The effects of Bacillus thuringiensis Cry6A on the survival, growth, reproduction, locomotion, and behavioral response of Caenorhabditis elegans

Several families of crystal proteins from Bacillus thuringiensis exhibit nematicidal activity. Cry5B protein, a pore-forming toxin, has been intensively studied yielding many insights into the mode of action of crystal protein at molecular level and pathogenesis of pore-forming toxins. However, little attention was paid to Cry6A, another representative nematicidal crystal protein. Cry6A shares very low homology with Cry5B at amino acid sequence and probably acts in a distinct pathway from Cry5B and even the other main commercial crystal proteins. In the current study, we comprehensively investigated the nematicidal properties of Cry6Aa2 against the free-living soil nematode Caenorhabditis elegans and examined the physical response of C. elegans to Cry6Aa2 attack. Our results indicate that Cry6Aa2 exhibits high lethal activity to C. elegans and could cause detrimental effects on C. elegans, including obviously suppressed growth, decreased brood size, and even abnormal motility. Meanwhile, our study additionally shows that C. elegans could defend against the Cry6Aa2 toxin harmful threat through behavioral defense responses, such as reduced oral uptake and physical avoidance. In general, this study suggests that Cry6Aa2 possesses diverse nematicidal properties, which strongly indicates that Cry6Aa2 is a promising potential candidate of nematicidal agent. Moreover, this study highlights the importance of behavioral responses in defense of C. elegans for survival and demonstrates the key role of crystal protein in the interaction of B. thuringiensis–C. elegans. These findings could shed light on understanding the interaction of C. elegans with B. thuringiensis and provide a perfect model to study the role of pathogenic factor in the interaction of pathogen–host.     

雷氏大疣蛛毒素—Ⅱ的纯化与初步毒性研究

雷氏大疣蛛是我国最近鉴定的蜘蛛新种。雷氏大疣蛛毒素－Ⅱ就是以其粗毒为材料,利用阴、阳离子交换层析和反相HPLC分离得到并命名的一种新型神经毒素肽,根据质谱分析得知它的相对分子质量为3021．56;通过初步毒性研究,证明它是一个神经毒素。     

Genome-wide regulation of 5hmC, 5mC, and gene expression by Tet1 hydroxylase in mouse embryonic stem cells

DNA methylation at the 5 position of cytosine (5mC) in the mammalian genome is a key epigenetic event critical for various cellular processes. The ten-eleven translocation (Tet) family of 5mC-hydroxylases, which convert 5mC to 5-hydroxymethylcytosine (5hmC), offers a way for dynamic regulation of DNA methylation. Here we report that Tet1 binds to unmodified C or 5mC- or 5hmC-modified CpG-rich DNA through its CXXC domain. Genome-wide mapping of Tet1 and 5hmC reveals mechanisms by which Tet1 controls 5hmC and 5mC levels in mouse embryonic stem cells (mESCs). We also uncover a comprehensive gene network influenced by Tet1. Collectively, our data suggest that Tet1 controls DNA methylation both by binding to CpG-rich regions to prevent unwanted DNA methyltransferase activity, and by converting 5mC to 5hmC through hydroxylase activity. This Tet1-mediated antagonism of CpG methylation imparts differential maintenance of DNA methylation status at Tet1 targets, ultimately contributing to mESC differentiation and the onset of embryonic development.     

The role of cytokines in the regulation of Leydig cell P450c17 gene expression

Cytokines produced by immune-activated testicular interstitial macrophages (TIMs) may play a fundamental role in the local control mechanisms of testosterone biosynthesis in Leydig cells. We investigated whether in vivo immune-activation of TIMs can modulate Leydig cell steroidogenesis. To immune activate TIMs in vivo, mice were injected intraperitoneally (i.p.) with lipopolysaccharide (LPS, 6 mg/kg). TIMs and Leydig cells were purified for RNA analysis. LPS treatment resulted in a 47-fold increase in interleukin-1β (IL-1β) mRNA in TIMs. P450c17 mRNA levels in the Leydig cells from the same animals, decreased to less than 10% compared to control. The effect of LPS on IL-1β and P450c17 mRNA levels was reversible on both TIMs and Leydig cells, respectively. To determine if the effect of LPS on P450c17 was mediated by a possible decrease in pituitary LH secretion, mice were co-injected with LPS and hCG. Treatment with hCG did not change the effect observed with LPS alone, in TIMs or in Leydig cells. In vitro, LPS treatment of TIMs resulted in marked induction of IL-1β mRNA expression. In parallel, in vitro treatment of Leydig cells with recombinant IL-1 resulted in a dose-dependent inhibition of P450c17 mRNA expression and testosterone production. These data demonstrate that LPS treatment, in vivo and in vitro, induced IL-1 gene expression in TIMs, and that IL-1 inhibits P450c17 mRNA in vitro. Therefore, we suggest that immune-activation of TIMs might have caused the observed inhibition of P450c17 gene expression in Leydig cells in vivo.     

2-吗啉乙磺酸(MES)对拟南芥幼苗生长的影响

本实验研究0.05% MES对野生型拟南芥生长的影响。结果表明,含有MES的培养基pH变化较小,其培养10 d的拟南芥幼苗干重、鲜重、叶绿素含量和含水量均高于对照组,而叶片PAL和POD活性却低于对照组,说明MES通过影响培养基的pH变化促进拟南芥生长。     

厦门市交通主干道绿化带结构及其减噪效果研究

通过对厦门市主干道绿化带种类结构调查以及噪声测定等,分析了厦门市主干道绿化带结构及其减噪效果。结果表明,厦门市主干道绿化带可分为4种结构:单一乔木型、乔木+疏灌木/绿篱型、乔木+密灌木型以及乔木+小乔木+灌木/绿篱型,带宽多在4~10 m。厦门市主干道绿化带总体减噪能力为0.93~12.96 dB,绿化带对交通噪声超标治理率达70%。绿化带减噪能力y(dB)与带宽x(m)呈显著的线性关系:y=1.2251x+0.2416(R²=0.8603);绿化带的附加衰减与总衰减亦呈显著正相关:y=0.4535x+0.2698 (R²=0.9242),噪声的附加衰减主要受绿化带结构的影响,上述四种结构对噪声附加衰减平均值分别达0.93、2.25、4.43和6.72 dB。绿化带的宽度和结构均是影响其减噪效果的关键因素。     

不同覆盖方式对底泥内源营养盐释放的控制效果

通过底泥内源营养盐释放控制室内模拟试验,考察了塑料包被、斜发沸石、方解石、石英砂和硝酸钙5种覆盖材料对底泥氮磷释放效率的影响,系统分析了各自优劣程度,为实际环境中不同污染背景水体选择适宜的控制技术提供科学依据.结果表明: 不同覆盖材料对底泥总磷释放的控制效果依次为:塑料包被>硝酸钙>斜发沸石>方解石>石英砂;不同覆盖材料对底泥总氮释放的控制效果依次为:斜发沸石>塑料包被>方解石>石英砂>硝酸钙;不同覆盖材料对底泥硝态氮释放的控制效果依次为:塑料包被>斜发沸石>方解石>石英砂>硝酸钙;不同覆盖材料对底泥铵态氮释放的控制效果依次为:硝酸钙>石英砂>斜发沸石>方解石>塑料包被;温度和底泥内源营养盐释放有对应关系,水样中总磷、总氮和硝态氮浓度会随着温度上升而增加,而铵态氮浓度呈下降趋势.