环境对产毒性大肠杆菌肠毒素表达的影响

通过体外试验,探讨一些与人体肠道微环境有关因素的变化对ＥＴＥＣ主要毒力因子肠毒素产生的影响。研究结果表明,细菌培养基的ｐＨ、渗透浓度、气体组成及温度的不同均可影响ＥＴＥＣ肠毒素的产生,而且ＬＴ与ＳＴ对有关环境因素的反应有所不同,一些与肠道环境有关环境条件的变化可影响ＥＴＥＣ肠毒素的表达,提示机体肠道微环境的变化可能与ＥＴＥＣ的致病有关。     

产肠毒素大肠杆菌的热敏肠毒素B亚基(LT-B)和耐热肠毒素(ST)基因融合及其表达

采用基因重组技术构建了表达产肠毒素大肠杆菌(ETEC)的耐热肠毒素(ST)基因和热敏肠毒素B亚基(LT-B)基因融合抗原的疫苗候选株。将ST基因的5’端与LT-B基因的3’端连接,并置于同一阅读框。编码ST的基因是通过PCR从pSLM004质粒中扩增得到的,含有ST的pro序列(其编码ST前体的pro区域),并应用寡核苷酸定点突变技术将编码ST的第14位氨基酸残基发生突变,使ST的第14位氨基酸残基Ala突变为Leu。在所构建的结构中,于LT-B和proST之间分别插入了不同长度的氨基酸Linkers。表达的融合多肽同时具有ST和LT-B的抗原性,并保留结合GM-1神经节苷脂的能力,且无LT和ST的生物毒性。表达的融合蛋白免疫动物,能诱导产生相应的特异性抗体。     

利用离体叶片鉴定杨树耐盐潜力

以受体杨树107和转基因杨树18-1的一年生枝条为材料,采用Hoagland营养液水培方法,添加不同浓度的NaCl,检测二者植株生长以及叶中Na＋和K＋含量的变化。结果表明,在0.6%NaCl处理下18-1生根率明显高于107,生物量较大,叶片中Na＋积累量是107的1.45倍左右。以107和18-1离体叶片为材料,NaCl处理下测定其生理活性指标,发现18-1叶盘的失绿速度和相对电导率都显著低于107叶盘。把离体叶片接种在改良MS培养基上,1.2%NaCl处理可使107叶盘几乎停止伸长,细胞大小不再增加;而18-1叶盘培养7天后伸长了近50%。以上结果表明利用离体叶片可以鉴定出不同基因型杨树的耐盐潜力。     

利用离体叶片鉴定杨树耐盐潜力

以受体杨树107和转基因杨树18-1的一年生枝条为材料, 采用Hoagland营养液水培方法, 添加不同浓度的NaCl, 检测二者植株生长以及叶中Na⁺和K⁺含量的变化。结果表明, 在0.6%NaCl处理下18-1生根率明显高于107, 生物量较大, 叶片中Na⁺积累量是107的1.45倍左右。以107和18-1离体叶片为材料, NaCl处理下测定其生理活性指标, 发现18-1叶盘的失绿速度和相对电导率都显著低于107叶盘。把离体叶片接种在改良MS培养基上, 1.2%NaCl处理可使107叶盘几乎停止伸长, 细胞大小不再增加; 而18-1叶盘培养7天后伸长了近50%。以上结果表明利用离体叶片可以鉴定出不同基因型杨树的耐盐潜力。     

SCABP8/CBL10, a putative calcium sensor, interacts with the protein kinase SOS2 to protect Arabidopsis shoots from salt stress

The SOS (for Salt Overly Sensitive) pathway plays essential roles in conferring salt tolerance in Arabidopsis thaliana. Under salt stress, the calcium sensor SOS3 activates the kinase SOS2 that positively regulates SOS1, a plasma membrane sodium/proton antiporter. We show that SOS3 acts primarily in roots under salt stress. By contrast, the SOS3 homolog SOS3-LIKE CALCIUM BINDING PROTEIN8 (SCABP8)/CALCINEURIN B-LIKE10 functions mainly in the shoot response to salt toxicity. While root growth is reduced in sos3 mutants in the presence of NaCl, the salt sensitivity of scabp8 is more prominent in shoot tissues. SCABP8 is further shown to bind calcium, interact with SOS2 both in vitro and in vivo, recruit SOS2 to the plasma membrane, enhance SOS2 activity in a calcium-dependent manner, and activate SOS1 in yeast. In addition, sos3 scabp8 and sos2 scabp8 display a phenotype similar to sos2, which is more sensitive to salt than either sos3 or scabp8 alone. Overexpression of SCABP8 in sos3 partially rescues the sos3 salt-sensitive phenotype. However, overexpression of SOS3 fails to complement scabp8. These results suggest that SCABP8 and SOS3 are only partially redundant in their function, and each plays additional and unique roles in the plant salt stress response.     

The association between C-159T polymorphism in CD14 gene and susceptibility to tuberculosis: a meta-analysis

The association between CD14 gene C-159T polymorphism and tuberculosis (TB) susceptibility remains inconclusive. To derive a more precise estimation of the correlation, we performed a meta-analysis summarize the possible at a systematic manner. PubMed, HighWire and ScienceDirect databases covering all papers (up to November 2012) were searched. Statistical analyses were conducted by Rev-Man and STATA. Random- and fixed-effect models were used to estimate pooled odds ratios (ORs) and 95 % confidence intervals (CIs), based on between-study heterogeneity. Eight published case–control studies investigating the relationship between C-159T polymorphism in CD14 gene and TB susceptibility were included. Results showed that individuals with T allele have an increased risk of TB compared with those with C allele (OR (95 % CI) was 1.52 (1.11, 2.08) for TT vs. TC + CC, P < 0.001; 1.27 (1.01, 1.61) for T vs. C, P = 0.04). When stratified by ethnicity, variant TT homozygote carriers had an 86 % increased risk of TB in Asians (OR (95 % CI) was 1.86 (1.57, 2.20) for TT vs. TC + CC, P < 0.001), but not in Caucasians (OR (95 % CI) was TT vs. TC + CC: OR = 0.78, 95 % CI = 0.51–1.21, P = 0.61). This meta-analysis suggests that C-159T polymorphism in CD14 gene is associated with increased risk of TB, especially in Asians, but not in Caucasians.     

Dual effects of sodium butyrate on hepatocellular carcinoma cells

Sodium butyrate (NaBu), a histone deacetylase inhibitor, has been shown to inhibit cell growth, induce cell differentiation and apoptosis in multiple cell lines. In present study, we revealed the dual effects of NaBu in regulating hepatocellular carcinoma (HCC) cells. In two different HCC cell lines, SK-Hep1 and SMMC-7721, low concentrations of NaBu induced a significant increase in cell growth ratio and S-phase cell percentage, accompanied by a reduced p21 Cip1 expression at both mRNA and protein levels, while dissimilarly, high concentrations of NaBu inhibited cell growth and induced G1 arrest through up-regulation of p21 Cip1 and p27 Kip1 protein expression. The reduction of p45 Skp2 expression further indicated that the ubiquitin-mediated protein degradation might play a role in NaBu-induced up-regulation of p21 Cip1 and p27 Kip1. Moreover, the high concentration of NaBu was also able to trigger HCC cell apoptosis. Taken together, these results demonstrate the distinct effects of NaBu at different dosages. This finding may contribute to develop more effective tumor therapeutic protocols of NaBu in HCC.     

Comparative study of QTLs for agronomic traits of rice (Oriza sativa L.) between salt stress and nonstress environment

Genotype-by-environment interactions (GxE) are commonly observed for quantitative traits. In the present study, a doubled haploid (DH) population and its genetic linkage map were used to comparatively study QTLs in salt stress and nonstress environments. A total of 24 QTLs were detected for five agronomic traits, which were distributed on all the chromosomes except 9 and 11. Under the salt stress, nine (37.5%) QTLs were detected, including one for 1 000-grain weight (GW), two for heading date (HD), one for plant height (PH), two for grains per panicle (GPP), and three for effective tillers (ET), while in the nonstress environment, 17 QTLs (70.8%) were detected, including five for GW, six for HD, three for PH, two for GPP, and one for ET. Two QTLs (8.3%) were consistently detected in both environments. One was identified on chromosome 4 for HD and the other on Chr.6 for GPP. Furthermore, three regions carrying multiple QTLs were identified on chromosomes 1, 4 and 8 respectively. For example, on chromosome