Phosphorylated Glycans Produced from Nonreducing Mono- and Oligosaccharides by the Action of P2O5 in Dimethyl Sulfoxide,and Their Interactions with Concanavalin A

The action of P₂O₅ in DMSO on methyl α-d-glucopyranoside, sucrose and trehalose afforded nondializable, phosphorylated glycans in 6~34% yields. Polysucrose has a molecular weight of ~9,500. The synthetic glycans consist of carbohydrate (46~59%) and P (11.4~13.1%) and show reducing sugar values (5.0~30.8%). The alkaline hydrolysis of polysucrose was accompanied with a depolymerization and afforded sugar phosphates and oligosaccharides. The periodate oxidation gave formic acid (0.15~0.34 mole) and formaldehyde (0.07~0.17 mole/monosaccharide residue). The methylation study indicated their variously branched structures. 2,3,4,6-Tetra-O-methyl-d-glucose was found in only 0.7 ~3.2% yields, and this is in agreement with their weak precipitation reactions with Con A. It is considered that the glycans are produced from nonreducing mono- and oligosaccharides by dehydration, transglycosidation and esterification with phosphate.     

表油菜素内酯对拟南芥细胞分化的影响

研究了表油菜素内酯（ｅｐｉ－ＢＲ）对拟南芥细胞体外分化的影响．表明ｅｐｉ－ＢＲ不仅能促进愈伤组织的增殖,而且还能有效地诱导愈伤组织转绿,继而分化绿芽和长成小植株,其诱导频率高达７０％以上。电镜观察表明,ｅｐｉ－ＢＲ诱导的转绿细胞中的叶绿体发育正常。     

A Transient RNA Interference Assay System Using Arabidopsis Protoplasts

Double-stranded RNA (dsRNA) induces sequence-specific gene silencing in eukaryotes through a process known as RNA interference (RNAi). RNAi is now used as a powerful tool for functional genomics in many eukaryotes, including plants. We herein report a dsRNA-mediated transient RNAi assay system using protoplasts from Arabidopsis mesophyll cells and suspension-cultured cells (cell line T87). Introduction of dsRNA into protoplasts led to marked silencing of target transgenes. Our assay system would provide a convenient and efficient way to induce RNAi in protoplasts of the model plant Arabidopsis thaliana.     

利用激光扫描共聚焦显微镜研究植物细胞发育形态学变化

通过激光扫描共聚焦显微镜,利用不同种类(波长)的激光研究植物细胞发育形态学变化。结果表明,利用紫外激光(351 nm)扫描可以清楚地观察到拟南芥叶片表皮细胞的形态及其变化,在已分化的叶片表皮上可观察到包括“铺垫”表皮细胞(epidermal pavement cells)、气孔保卫细胞(guard cell)、气孔伴胞(subsidiarycells)、表皮毛细胞(trichomes)和表皮毛的足细胞(socket cells)等多种形态不同的细胞种类;利用蓝光激光(488nm)辅助曙红浅染,可清晰地显示出拟南芥根生长区内部的各种原始细胞,包括静止区(quiescent center)细胞、皮层/内皮层原始细胞(cortex/endodermal initial cell)、表皮/根冠原始细胞(epidermal/root cap initial cell)和中柱/根冠原始细胞(columella/root cap initial cell)等。利用双光子激光(800 nm)连续扫描30 s可以诱发叶绿体产生自发荧光,并可观察到叶绿体在叶肉细胞中的运动轨迹。结果说明激光扫描共聚焦显微镜在植物细胞形态及发育研究上具有独特的功能。     

Cryptic population genetic structure: the number of inferred clusters depends on sample size

Clustering methods have been used extensively to unravel cryptic population genetic structure. We investigated the effect of the number of individuals sampled in each location on the resulting number of clusters. Our study was motivated by recent results in Arabidopsis thaliana: studies in which more than one individual was sampled per location apparently have led to a much higher number of clusters than studies where only one individual was sampled in each location, as is generally done in this species. We show, using computer simulations and microsatellite data in A. thaliana, that the number of sampled individuals indeed has a strong impact on the number of resulting clusters. This effect is smaller if the sampled populations have a hierarchical structure. In most cases, sampling 5–10 individuals per population should be enough. The results argue for abandoning the concept of ‘accessions’ in partially selfing organisms.     

Simple Identification of Transgenic Arabidopsis Plants Carrying a Single Copy of the Integrated Gene

Transgenic Arabidopsis thaliana plants carrying a single copy of integrated DNA can be identified by single-step genomic polymerase chain reaction. The reaction employs two sets of primer pairs with the same melting temperature that amplify the amplicons derived from the integrated T-DNA together with those from an endogenous single-copy gene as a reference. When the band intensity ratio is one, this means that the transgenic plants are carrying a single copy of the integrated gene per haploid.     

转RNAi-SPS5.1拟南芥的获得及表型分析

在克隆了拟南芥蔗糖磷酸合成酶AtSPS5.1的基础上,选择其中特异性的188 bp片段,以正反两个方向插入克隆载体pKANNIBAL中,再将该克隆载体连接入具有NPTⅡ筛选标记的表达载体pART-27中,构建成RNAi-SPS5.1干涉载体.采用农杆菌介导的真空渗透法转化拟南芥,得到T0代的种子,筛选阳性植株,并进行RT-PCR检测,结果表明:RNAi技术能够有效抑制SPS5.1基因的表达,且SPS5.1被干涉后植株的生长发育明显较野生型差,说明该基因的表达对拟南芥生长发育具有重要作用.     

DEAD-box基因家族在拟南芥生长发育中的作用

在RNA代谢过程中,需要许多蛋白和核酸的参与,其中一类蛋白就是RNA解旋酶。RNA解旋酶通过水解ATP获得能量来参与RNA代谢的多个方面,包括核内转录、pre-mRNA的剪切、核糖体发生、核质运输、蛋白质翻译、RNA降解、细胞器内基因的表达。DEAD-box蛋白家族是RNA解旋酶中最大的亚家族,它具有9个保守结构域,因motifyⅡ的保守氨基酸序列Asp-Glu-Ala-Asp(DEAD)而命名。该家族在酵母、拟南芥(Arabidopsis thaliana Heynh.)和人类基因组中都有较多的家庭成员。近年来,研究者对拟南芥DEAD-box蛋白家族的结构和功能进行了一些研究,本文着重总结DEAD-box基因家族对拟南芥生长发育的影响。     

拟南芥AtDAD1超量表达植株对H2O2抗性的研究

构建拟南芥AtDAD1超量表达载体,以农杆菌介导的方法转化拟南芥哥伦比亚生态型,比较AtDAD1超量表达植株和野生型植株表现型的差异,以及两者对H₂O₂抗性的不同。实验显示,AtDAD1转基因拟南芥生长较野生型拟南芥更为强壮,对高浓度H₂O₂有较强的耐受力。测定两者糖含量,发现AtDAD1转基因拟南芥叶片糖的含量明显高于野生型拟南芥叶片。以上结果表明,AtDAD1基因可能参与植物生长发育,并可能在拟南芥抵抗凋亡的过程中发挥重要的作用。     

花粉发育的转录组研究进展

在受精过程中花粉通过其极性生长的花粉管将精细胞运送到胚囊启动双受精，除了在有性生殖过程中的重要作用外，花粉及其极性生长的花粉管也是研究植物生长发育的重要模式材料。随着模式植物拟南芥和水稻基因组测序的完成，在基因组水平上揭示花粉发育以及花粉管极性生长的分子基础已成为可能。经过最近几年的研究已初步明确了花粉转录组特征。本文主要讨论了拟南芥花粉转录组学的研究进展，以期帮助读者对花粉发育的研究有全面了解。     

拟南芥紫色酸性磷酸酶基因(AtPAPs)对磷饥饿的响应

根据拟南芥基因组测序所获得的信息,对拟南芥2号染色 7个可能的紫色酸性磷酸酶基因进行了cDNA克隆、测序及生物信息学分析,并对其在磷饥饿状态下转录水平的表达模式进行了研究,发现大部分的AtPAPs都是组成性表达的,只有AtPAP9,AtPAP10是诱导表达的,其中AtPAP9的转录产物是磷饥饿重新诱导的,而AtPAP10是磷饥饿诱导增加的。     

赤霉素对拟南芥主根分生区和伸长区的调控

赤霉素是一类重要的植物激素,在植物整个生长发育的调控过程中起重要作用。近年来,人们发现赤霉素对拟南芥主根生长存在促进作用。本文从根系的解剖结构、赤霉素的源靶部位、促进作用的机理、赤霉素信号转导途径以及与其他激素的关系等方面,综述了赤霉素对拟南芥主根分生区和伸长区的影响。