Origins of bilateral symmetry: Hox and dpp expression in a sea anemone

Over 99% of modern animals are members of the evolutionary lineage Bilateria. The evolutionary success of Bilateria is credited partly to the origin of bilateral symmetry. Although animals of the phylum Cnidaria are not within the Bilateria, some representatives, such as the sea anemone Nematostella vectensis, exhibit bilateral symmetry. We show that Nematostella uses homologous genes to achieve bilateral symmetry: Multiple Hox genes are expressed in a staggered fashion along its primary body axis, and the transforming growth factor-beta gene decapentaplegic (dpp) is expressed in an asymmetric fashion about its secondary body axis. These data suggest that bilateral symmetry arose before the evolutionary split of Cnidaria and Bilateria.     

团头鲂形态发育相关基因HoxB1b的克隆及功能研究

脊椎动物Hox族基因是一类重要的生长和发育调控基因,它编码具有螺旋—转角—螺旋结构的转录因子,能与下游靶基因特定区域结合并激活表达,从而调节脊椎动物胚胎发育过程中前后轴的形态建成。利用cDNA末端快速扩增法(RACE)克隆了团头鲂(Megalobrama amblycephala)HoxB1b基因的全长cDNA序列,并研究了该基因的表达模式。结果表明:(1)团头鲂HoxB1b基因cDNA全长为1 479 bp,其中包括一个编码306个氨基酸残基的921 bp阅读框,聚类分析结果表明,该基因与斑马鱼、红鳍东方鲀、青鳉的相似度分别为89%、45%、40%,在脊椎动物中具有一定的保守性;(2)RT-PCR分析结果显示,HoxB1b在团头鲂胚胎发育过程的各时期均有稳定表达,但在成熟卵中未检测到该基因的表达,表明该基因属非母源表达类型。进一步的整胚原位杂交结果显示,HoxB1b在团头鲂不同时期胚胎存在明显的空间表达差异,受精后20 h(20 hours post fertilization,20hpf)胚胎主要在后脑表达,受精后40 h(40hpf)胚胎除了在后脑表达外,在胸鳍也检测到表达;(3)HoxB1b基因在团头...     

生物固氮基因簇结构与进化研究进展

在固氮菌基因组中,固氮相关基因都是作为一个或几个基因簇存在,是细菌生物固氮的遗传基础。这其中包括固氮酶结构基因nifHDK,以及参与电子转运和铁钼辅因子合成及组装的其他相关基因。对不同菌中固氮基因簇的结构和进化进行了简要的比较分析。比较所有已测序固氮菌中的固氮基因簇,发现均至少含有六个保守基因:nifH、nifD、nifK、nifE、nifN和nifB,并且这6个基因在所有已鉴定的系统中都是固氮所必需的。尽管在不同种类的固氮微生物中,固氮基因簇的构成及组织模式有所不同,但是它们在结构、催化机制和系统进化上紧密相关。同时也对固氮基因的研究方向提出了展望。旨在为今后进一步研究生物固氮机制,了解固氮微生物的进化,扩展生物固氮多样性提供理论基础。     

The ecoresponsive genome of Daphnia pulex

We describe the draft genome of the microcrustacean Daphnia pulex, which is only 200 megabases and contains at least 30,907 genes. The high gene count is a consequence of an elevated rate of gene duplication resulting in tandem gene clusters. More than a third of Daphnia's genes have no detectable homologs in any other available proteome, and the most amplified gene families are specific to the Daphnia lineage. The coexpansion of gene families interacting within metabolic pathways suggests that the maintenance of duplicated genes is not random, and the analysis of gene expression under different environmental conditions reveals that numerous paralogs acquire divergent expression patterns soon after duplication. Daphnia-specific genes, including many additional loci within sequenced regions that are otherwise devoid of annotations, are the most responsive genes to ecological challenges.     

Hox10 and Hox11 genes are required to globally pattern the mammalian skeleton

Mice in which all members of the Hox10 or Hox11 paralogous group are disrupted provide evidence that these Hox genes are involved in global patterning of the axial and appendicular skeleton. In the absence of Hox10 function, no lumbar vertebrae are formed. Instead, ribs project from all posterior vertebrae, extending caudally from the last thoracic vertebrae to beyond the sacral region. In the absence of Hox11 function, sacral vertebrae are not formed and instead these vertebrae assume a lumbar identity. The redundancy among these paralogous family members is so great that this global aspect of Hox patterning is not apparent in mice that are mutant for five of the six paralogous alleles.     

Metabolic diversification--independent assembly of operon-like gene clusters in different plants

Operons are clusters of unrelated genes with related functions that are a feature of prokaryotic genomes. Here, we report on an operon-like gene cluster in the plant Arabidopsis thaliana that is required for triterpene synthesis (the thalianol pathway). The clustered genes are coexpressed, as in bacterial operons. However, despite the resemblance to a bacterial operon, this gene cluster has been assembled from plant genes by gene duplication, neofunctionalization, and genome reorganization, rather than by horizontal gene transfer from bacteria. Furthermore, recent assembly of operon-like gene clusters for triterpene synthesis has occurred independently in divergent plant lineages (Arabidopsis and oat). Thus, selection pressure may act during the formation of certain plant metabolic pathways to drive gene clustering.     

鸭发育早期下丘脑-垂体生长轴相关基因mRNA的表达特异性分析

【目的】选择生长速度不同的高邮鸭和金定鸭为试验模型,3种不同品种鸭胚胎期和出雏早期下丘脑垂体生长轴相关基因的表达规律及其与体重和肝重的相关性。【方法】采用实时荧光定量PCR方法研究鸭13、17、21、25、27胚龄和出雏后7日龄下丘脑生长激素释放激素（growth hormone release hormone,GHRH）与生长抑素（somatostatin,SS）、垂体生长激素（growth hormone,GH）和肝脏生长激素受体（growth hormone receptor,GHR）与胰岛素样生长因子（insulin-like growth factors,IGFs） mRNA的表达规律。【结果】证实鸭下丘脑GHRH与SS、垂体GH和肝脏GHR与IGF-I在13胚龄已有表达;除了SS在鸭发育早期维持一个低表达状态外,其它的4种基因均呈现极显著的品种和时间特异性;除了GH外,发现鸭早期发育过程中GHRH、GHR和IGF-I mRNA的表达受到品种和日龄的交互作用的极显著影响。与鸡以往的研究相比,禽类胚胎期下丘脑垂体生长轴相关基因mRNA的表达存在着种属差异。本试验发现鸭早期发育过程中,体重和肝重的变化也呈现极显著的品种和时间特异性,且与下丘脑垂体相关基因的表达呈现不同程度的线性相关。【结论】结果提示下丘脑垂体生长轴基因 mRNA的表达可能在鸭早期发育过程中发挥着重要作用,遗传背景的差异可以导致鸭发育早期体重的差异生长和相关基因的差异表达。     

Hoxc13 Expression Pattern in Cashmere Goat Skin During Hair Follicle Development

Hoxc13 has an important role in controlling hair formation. In this study, we examine the Hoxc13 RNA expression pattern of skin during embryo development. The result indicated that changes of the Hoxe13 gene expression and thickness of skin have a similar trend during hair follicle morphogenesis. In interpreting these results, we investigated whether the regulation motifs is in Hoxc13 intron, which is a 5.4 kb fragment. To blast with other mammals, we found a very conservative region in all mammal animals and two regions in livestock, such as cow, sheep, horse, dog, and so on, which are not in other Hox genes. We have examined putative pre-miRNA in this region, providing an entry point for elucidating currently unknown mechanisms that are required for regulating quantitative levels of Hoxc13 gene expression.     

Smed-betacatenin-1 is required for anteroposterior blastema polarity in planarian regeneration

Planarian flatworms can regenerate heads at anterior-facing wounds and tails at posterior-facing wounds throughout the body. How this regeneration polarity is specified has been a classic problem for more than a century. We identified a planarian gene, Smed-betacatenin-1, that controls regeneration polarity. Posterior-facing blastemas regenerate a head instead of a tail in Smed-betacatenin-1(RNAi) animals. Smed-betacatenin-1 is required after wounding and at any posterior-facing wound for polarity. Additionally, intact Smed-betacatenin-1(RNAi) animals display anteriorization during tissue turnover. Five Wnt genes and a secreted Frizzled-related Wnt antagonist-like gene are expressed in domains along the anteroposterior axis that reset to new positions during regeneration, which suggests that Wnts control polarity through Smed-betacatenin-1. Our data suggest that beta-catenin specifies the posterior character of the anteroposterior axis throughout the Bilateria and specifies regeneration polarity in planarians.     

林木遗传转化及其潜在生态风险研究进展

林木遗传转化技术近些年来得到了较大的发展,集中表现在转基因技术和目的基因两个方面。前者主要表现为多种措施联合使用,提高了遗传转化率;后者主要表现为应用于林木遗传转化的目的基因数量逐年增多,从原来的抗虫基因发展到现在的多个目的基因:木质素改良基因、花发育相关基因、生长相关基因及抗污染基因等;这些基因在不同的树种均有遗传转化成功的例子。转基因林木潜在生态风险研究主要集中在:基因的水平转移、基因的垂直流动及转基因对昆虫的影响等方面。初步的试验结果和理论分析认为,转基因林木的大田释放具有一定的生态潜在风险,需要对这种风险进行更深入、精确的评估。林木遗传工程及其生态安全性的研究需进一步努力解决的问题包括:1)林木遗传转化效率相对较低,特别是针叶树种,建立转基因体系还比较困难;2)林木树体高大,生长周期很长,外源基因在转基因植株中的时空表达特性还有待继续深入研究;3)比较系统的转基因林木田间释放和生态安全性试验数量还很少。     

Shaping the vertebrate body plan by polarized embryonic cell movements

Polarized cell movements shape the major features of the vertebrate body plan during development. The head-to-tail body axis of vertebrates is elongated in embryonic stages by "convergent extension" tissue movements. During these movements cells intercalate between one another transverse to the elongating body axis to form a narrower, longer array. Recent discoveries show that these polarized cell movements are controlled by homologs of genes that control the polarity of epithelial cells in the developing wing and eye of the fruit fly, Drosophila.     

水稻中富含亮氨酸的重复序列和核苷酸结合位点(LRR-NBS)基因家族的生物信息学分析

 采用HMM(HiddenMarkovModel) ,对源于日本晴的粳稻 (国际水稻测序计划 ,IRGSP)基因组和 9311的籼稻基因组 (北京华大 ,BGI)的蛋白质数据库进行了搜索 ,分别获得了 32 5和 344个富含亮氨酸的重复序列和核苷酸结合位点 (leucinerichrepeat-nucleotidebindingsite ,LRR -NBS)类的抗病基因的蛋白序列 ,并得到了与这些蛋白相应的cDNA序列。对粳稻蛋白功能结构域的分析表明 ,多个蛋白具有与植物防卫反应相关的结构域 ,还发现多个蛋