Isolation of Pollen Protoplasts in Nicotiana tabacum

A new method for isolation of quantities of mature pollen protoplasts in Nicotiana tabacum has been established. The first step was to germinate mature pollen in Brewbaker and Kwack medium containing 20% sucrose. When most of the pollen grains had just germinated short pollen tubes, they were transferred to an enzymatic solution for the second step. The enzymatic solution contained 1% pectinase, 1% cellulase, 0.5% potassium dextran sulfate, 1 mol/L mannitol, 0.4 mol/L sorbitol in Dx medium with or without 15% Ficoll. The enzymes firstly degraded the pollen tube wall and then the intine. As a result, intact pollen protoplasts were released with the isolation rate up to 50%-70%. Factors affecting pollen protoplast isolation during the germination and maceration of pollen grains were studied. The suceees depended on two key points:pollen germination duration and osmotieum concentration. The optimal germination duration was 30 rain at 30℃. When it was too long, long pollen tubes formed and subsequently, large number of subprotoplasts instead of whole protoplasts were yielded, as the case reported by previous investigators. The optimal concentration of mannitol and sorbitol in enzyme solution was as high as 1.4 mol/L in total. Lowering of the osmoticum concentration resulted in decrease of percentage of pollen protoplasts.     

烟草类锌指基因NtZFL基因的功能分析

从烟草cDNA中分离出一个类锌指基因NtZFL,开放读码框321 bp,编码106个氨基。QRT-PCR分析表明MV、H₂O₂、ABA、冷胁迫处理都提高了NtZFL在烟草的表达,Northern blot分析表明该基因在烟草的不同组织中具有组织特异性,在幼叶和花中表达量较高。亚细胞定位表明NtZFL蛋白是定位在细胞壁中的蛋白。NtZFL基因启动子驱动GUS基因转烟草植株显示在幼苗中整株有表达,但在根部和叶脉处表达量较高。     

New biphenyl derivatives from the leaves of Nicotiana tabacum and their cytotoxic activity

With the aim of searching for new bioactive metabolites from medicinal plants, three new biphenyls, tababiphenyls G–I (1–3), together with four known ones (4–7) were isolated from the leaves of Nicotiana tabacum. Their structures were elucidated by extensive NMR and MS spectroscopic analyses. All the isolated compounds were evaluated for their cytotoxicity against NB4, A549, SHSY5Y, PC3, and MCF7 human cancer cell lines, and some of them showed moderate inhibitory activities against several human tumor cell lines with IC₅₀ values ranging from 2.8 to 9.4 μM.     

Preparation and fusion properties of protoplasts from mature pollen of Nicotiana tabacum

Summary A method to remove the exine from mature tobacco pollen and to release numerous intact pollen protoplasts has been developed. Post-anthesis binucleate pollen was treated with water, buffered with MES at pH 5.5, for two hours. Rupture of the exine was caused by the force of pollen hydration exposing the intine to subsequent enzymatic maceration. The high osmotic pressure (1000 mOsm·kg^-1 H₂O) of pollen protoplasts required a special maceration medium, 4% KCl (w/v). Action of an enzyme solution containing 1% (w/v) Macerozyme and 1% (w/v) Cellulase gave rise to viable protoplasts within 4 hours. When cultured in a tobacco mesophyll protoplast culture medium, the pollen protoplasts underwent regeneration of a cell wall, formation of various tube-shaped structures, and division of the generative nucleus into two nuclei. Using a PEG/Ca²⁺ method pollen protoplasts were fused with diploid mesophyll protoplasts. Evidence of transfer of chloroplasts into the pollen protoplasts was observed after one day of culture.Abbreviations BCP bromocresol purple - FDA fluoresceindiacetate - MES 2-(N-morpholino) ethanesulfonic acid - PEG polyethyleneglycol     

Identification of peptidases in Nicotiana tabacum leaf intercellular fluid

Peptidases in the extracellular space might affect the integrity of recombinant proteins expressed in, and secreted from, plant cells. To identify extracellular peptidases, we recovered the leaf intercellular fluid from Nicotiana tabacum plants by an infiltration-centrifugation method. The activity of various peptidases was detected by an in vitro assay in the presence of specific inhibitors, using BSA and human serum gamma-globulin as substrates. Peptidases were detected by 1- and 2-D zymography in a polyacrylamide gel containing gelatin as substrate. Proteolytic activity was observed over a wide range of molecular masses equal to, or higher than, 45 kDa. To identify the peptidases, the extracellular proteins were digested with trypsin and analyzed by LC and MS. Seventeen peptides showing identity or similarity to predicted plant aspartic, cysteine, and serine peptidases have been identified. The extracellular localization of a cysteine peptidase aleurain homolog was also shown.     

Intrinsic GUS Activity in Various Tissues and During Pollen Development of Nicotiana tabacum

The β-glucuronidase (GUS) gene has been widely used as a reporter gene in the study of plant molecular biology and genetic engineering. One of the major reasons leading to the popularity of GUS-fusion system was the belief that there was no detectable intrinsic GUS activity in plant tissues. However, investigators have been troubled by the "false positive" results or "background" activities when GUS assays were performed. In the present experiment, histochemical observations of intrinsic GUS activity in various tissues and during pollen development of tobacco (Nicotiana tabacurn L. ) was carried out using 5-bromo-4- chloro-3-indolyl-β-D-glucuronic acid (X-gluc) as a substrate for overnight incubation of the treated tissues at 37℃. No detectable intrinsic GUS activity was found in seedling root, stem, leaf, anther wall and stigma of different stages, ovule, as well as isolated generative cell and embryo sac. During pollen development, two peaks of intrinsic GUS activity appeared, one, close to the microspore mitosis and the other from the full maturation of pollen lasting to the post-germination pollen tube stage, no or weak activity was found at other pollen developmental stages. GUS was located in the cytoplasm of the pollen. The pH value of staining solution strongly influenced the experimental results. Blue color was visualized at pH 5, even when 20% methanol or 0.2 mmol/L glucaric acid-l-4-1actone (GAL, a specific GUS inhibitor) were added. At pH 7, no detectable reaction was found at all. The aforementioned results indicate that when using tobacco pollen as the target of GUS gene transformation, the assay should be strictly controlled to neutral condition for avoiding false positive resuits.     

烟草FIE和MSI1基因的克隆及序列分析

采用电子克隆与实验克隆结合的方法获得了烟草胚乳发育相关基因NTFIE和NTMSI1的cDNA序列,序列号分别为EU375458和EU375459.序列分析结果表明,这两个cDNA序列均含有完整的开放读码框,分别编码370和424个氨基酸,含有保守的WD基序.氨基酸序列比对和系统发育分析结果显示,不同物种之间FIE和MSI1基因编码氨基酸序列同源性都较高.组织表达分析结果表明,这两个基因均具有一定程度的组织表达特异性,NTFIE cDNA基因在花中的表达量最多,但在根和茎中未检测到表达,而NTMSI1 cDNA基因只在离体培养的细胞和根中特异性表达.     

Heat stress affects the organization of microtubules and cell division in Nicotiana tabacum cells

To investigate the effects of heat stress on the plant cytoskeleton, the structure of microtubule arrays in N. tabacum suspension cells incubated at 38 or 42°C was analysed. Whilst incubation at 42 °C resulted in the disruption of the majority of cellular microtubules after 30 min, in cells exposed to 38 °C all the microtubule arrays were preserved even after 12 h of incubation, although their organization was altered. The most susceptible were the microtubules of the mitotic spindle and the phragmoplast. Several abnormalities were observed: (i) splitting of the spindle into several parts; (ii) elongation of the spindles; (iii) formation of microtubule asters in mitotic cells, and (iv) elongation of phragmoplast microtubules. Exposure of cells to 38 °C caused a decrease in the mitotic index but an accumulation of telophase cells. The recovery of normal microtubule organization occurred after 12 h. Treatment of the cells subjected to heat stress conditions with an inhibitor of protein synthesis, cycloheximide, did not prevent either the alterations of microtubule organization or accumulation of cells containing phragmoplasts. Therefore, heat shock proteins do not seem to be directly responsible for the microtubule disorganization induced by heat stress.     

重组色氨酸脱羧酶在烟草不同亚细胞区室的表达

将萜烯类吲哚生物碱代谢关键酶———色氨酸脱羧酶 (TDC)的编码基因转到烟草 (NicotianatabacumL .)植物体内 ,标定在不同的亚细胞区室表达。通过蛋白免疫印迹法和色胺在植物体内的累积量测定分析 ,对转基因植物进行筛选。结果表明 ,TDC在叶绿体和胞液中高效表达 ,TDC在叶绿体中的表达水平最高 ,高于在胞液中的表达 ,在内质网和液泡中表达水平很低 ,用蛋白免疫印迹法未检出。     

水杨酸诱导的烟草抗性相关序列的分离

通过已分离鉴定的水杨酸诱导烟草‘云烟85’中与抗性相关的差异表达基因,采用差示筛选和反式Northern检测以及序列分析得到94个烟草差异表达的EST序列。经测序及同源性比较,其中87个有同源序列,7个为新序列;有51个与抗性相关,占总序列的54.3%,其中有系统获得抗性蛋白基因和病程相关蛋白基因等。     

重组色氨酸脱羧酶在烟草不同亚细胞区室的表达

将萜烯类吲哚生物碱代谢关键酶--色氨酸脱羧酶（TDC）的编码基因转到烟草（Nicotiana tabacum L.)植物体内，标定在不同的亚细胞区室表达。通过蛋白免疫印迹法和色胺在植物体内的累积量测定分析，对转基因植物进行筛选。结果表明，TDC在叶绿体和胞液中高效表达，TDC在叶绿体中的表达水平最高，高于在胞液中的表达，在内质网和液泡中表达水平很低，用蛋白免疫印迹法未检出。     

烟草CONSTANS-like基因家族的鉴定与分析

烟草(Nicotiana tabacum)是基因功能分析的模式植物以及重要的经济作物之一,适宜的生存环境对烟草的生长和繁殖至关重要。COL (CONSTANS-like)基因家族编码蛋白不仅调控植物开花,而且在植物生物/非生物胁迫响应中发挥重要作用。该研究通过鉴定烟草COL基因家族成员,分析其基因结构、进化关系、转录调...     

烟草柱头和花柱中阿拉伯半乳糖蛋白的定位

通过Western印迹法、免疫组织化学和超微细胞化学等技术,研究了烟草柱头和花柱中阿拉伯半乳糖蛋白（arabinogalactan-proteins,AGPs）的分布。结果表明烟草柱头和花柱组织中含有大量的AGPs,主要分布于柱头表皮细胞的细胞质和分泌层细胞的胞外基质中,且授粉前后AGPs的分布情况差异不明显;而花柱中的AGPs主要分布于表皮细胞的外层细胞壁、维管组织周围细胞的细胞质及引导组织的胞外基质中;花粉管通过后,引导组织胞外基质中AGPs减少,而花粉管细胞质和花粉管壁中检测到大量AGPs。     

烟草毛状根诱导及其茄尼醇含量初探

茄尼醇是合成泛醌类药物的重要中间体.以发根农杆菌（Agrobacterium rhizogenes）W.T15834感染烟草叶片诱导产生毛状根,探讨其茄尼醇含量变化.结果显示,获得的毛状根能在无外源生长调节剂的MS固体和液体培养基上自主生长,但在液体培养基中培养的毛状根生长更迅速,也不会形成愈伤组织.甘露碱检测及PCR结果证实,发根农杆菌Ri质粒的rolB基因已在烟草（Nicotiana tabacum）毛状根基因组中整合并得到表达.用改进的HPLC法测定烟草毛状根中的茄尼醇含量,其结果为对照根（种子萌发产生的幼苗根）的1.12倍,但仍比废弃烟叶中茄尼醇含量低43.2%.     

Intracellular Localization of a Class IV Chitinase from Yam

Genomic DNA encoding a class IV chitinase was cloned from yam (Dioscorea opposita Thunb) leaves in previous research (Biosci. Biotechnol. Biochem., 68, 1508–1517 (2004)). But this chitinase had an additional sequence composed of eight amino acids (a C-terminal extension) at the C-terminal, compared with class IV chitianses from other plants. In order to clarify the role of this C-terminal extension in cellular localization, plants and suspension-cultured cells of Nicotiana tabacum were transformed with either the cloned yam class IV chitinase gene carrying the C-terminal extension or its truncated gene by the Agrobacterium-mediated method, and then their localization was investigated. The results suggest that the C-terminal extension of yam class IV chitinase plays a role as a targeting signal for plant vacuoles. This is the first report presenting the existence of vacuolar type class IV chitinase.