Genome-wide high-resolution mapping and functional analysis of DNA methylation in arabidopsis.

Cytosine methylation is important for transposon silencing and epigenetic regulation of endogenous genes, although the extent to which this DNA modification functions to regulate the genome is still unknown. Here we report the first comprehensive DNA methylation map of an entire genome, at 35 base pair resolution, using the flowering plant Arabidopsis thaliana as a model. We find that pericentromeric heterochromatin, repetitive sequences, and regions producing small interfering RNAs are heavily methylated. Unexpectedly, over one-third of expressed genes contain methylation within transcribed regions, whereas only approximately 5% of genes show methylation within promoter regions. Interestingly, genes methylated in transcribed regions are highly expressed and constitutively active, whereas promoter-methylated genes show a greater degree of tissue-specific expression. Whole-genome tiling-array transcriptional profiling of DNA methyltransferase null mutants identified hundreds of genes and intergenic noncoding RNAs with altered expression levels, many of which may be epigenetically controlled by DNA methylation.

灵长类泌乳刺激素基因的插曲式进化

采用PCR 方法从4 个灵长目物种中获得了泌乳刺激素(Prolactin, PRL)基因的第2~5 外显子的序 列, 结合GenBank 中已有的序列, 计算了PRL 基因在灵长目中的氨基酸替换速率. 对异义替换速率和 同义替换速率进行比较的结果显示, 在灵长目进化的过程中未发现任何一个枝系有正选择作用的迹象. 此外, 用最大似然(Maximum-Likelihood, ML)法没有检验到任何一个受到正选择作用的位点; 在快速 进化时期内发生的所有32 个氨基酸替换中, 只有2 个位点包含在功能重要的40 个氨基酸之内, 提示所 发生的氨基酸替换主要集中在功能上并不是很重要的位点上. 此外, 在PRL 基因的快速进化过程中, PRL 的部分功能被胎盘泌乳刺激素(placental lactogen, PL)所替代. 基于以上原因, 推测发生在灵长目 PRL 基因的快速进化很可能是选择压力的放松, 而不是正选择作用的结果.

利用胚胎工程技术提高我国奶产量

近年来动物胚胎程技术发展迅速,并逐步在畜牧业中推广运用。胚胎移植是目前应用最为广泛的现代繁育技术。经过几十年的发展,国内胚胎移植相关技术已相当成熟,可以多种形式满足不同市场的需求。同时,由于中国奶牛种质较差,奶业基础相对薄弱,需大力繁育高产优质奶牛,在减少饲养数量的同时提高牛奶产量和质量,提高饲养经济效益,胚胎工程技术对发展国内奶业意义重大。总之,利用胚胎工程技术提高我国奶产量已经具备条件,而且是必由之路。

中国大陆白腹鼠属的分支系统发育研究

　运用Hennig 的分支系统学原理和方法, 对分布于中国大陆的白腹鼠属7 个种的部分外部及头骨形态学特征 进行性状数据分析, 结合应用Paup 和Hennig 86 两种分支系统学软件对它们之间的系统发育关系进行研究。结果表 明: 安氏白腹鼠N. andersoni 和川西白腹鼠N. excelsior 亲缘关系较近, 二者聚在一起, 组成了Musser (1981) 的安 氏白腹鼠种组N. andersoni2Division ; 另外刺毛鼠N. f ulvescens 和褐尾鼠N. cremoriventer 的亲缘关系最近, 二者先 聚在一起, 再与社鼠N. conf ucianus 聚在一起, 形成了安氏白腹鼠种组的姐妹群; 而梵鼠N. brahma 是上述5 种白 腹鼠组成类群的姐妹群, 灰腹鼠N. eha 则与前6 种白腹鼠组成类群互为姐妹群。

污水处理中的人工湿地强化技术研究

人工湿地作为一种新型污水生态处理工艺受到越来越广泛的重视,在生活污水、特种工业废水、采矿污水、农业和畜牧业污水以及水产养殖废水等处理中得到了广泛的应用。但是其本身的局限却限制了它在高浓度废水、某些工业废水处理等方面的应用,在寒冷地区的应用也受到限制。本研究分析了一些强化技术(如湿地内部要素强化、工艺强化和工程强化等)在提高人工湿地的净化效能以及扩大其应用范围的可能性。

猪囊尾蚴铜/锌超氧化物歧化酶(Cu/ZnSOD)基因的克隆和表达

目的克隆猪囊尾蚴胞质含铜/锌的超氧化物歧化酶基因(Cu/ZnSOD),并比较其与其它寄生蠕虫相应基因结构的相似性。方法通过获取其它生物Cu/ZnSOD基因的保守区域,设计保守引物,用于扩增该寄生虫的Cu/ZnSOD基因。结果Cu/ZnSOD基因编码一15.6kDa的蛋白,该蛋白的推导序列中含有这类酶的活性和二级结构所需要的所有保守的氨基酸残基,并且与其它寄生虫的相应序列有高达70.6%的相似度。抑制剂研究试验表明所克隆的SOD属于Cu/ZnSOD,该蛋白在大肠杆菌中得以成功表达,表达产物具有SOD活性。免

ApcD is necessary for efficient energy transfer from phycobilisomes to photosystem I and helps to prevent photoinhibition in the cyanobacterium Synechococcus sp PCC 7002

Phyrobilisomes (PBS) are the major light-harvesting, protein-pigment complexes in cyanobacteria and red algae. PBS absorb and transfer light energy to photosystem (PS) II as well as PS I, and the distribution of light energy from PBS to the two photosystems is regulated by light conditions through a mechanism known as state transitions. In this study the quantum efficiency of excitation energy transfer from PBS to PS I in the cyanobacterium Synechococcus sp. PCC 7002 was determined, and the results showed that energy transfer from PBS to PS I is extremely efficient. The results further demonstrated that energy transfer from PBS to PS I occurred directly and that efficient energy transfer was dependent upon the allophycocyanin-B alpha subunit, ApcD. In the absence of ApcD, cells were unable to perform state transitions and were trapped in state 1. Action spectra showed that light energy transfer from PBS to PS I was severely impaired in the absence of ApcD. An apcD mutant grew more slowly than the wild type in light preferentially absorbed by phyrobiliproteins and was more sensitive to high light intensity. On the other hand, a mutant lacking ApcF, which is required for efficient energy transfer from PBS to PS II, showed greater resistance to high light treatment. Therefore, state transitions in cyanobacteria have two roles: (1) they regulate light energy distribution between the two photosystems; and (2) they help to protect cells from the effects of light energy excess at high light intensities. (C) 2009 Elsevier B.V. All rights reserved.

Investigation on intake, accumulation and toxicity of microcystins to silver carp

Daily intake and accumulation of microcystins (MCYSTs, MCs) in silver carp (Hypophthalmichthys molitrix) were investigated under lab conditions by feeding the fish exclusively with fresh toxic Microcystis bloom at a density of 6 x 10(9) algal cells L-1. The medial lethal dose (LD50) of microcystin-LR to silver carp was estimated to be 270 mu g kg(-1) body-weight, underlining its strong resistance to toxic Microcystis bloom. It can survive after being ingested with high doses of microcystins (about 10 mg kg(-1)) during the 28-days feeding experiment. Enzyme-linked immuno-sorbent assay results show that microcystin concentrations in muscle and liver are 1.57 +/- 0.31 mu g kg(-1) and 4.28 +/- 1.64 mg kg(-1) fresh weight. The former is much lower than the World Health Organization limit recommended for human consumption. These results suggest that silver carps can be widely used in cyanobacterial bloom control, and consumption of fish muscles is safe for human beings.

Numerical study of sub-wavelength plasmonic waveguide

The authors present an analysis of a plasmonic waveguide, simulated using a two-dimensional finite-difference time-domain technique. With the surface structures located on the surface of the metal, the device is able to confine and guide light waves in a sub-wavelength scale. And two waveguides can be placed within 150 nm (similar to 6% of the incident wavelength) that will helpful for the optoelectronic integration. Within the 20 mu m simulation region, it is found that the intensity of the guided light at the interface is roughly two to four times the peak intensity of the incident light, and the propagation length can reach approximately 40 Pm at the wavelength of 2.44 mu m. (c) 2007 Elsevier B.V. All rights reserved.

基于一阶迁移系统的限界模型检测工具实现

基于布尔可满足性(SAT)的限界模型检测是一种高效的模型检测方法，它具有快速查错，反例最小化等特点，已经成为学术界和工业界关注的热点。近些年出现了很多集成限界模型检测算法的验证工具，如ITC-IRST、卡内基梅隆大学(CMU)等多家科研机构联合开发的NuSMV工具；加利福尼亚大学伯克莱分校(UC Berkeley)、科罗拉多大学博尔德分校(CU Boulder)联合开发的VIS工具等。因此目前对于限界模型检测方法的研究和相关工具的设计与开发具有重要而广泛的意义。在进行限界模型检测的建模过程中，不同的工具采用了自定义的建模语言。如经典工具SPIN采用的建模语言是Promela语言，NuSMV采用的是自定义的NuSMV语言。随着系统验证规模的不断增大，建模语言的特点将会直接影响到建模的效率。例如采用NuSMV语言去建立一个网络通信协议模型会显得比较复杂和耗时，应用NuSMV语言去描述一个简单的数据链路层网络协议ABP协议(Alternating Bit Protocol)就不如采用Promela语言去描述显得直观和自然。 为了简化在限界模型检测过程中模型的建立过程，本文给出了一种采用基于一阶迁移系统语言描述的模型建立方法，并在一阶迁移系统语言中实现了通道的功能，从而增强了描述能力。在此基础上完成了一个以基于插值和k步归纳限界验证算法为核心的模型检测工具(BMCF)。最后利用该工具对常见的互斥协议，简单数据传输协议的性质进行了分析与验证。结果表明，利用该工具对系统进行建模具有方便直观的特点，并借助实现的验证算法能高效的检验安全性质的正确性，如果性质不成立工具会给出反例提示。