烟草小孢子母细胞减数分裂过程中微管分布变化

应用间接免疫荧光标记技术和激光共聚焦扫描显微镜成像技术观察了烟草小孢子母细胞减数分裂过程中微管的分布变化。在减数分裂前期,小孢子母细胞中的微管较短,随机分散在细胞质中。在减数分裂中期,细胞质中微管形成纺锤体,控制染色体的分布。进入减数分裂I后期,部分纺锤体微管将两组染色体拉向两级。在减数分裂Ⅱ中期,细胞中的微管又形成两个纺锤体。在减数分裂Ⅱ后期,纺锤体微管解聚为微管蛋白分散在细胞质中。胞质分裂发生在四个细胞核形成之后,通过细胞核之间的质膜向内缢缩分隔四个细胞核,产生四个小孢子。     

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.     

烟草细胞乙醇分解代谢能力的离体调控(英文)

报告了一些重要因子对培养在含有乙醇的培养基上的烟草细胞的乙醇分解代谢能力（ＥＣＡ）的调控效果。在供试的５种生长素和２种细胞分裂素中,ＩＢＡ４ｍｇ／Ｌ和Ｋｔ０．０５ｍｇ／Ｌ最有利于促进ＥＣＡ,而ＮＡＡ２ｍｇ／Ｌ和Ｋｔ０．０２５ｍｇ／Ｌ则最有利于支持处在乙醇胁迫下的细胞的增殖。实验中还发现提高维生素浓度有利于细胞的ＥＣＡ。通过将细胞从低乙醇浓度的培养基转移到较高乙醇浓度的培养基中,能够诱导细胞耐受更高浓度的乙醇并增强细胞的ＥＣＡ。研究结果可以应用于制备适合分离乙醇分解代谢途径中的酶的烟草细胞材料。     

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。     

Illustration of the Genetic Differences in Ozone Sensitivity Between the Varieties Nicotiana tabacum Bel W3 and Bel B Using Various Plant Systems

The ozone-sensitive tobacco variety Bel W₃ was compared with the tolerant cv. Bel B using amphidiploid and amphihaploid genotypes of both. In search of the first genotypical differences, their reaction to acute ozone treatments was investigated with systems of decreasing degree of complexity: whole plants, grown under field, greenhouse and sterile conditions, excised tissues, calli, CCP, MCP and subcellular reactions. It was common to all systems that a fumigation, which clearly exceeds the threshold of the most tolerant material, led to equal reactions in all genotypes in respect of visible injury and membrane leaching. With whole plants and leaf discs growing conditions were found to influence the ozone threshold more than the genotype. Because the most resistant field-grown plants vary widely in their reaction, only sterile or greenhouse grown genotypes were compared. With the exception of whole sterile plants (no genotypical threshold differences), amphihaploids were more susceptible to ozone than their respective amphidiploids as to threshold and sensitivity spectra in all systems investigated. Higher ozone thresholds were detected for Bel B in all systems with one exception: MCP exhibited a lower threshold but also a lower degree of damage in the first buffer range of the sensitivity spectrum than those of Bel W₃. Post-fumigation starch accumulation in mesophyll chloroplasts was the most prominent subcellular ozone reaction.     

Isolation of the male germ unit: organization and function in tobacco (Nicotiana tabacum L.)

Sperm cells are released from pollen tubes of tobacco as linked cells, associated with the vegetative nucleus in an assemblage known as the male germ unit (MGU). Using light microscopy, the MGU assemblage appears to be ensheathed by cytoplasmic material of the pollen tube, which may stabilize their association. Following their release, the shape of the sperm cells and vegetative nucleus changes from an ellipsoidal to a more spheroidal morphology. When most of the cytoplasmic material is dispersed, a boundary remains around the two sperm cells. Using scanning electron microscopy, the cytoplasmic material surrounding the MGU appears filamentous, sometimes twisted and rope-like. Based on these observations, the function of the MGU of tobacco is discussed. Received: 23 February 1998 / Revision received: 21 May 1998 / Accepted: 1 June 1998     

Accumulation of aluminium in the cell wall pectin in cultured tobacco (Nicotiana tabacum L.) cells treated with a combination of aluminium and iron

In nutrient medium, aluminium (Al) accumulation in tobacco cells occurs only in the presence of ferrous ion [Fe(II)]. The localization of Al was examined to elucidate a mechanism of Al accumulation. After the digestion of Al-treated cells with cellulase and pectolyase together, the resulting spheroplasts contained as much Al as the intact cells. However, the cell walls isolated from Al-treated cells also contained as much Al as the intact cells. Comparison of sugar and Al contents in polysaccharide components extracted chemically from cell walls isolated from intact cells and spheroplasts revealed that the enzymes digested most of the cellulose and hemicellulose, but only half of the pectin, and that Al mainly existed in the pectin remaining in the spheroplasts. Gel-permeation chromatography of the pectin fraction (NH₄-oxalate extract) from the cell walls of the intact cells indicated that Al was associated with small polysaccharides of approximately 3–7 kDa. These results suggest that a minor part of pectin is a major site of Al accumulation. The content of cell wall pectin increased during Al treatment in nutrient medium. Taken together, we hypothesize that Al may bind to the pectin newly produced during Al treatment.     

烟草株高变异体的茎尖中内源激素含量变化及其对外源激素的响应

烟草矮秆基因型“农大202’的茎生长过程中茎尖中内源赤霉素（GA3）、生长素（IAA）含量始终低于中、高秆基因型,其内源脱落酸（ABA）和玉米素（ZR）含量则相对较高。喷施外源激素GA,和IAA的结果表明,GA,可调节矮秆基因型茎尖中各内源激素的含量,与正常株高基因型‘K326’的各激素含量相接近,从而促进茎生长,而IAA的作用较小。     

Differential sensitivity of CG and CCG DNA sequences to ethionine-induced hypomethylation of the Nicotiana tabacum genome.

Plant DNA is distinguished from the DNA of all other organisms by its high content of 5-methylcytosine (5mC). 5mC levels may amount to 30% of total cytosines, distributed between the sequences CG and CXG. The results presented here show that the methylation status of CXG sequences could be influenced by culturing tobacco tissues on subtoxic concentrations of ethionine. The hypomethylating effect of ethionine, evaluated as the capability of MspI or HpaII to cleave the DNA, proved to be rather specific for CCG and differed from that or 5-azacytidine which did not discriminate between CG and CXG sequences.     

In vitro double fertilization in Nicotiana tabacum (L.): polygamy compared with selected single pair somatic protoplast and chloroplast fusions

In vitro polygamy was studied mainly by using isolated sperm and central cells of tobacco in order to elucidate the mechanism that might be involved in preventing in vivo polygamy. In 17.5% 4000 M.W. polyethylene glycol, only when two sperm cells were made close enough to each other and adhered to a female cell simultaneously was polygamy possible. If one sperm cell fused with the egg or central cell, within 30 min another sperm cell could not fuse with the same egg or central cell. Similar phenomena were found in selected single somatic cell fusion. When more than two protoplasts adhered to each other simultaneously, fusion was always successful; after two protoplasts fused, within 30 min the fusion products could not fuse with another protoplast under the same conditions. This comparative study revealed this characteristic to be shared by both sexual and somatic cell fusion. However, after cytoplasm reorganization was complete in the fusion product, it was possible for the fusion product to fuse with the third protoplast. This indicates that the obstruction to additional fusion was present only during a certain period after the preceding fusion under certain condition. The possible reason for the effect is discussed. Received: 7 March 2000 / Revision accepted: 15 June 2000     

The fusion of sperm cells and the function of male germ unit (MGU) of tobacco (Nicotiana tabacum L.)

 Sperm cells released from in vivo-in vitro grown pollen tubes of tobacco are associated in pairs and initially enclosed by the plasma membrane of the pollen tube. When the sperm cells are placed together, using glass microinjector needles, in an enzymatic solution, up to half undergo cellular fusion with subsequent nuclear fusion. The frequency of sperm cell fusion decreases with time during the elongation of the pollen tube, suggesting that mechanisms inhibiting self-fusion of sperm cells may develop as the pollen tube elongates through the style toward the ovule. This tendency may play an important role in inhibiting fusion of the two sperm cells inside the calcium-rich synergid where the male germ unit dissociates and sperm cells are transported to their target cells - the egg and central cell. Received: 25 August 1997 / Revision accepted 16 March 1998     

The influence of organic and inorganic chelators on the toxicity of bulk and nanoparticles of zinc oxide during germination and seedling growth of Nicotiana tabacum L.

Nano and bulk-forms of zinc oxide (ZnO) are used extensively in industry and consequently may accumulate in the environment. However, there is little information available on the comparative effects of these forms during the critical early stages of plant life. Furthermore, the role of chelating agents, which affect the bioavailability of metals, in ameliorating plant stress due to exposure to nano and bulk-forms of ZnO is not well characterised. In this study, the effects of different concentrations (0.5, 2.5, 5, 10, 50 and 100 ppm) of nano ZnO (22 nm) and bulk ZnO (natural form, 1000 nm) with and without organic (citrate) and inorganic (EDTA) chelators on germination and seedling growth, and oxidative stress markers of Nicotiana tabacum L. were compared. Chelators (without ZnO) enhanced root growth, whilst ZnO negatively affected seedling growth. ZnO toxicity was often mitigated by adding chelators, especially citrate, although at the highest levels (50 and 100?ppm) of ZnO, toxicity was more pronounced when chelated with EDTA, but was decreased with citrate. Collectively, our findings provide important information regarding the different morpho-physiological and biochemical effects of bulk and nano ZnO and organic and inorganic chelators (citrate and EDTA), which are all prevalent in the environment.     

In vitro induction of stigma-like and style-like structures from receptacle tissue in Nicotiana tabacum L.

Stigma-like and style-like structures were induced from the receptacle tissue in tobacco (Nicotiana tabacum L.). The presence of kinetin was necessary to induce these structures. The structures have a form similar to and the same function as normal stigmas and styles.     

Hybrid genes in the analysis of transformation conditions: II. Transient expression vs stable transformation—analysis of parameters influencing gene expression levels and transformation efficiency

Reports on direct gene transfer have dealt with either the obtention of stable transformants and transgenic plants, or described the use of reporter genes to analyse different aspects of gene expression in plant protoplasts and conditions for their use in transient gene expression assays.
In this paper we present comparisons between several transformation techniques, show species-specific differences in efficiencies of stable transformants and in the levels of transient gene expression, and report on the identification of major parameters responsible for DNA uptake as judged from transient chloramphenicol acetyl transferase (CAT) expression levels and from efficiencies of transformation based on kanamycin-resistance. The described procedures have been simplified, optimized and standardized and should allow routine use with a great variety of plant species.     

Somatic embryogenesis in Nicotiana tabacum L.: induction by thidiazuron of direct embryo differentiation from cultured leaf discs

Summary Induction of somatic embryogenesis by different growth regulators was examined in leaf disc cultures of Nicotiana tabacum L. Direct differentiation of somatic embryos occurred on media supplemented with naphthaleneacetic acid (NAA) and N⁶-benzylaminopurine (BAP). Thidiazuron (N-phenyl-N-1, 2,3,-thiadiazol-5-ylurea; TDZ) not only substituted for the most effective NAA-BAP combination but also induced a higher frequency of somatic embryogenesis. Regenerated somatic embryos were capable of developing into plants.Abbreviations BAP N⁶-benzylaminopurine - MS Murashige and Skoog (1962) medium - NAA Naphthaleneacetic acid - TDZ N-phenyl-N-1,2,3,- thiadiazol-5-ylurea     

Response of shape in vitro cultures of shape Nicotiana tabacum L. to copper stress and selection of plants from Cu-tolerant callus

In Nicotiana tabacum L. var. BEL W3 copper (Cu) at concentrations higher than 50 μM significantly inhibited callus growth and shoot regeneration. After 5–6 months of culture only a few morphogenic callus lines survived in the presence of 100 μM Cu. These calluses showed the capacity to grow and regenerate shoots through successive subcultures on medium containing 100 μM Cu. The 100 μM Cu-tolerant shoots, in comparison to regenerated control shoots, formed roots only when cultured in the presence of 100 μM Cu. From five independent Cu-tolerant callus lines in a culture period of 4–5 months more than 50 plants (defined ‘tolerant’) able to grow in presence of 100 μM Cu were obtained. These plants showed normal xylem tissue formation while control regenerated plants growing in normal Cu MS content (0.1 μM) had few xylem elements in the central cylinder. No difference as far chlorophyll content and chloroplast structure was found among Cu-tolerant and control plants. In Cu-tolerant plants, dry matter production was higher than in controls, particularly in roots. This revised version was published online in June 2006 with corrections to the Cover Date.     

Further studies on the effects of different auxins and cytokinins on flower formation in thin cell layers of Nicotiana tabacum: The effects of zeatin riboside, dihydrozeatin and dihydrozeatin riboside

Organogenesis in thin cell layers of Nicotiana tabacum L. was studied in relation to the effects of natural and synthetic auxins in combination with various cytokinins. All cytokinins tested, benzyladenine (BA), kinetin, zeatin (Z), zeatin riboside (ZR), N⁶-Δ²-isopentenyl) adenine (IPA), dihydrozeatin [(diH)Z] and dihydrozeatin riboside [(diH)ZR], seem to be active in flower bud formation. In addition to the initiation of flower buds, vegetative buds or roots were also formed on the explants in the presence of BA, Z or IPA as exogenous cytokinins. Only dihydrozeatin and its riboside stimulated the initation of flower buds alone (as is known for kinetin), especially if supplemented with indole-3-acetic acid (IAA) as exogenous auxin. A high number of explants with flower buds was also found with high cytokinin/2,4-D ratios. In these conditions the presence of (diH)Z yielded the higest number of flower buds per explant.