链霉菌Streptomyces antibioticus NRRL 8167中Naphthgeranine A生物合成基因簇的分析鉴定

【背景】微生物来源的天然产物是小分子药物或药物先导物的重要来源。对链霉菌Streptomyces antibioticus NRRL 8167的基因组分析显示,其包含多个次级代谢产物的生物合成基因簇,具有产生多种新化合物的潜力。【目的】对链霉菌S. antibioticus NRRL 8167中次级代谢产物进行研究,以期发现结构新颖或生物活性独特的化合物,并对相应产物的生物合成基因簇和生物合成途径进行解析。【方法】利用HPLC图谱结合特征性紫外吸收和LC-MS方法,排除S. antibioticus NRRL 8167产生的已知化合物,确定具有特殊紫外吸收的化合物作为挖掘对象,然后利用正、反相硅胶柱色谱、高效液相色谱等技术对次级代谢产物进行分离纯化,分离化合物。利用质谱及核磁共振光谱技术对化合物结构进行解析和鉴定;提取链霉菌S. antibioticus NRRL 8167基因组DNA,利用PacBio测序平台进行基因组测序;利用生物信息学对基因组进行注释,并对合成该化合物的基因簇进行定位分析,推导其生物合成途径。【结果】确定这个化合物是NaphthgeranineA,属于聚酮类化合物。全基因组序列分析发现S.antibioticusNRRL8167基因组含有28个次级代谢产物生物合成基因簇,其中基因簇20可能负责Naphthgeranine A的生物合成,并对其生物合成途径进行了推导。【结论】基于紫外吸收光谱和质谱特征,从S. antibioticus NRRL 8167菌株的发酵提取物中分离鉴定了一个聚酮类化合物Naphthgeranine A。该菌株的全基因组测序为其生物合成基因簇的鉴定提供了前提,对Naphthgeranine A生物合成基因簇和生物合成途径的推测为进一步研究这个化合物的生物合成机制奠定了基础。     

拟环纹狼蛛对褐飞虱的捕食作用及其模拟模型的研究 Ⅳ.单种捕食者-两种猎物系统的模拟模型及其稳定性分析

本文提出了描述单种捕食者-两种猎物系统的模拟模型。在功能反应和选择捕食实验的基础上,应用数值模拟方法分析了模型中各参数对稳定性的影响,以及拟环纹狼蛛-褐飞虱、稻纵卷叶螟三物种系统的稳定性。     

Immune-related microRNAs are abundant in breast milk exosomes

Breast milk is a complex liquid rich in immunological components that affect the development of the infant's immune system. Exosomes are membranous vesicles of endocytic origin that are found in various body fluids and that can mediate intercellular communication. MicroRNAs (miRNAs), a well-defined group of non-coding small RNAs, are packaged inside exosomes in human breast milk. Here, we identified 602 unique miRNAs originating from 452 miRNA precursors (pre-miRNAs) in human breast milk exosomes using deep sequencing technology. We found that, out of 87 well-characterized immune-related pre-miRNAs, 59 (67.82%) are presented and enriched in breast milk exosomes (P < 10(-16), χ(2) test). In addition, compared with exogenous synthetic miRNAs, these endogenous immune-related miRNAs are more resistant to relatively harsh conditions. It is, therefore, tempting to speculate that these exosomal miRNAs are transferred from the mother's milk to the infant via the digestive tract, and that they play a critical role in the development of the infant immune system.     

Genetic Variability of PRNP in Chinese Indigenous Goats

Polymorphism of the prion protein gene (PRNP) is usually associated with scrapie susceptibility or resistance. To determine the variability of PRNP in Chinese indigenous goat breeds, we isolated genomic DNA from goat blood and amplified and sequenced the coding region of the gene. We identified 10 polymorphic sites that gave rise to 28 haplotypes. Clear frequency differences were found between northern and southern breeds and confirmed by genetic distance analysis, except for the Tangshan dairy goat. Phylogeographic analysis supported the idea that northern and southern breeds might be considered separate clusters, except for the Tangshan dairy goat. The finding of significant differences in allele distribution in northern and southern goats, especially if involved in modulating resistance/susceptibility, needs to be carefully considered for the feasibility of selection plans for resistance to scrapie.     

热玫瑰小双孢菌来源的丙酮酸磷酸双激酶的表达及应用

以热玫瑰小双孢菌基因组DNA为模板, 通过PCR扩增得到了编码PPDK的基因, 将此基因片段插入到表达载体pET28a(+)中构建得到了重组表达质粒pET28a(+)-PPDK, 将重组表达质粒pET28a(+)-PPDK转化到大肠杆菌BL21(DE3)中, 经过IPTG诱导, 重组菌成功表达了N端带有6-His Tag的重组PPDK。经SDS-PAGE分析, 重组PPDK单体分子量为101 kD。经过镍亲和层析和超滤后, 重组PPDK蛋白基本达到电泳纯, 并被成功应用于焦测序中。     

Promoting human embryonic stem cell renewal or differentiation by modulating Wnt signal and culture conditions

We previously showed that Wnt3a could stimulate human embryonic stem （hES） cell proliferation and affect cell fate determination. In the absence of feeder cell--derived factors, hES cells cultured under a feeder-free condition survived and proliferated poorly. Adding recombinant Wnt3a in the absence of feeder cell derived-factors stimulated hES cell proliferation but also differentiation. In the present study, we further extended our analysis to other Wnt ligands such as Wntl and Wnt5a. While Wntl displayed a similar effect on hES cells as Wnt3a, Wnt5a had little effect in this system. Wnt3a and Wntl enhanced proliferation of undifferentiated hES cells when feeder-derived self-renewal factors and bFGF are also present. To explore the possibility to promote the proliferation of undifferentiated hES cells by activating the Wnt signaling, we overexpressed Wnt3a or Wntl gene in immortalized human adult fibroblast （HAFi） cells that are superior in supporting long-term growth of undifferentiated hES cells than primary mouse embryonic fibroblasts. HAFi cells with or without a Wnt tmnsgene can be propagated indefinitely. Over-expression of the Wnt3a gene significantly enhanced the ability of HAFi feeder cells to support the undifferentiated growth of 3 different hES cell lines we tested. Co-expression of three commonly-used drug selection genes in Wnt3a-overpressing HAFi cells further enabled us to select rare hES clones after stable transfection or transduction. These immortalized engineered feeder cells （W3R） that co-express growth-promoting genes such as Wnt3a and three drug selection genes should empower us to efficiently make genetic modified hES cell lines for basic and translational research.     

Toward a theory for diversity gradients: the abundance–adaptation hypothesis

The abundance–adaptation hypothesis argues that taxa with more individuals and faster generation times will have more evolutionary ‘experiments’ allowing expansion into, and diversification within, novel habitats. Thus, as older taxa have produced more individuals over time, and smaller taxa have higher population sizes and faster generation times, the Latitudinal Diversity Gradients (LDGs) of these clades should show shallower slopes. We describe the LDGs for archaea, bacteria, fungi, invertebrates and trees from six North American forests. For three focal groups – bacteria, ants, and trees – older taxa had shallower LDG slopes than the more recent, terminal taxa. Across 12 orders of magnitude of body mass, LDG slopes were steeper in larger taxa. The slopes of LDGs vary systematically with body size and clade age, underscoring the non‐canonical nature of LDGs. The steepest LDG slopes were found for the largest organisms while the smallest, from bacteria to small litter‐soil invertebrates, have shallower‐ to zero‐slope LDGs. If tropical niche conservatism is the failure of clades to adapt to, and diversify in temperate habitats, then the steep LDGs of chordates and plants likely arise from the decreased ability of clades with large individuals to adapt to the multiple challenges of extra‐tropical life.