and fungicide resistance of C. gloeosporioides could help build new strategies for disease control. The major facilitator superfamily (MFS) has multiple roles in the transport of a diverse range of substrates. In the present study, an MFS protein CgMFS1 was characterized in C. gloeosporioides. This protein contains seven transmembrane domains, and its predicted 3D structure is highly similar to the reported hexose transporters. To investigate the biological functions of CgMFS1, the gene knock-out mutant ΔCgMFS1 was constructed. A colony growth assay showed that the mutant was remarkably decreased in vegetative growth in minimal medium supplemented with monosaccharides and oligosaccharides as the sole carbon sources, whereas it showed a similar growth rate and colony morphology as wild types when using soluble starch as the carbon source. A stress assay revealed that CgMFS1 is involved in oxidative stress but not in the fungicide resistance of C. gloeosporioides. Furthermore, its pathogenicity was significantly impaired in the mutant, although its appressorium formation was not affected. Our results demonstrate that CgMFS1 is required for sugar transport, resistance to oxidative stress, and the pathogenicity of Colletotrichum gloeosporioides from Hevea brasiliensis.     

A micro potentiometric immunosensor for hemoglobin-A1c level detection based on mixed SAMs wrapped nano-spheres array

A micro potentiometric immunosensor based on mixed SAMs wrapped nano-spheres array for the detection of hemoglobin-A1c level is presented in this paper. Nano-spheres array is prepared by wrapping nano-gold particle with mixed SAMs on the surface of micro immunosensor. Mixed SAMs make the nano-gold particles distribute uniformly without aggregation and render the signal less susceptible to noise. Based on this nano-spheres array, antibody is covalently immobilized on the immunosensor surface. The micro immunosensor, consisting of ISFET integrated chip and MEMS electrodes array is applied to measure hemoglobin-A1c level by detecting the concentration of hemoglobin-A1c and hemoglobin simultaneously. The responses of the immunosensor are linear over the concentration range of 166.7-570 ng/ml hemoglobin and 50-170.5 ng/ml HbA1c. Whole blood sample obtained from hospital was also examined using this immunosensor. The low relative deviation shows that this micro immunosensor may provide an alternative tool for the determination of HbA1c level.     

Manipulating Molecular Structure and Morphology to Invoke High‐Performance Sodium Storage of Copper Phosphide

Copper is used as current collector in rechargeable ion batteries due to its outstanding electronic conductivity and low cost. The intrinsic inactivity of copper, however, makes it a poor candidate for an electrode material without further structural modification. To fully utilize its high electronic conductivity, herein, the incorporation of heterogeneous phosphorus combined with building a unique 3D hollow structure is proposed. The as‐prepared copper phosphide hollow nanocubes deliver a stable capacity of 325 mAh·g^?1 at 50 mA·g^?1 and fast charging and discharging via pseudocapacitance behavior. The outstanding electrochemical performance is attributed to the synergetic effects of high electronic conductivity of copper and the high sodium storage capability of phosphorus. In addition, this facile synthesis method is also easily scaled up for practical applications. Thus, copper phosphide is a promising anode material for sodium ion batteries.     

Arabidopsis VILLIN5, an Actin Filament Bundling and Severing Protein, Is Necessary for Normal Pollen Tube Growth

A dynamic actin cytoskeleton is essential for pollen germination and tube growth. However, the molecular mechanisms underlying the organization and turnover of the actin cytoskeleton in pollen remain poorly understood. Villin plays a key role in the formation of higher-order structures from actin filaments and in the regulation of actin dynamics in eukaryotic cells. It belongs to the villin/gelsolin/fragmin superfamily of actin binding proteins and is composed of six gelsolin-homology domains at its core and a villin headpiece domain at its C terminus. Recently, several villin family members from plants have been shown to sever, cap, and bundle actin filaments in vitro. Here, we characterized a villin isovariant, Arabidopsis thaliana VILLIN5 (VLN5), that is highly and preferentially expressed in pollen. VLN5 loss-of-function retarded pollen tube growth and sensitized actin filaments in pollen grains and tubes to latrunculin B. In vitro biochemical analyses revealed that VLN5 is a typical member of the villin family and retains a full suite of activities, including barbed-end capping, filament bundling, and calcium-dependent severing. The severing activity was confirmed with time-lapse evanescent wave microscopy of individual actin filaments in vitro. We propose that VLN5 is a major regulator of actin filament stability and turnover that functions in concert with oscillatory calcium gradients in pollen and therefore plays an integral role in pollen germination and tube growth.