外源基因表达造成的群体感应细菌生存压力的建模分析

外源基因的表达及其对细菌种群的影响对于群体感应系统和合成生物学产业的研究具有重要意义。然而,人们对于表达外源蛋白的细菌本身的行为模式仍然知之甚少。为了研究菌落生长和外源基因表达的过程究竟受到哪些因素的影响,文中测量了受Lux类受体调控的外源基因在N-酰基高丝氨酸内酯 (N-acyl homoserine lactone,N-AHL) 信号分子诱导下的表达,并模拟了其对细菌种群动态的影响。文中建立了一个假设性的数学模型,对信号分子诱导表达下细菌种群生长受影响的现象进行了分析。先前的研究通常将细菌种群生长受群体感应系统影响的现象归咎于合成群体感应信号分子的消耗与N-AHL信号分子的毒性,文中提供了对于这种生存压力的另一种可能的解释。     

Quantification of bacterial adhesion forces using atomic force microscopy (AFM)

This study demonstrated that atomic force microscopy (AFM) can be used to obtain high-resolution topographical images of bacteria, and to quantify the tip-cell interaction force and the surface elasticity. Results show that the adhesion force between the Si3N4 tip and the bacteria surface was in the range from -3.9 to -4.3 nN. On the other hand, the adhesion forces at the periphery of the cell-substratum contact surface ranged from -5.1 to -5.9 nN and those at the cell-cell interface ranged from -6.5 to -6.8 nN. The two latter forces were considerably greater than the former one, most likely due to the accumulation of extracellular polymer substance (EPS). Results also show that the elasticity varied on the cell surface.     

Separation of allelopathy from resource competition using rice/barnyardgrass mixed-cultures

Plant-plant interference is the combined effect of allelopathy, resource competition, and many other factors. Separating allelopathy from resource competition is almost impossible in natural systems but it is important to evaluate the relative contribution of each of the two mechanisms on plant interference. Research on allelopathy in natural and cultivated plant communities has been hindered in the absence of a reliable method that can separate allelopathic effect from resource competition. In this paper, the interactions between allelopathic rice accession PI312777, non-allelopathic rice accession Lemont and barnyardgrass were explored respectively by using a target (rice)-neighbor (barnyardgrass) mixed-culture in hydroponic system. The relative competitive intensity (RCI), the relative neighbor effect (RNE) and the competitive ratio (CR) were used to quantify the intensity of competition between each of the two different potentially allelopathic rice accessions and barnyardgrass. Use of hydroponic culture system enabled us to exclude any uncontrolled factors that might operate in the soil and we were able to separate allelopathy from resource competition between each rice accession and barnyardgrass. The RCI and RNE values showed that the plant-plant interaction was positive (facilitation) for PI312777 but that was negative (competition) for Lemont and barnyardgrass in rice/barnyardgrass mixed-cultures. The CR values showed that one PI312777 plant was more competitive than 2 barnyardgrass plants. The allelopathic effects of PI312777 were much more intense than the resource competition in rice/barnyardgrass mixed cultures. The reverse was true for Lemont. These results demonstrate that the allelopathic effect of PI312777 was predominant in rice/barnyardgrass mixed-cultures. The most significant result of our study is the discovery of an experimental design, target-neighbor mixed-culture in combination with competition indices, can successfully separate allelopathic effects from competition.     

Polymorphisms associated with egg number at 300 days of age in chickens

We looked for variations that could be associated with chicken egg number at 300 days of age (EN300) in seven genes of the hypothalamic-pituitary-gonadal axis, including gonadotrophin-releasing hormone-I (GnRH-I), GnRH receptor (GnRHR), neuropeptide Y (NPY), dopamine D2 receptor (DRD2), vasoactive intestinal polypeptide (VIP), VIP receptor-1 (VIPR-1), prolactin (PRL), and the QTL region between 87 and 105 cM of the Z chromosome. Ten mutations in the seven genes were chosen to do marker-trait association analyses in a population comprising 1310 chickens, which were obtained from a company located in Guangdong Province of China. The C1704887T of VIPR-1 was found to have a highly significant association with EN300. The T5841629C of DRD2 and the C1715301T of VIPR-1 were significantly associated with EN300. A highly significant association was also found between the C1704887T-C1715301T haplotypes of VIPR-1 and EN300. H1H3 had the highest EN300. Four PCR-RFLP variations in the candidate QTL region were selected to investigate their genetic effects on EN300. The haplotypes of T32742468C-G32742603A in this region showed a highly significant association with EN300. Bioinformatics analyses showed that both T32742468C and G32742603A were located in intron 1 of the SH3-domain GRB2-like 2 (SH3GL2) gene. We conclude that five SNPs, including C1704887T and C1715301T of VIPR-1, T5841629C of DRD2, and T32742468C and G32742603A of SH3GL2, would be useful as markers for breeding to increase chicken EN300.     

Overexpression of Jatropha curcas Defensin (JcDef) Enhances Sheath Blight Disease Resistance in Tobacco

Plant defensins are small, basic, cysteine‐rich peptides, belonging to the antimicrobial peptide superfamily, commonly found in the plant kingdom. In this study, we cloned and characterized a plant defensin gene from Jatropha curcas (JcDef). JcDef carried conserved receptor binding sites and a cysteine motif, and it was phylogenetically grouped together with defensin Ec‐AMP‐D2‐like in Elaeis guineensis. JcDef is localized to cytoplasm and highly expressed in young tissues with fast metabolism such as cotyledons and stem apexes. Transgenic expression of JcDef in tobacco showed enhanced resistance against sheath blight disease caused by R. solani, indicating the antibacterial function.     

杜鹃花属的研究(二)

灌木,高1.5-3米。小枝适度地纤细,当年生者紫色,有鳞斑,约长4-5厘米,直径1-1.5毫米,一年生以上者淡黄色或褐色,无鳞斑。冬芽长圆锥状,鳞片覆瓦状排列,早落。叶薄纸质,狭窄或长圆状椭圆形,先端渐尖或近于钝尖状锐尖,基部楔形或钝形,长4.5-5厘米,宽1.2-2厘米,上面深绿色,有稀疏的鳞斑,下面淡绿色,有鳞斑,彼此间的距离,为其直径的2-3倍,中脉在上而略四陷,在下面稍凸起,侧脉不发育;叶柄有稀疏的鳞斑,长6-8毫米。     

小鼠子宫颈部位输卵管蛋白表达的初步研究

用RT-PCR及免疫印迹法检测证实小鼠子宫颈粘膜上皮细胞具表达输卵管蛋白的能力,宫颈部所获得的输卵管蛋白转录产物, 310到 714的405bp的cDNA片段经序列测定及blast比较表明与输卵管部位表达的输卵管蛋白完全一致(100%)。小鼠子宫颈输卵管蛋白在动情周期的表达波动情况与输卵管粘膜上皮的类似,其表达于小鼠动情期明显增加。Westernblot显示小鼠子宫颈提取物中存在两种不同分子量(60KD,30KD)的输卵管蛋白。原位杂交结果则提示子宫颈粘膜上皮细胞含丰富的输卵管蛋白mRNA信号。通过"原体中风"实验未发现输卵管蛋白在体外对精子活动有影响,其功能尚须进一步分析。     

The DLC-1 -29A/T polymorphism is not associated with nasopharyngeal carcinoma risk in Chinese population

Deleted in liver cancer-1 (DLC-1), encoding a Rho GTPase-activating protein (GAP), is considered as a promising candidate tumor suppressor gene in nasopharyngeal carcinoma (NPC). The single-nucleotide polymorphism (SNP) -29A/T upstream of ATG start codon was found when gene mutation profile of DLC-1 in NPC was analyzed. To evaluate the correlation between SNP -29A/T in the promoter region of DLC-1 gene and risk of NPC, a total of 521 samples from a Chinese population, including 320 healthy individuals and 201 NPC patients, were collected for SNP analysis by PCR-single-strand conformation polymorphism and sequencing. The differences in allele and genotype frequencies between NPC patients and controls were tested using logistic regression statistical method. No significant differences were found in allele or genotype frequencies between NPC patients and controls or among different NPC clinical stages. Hence, our data indicate that the SNP -29A/T of DLC-1 gene is not associated with NPC susceptibility.     

玉米幼苗萎蔫过程中某些理化性质变化的研究

玉米幼苗在暂时性萎蔫期间失水速率相对较慢,可溶性糖,脯氨酸等渗透调度物质的积累较多,ＳＯＤ活性增加,而在永久性萎缩期间失水速率较快,渗透调节物质减少,ＳＯＤ活性下降,在玉米幼苗萎蔫的全过程中,叶绿素,蛋白质含量及ＣＡＴ,ＰＯＤ活性等迅速下降,质膜透性增大,膜脂过氧化加剧。