The Mechanical Properties of Xylem Tissue from Tobacco Plants (Nicotiana tabacum'Samsun')

Tobacco plants (Nicotiana tabacum‘Samsun’) havebeen grown with an antisense CAD (cinnamyl alcohol dehydrogenase)gene. This modifies lignin production, resulting in lignin witha greater aldehyde content which is easier to extract chemically.This lignin probably has a reduced crosslink density. The changedproperties of the lignin affect the longitudinal tensile modulusof the xylem tissue (wood), reducing it by one third, from 2.8GPa to 1.9 GPa. Tobacco xylem tissue cell walls are more sensitiveto changes in the properties of the matrix than can be predictedusing current cell wall mechanical models.Copyright 1998 Annalsof Botany Company Tobacco,Nicotiana tabacum, xylem tissue, Young's modulus, matrix polymer connectivity, plant biomechanics.     

Modelling the Mechanical Properties of Xylem Tissue from Tobacco Plants (Nicotiana tabacum'Samsun') by Considering the Importance of Molecular and Micromechanisms

Tobacco plants (Nicotiana tabacum‘Samsun’) havexylem cell walls which are more sensitive to changes in theproperties of the matrix than was predicted using current cellwall mechanical models. A model is proposed which can accountfor the importance of the cell wall matrix in determining themodulus of the material. This model is based on a helical springsystem, with micromechanisms operating at the molecular scale.Xylem tissue fibre cells can behave as helical springs whenthe crosslink density of lignin is low, or they can behave likea composite sheet with fibres at an angle to the applied loadwhen the crosslink density is high. This highlights the importanceof molecular modelling when the properties of complex biologicalmaterials are being investigated.Copyright 1998 Annals of BotanyCompany Tobacco,Nicotiana tabacum, xylem tissue, Young's modulus, matrix polymer connectivity, plant biomechanics.     

转基因植物快速检测方法的研究

本试验对转基因植物检测中的DNA提取和PCR扩增程序作了改进。经试验,本研究建立的DNA快速提取法与目前广泛使用的CTAB法相比更为简便,快速和经济,提取的DNA质量主扩增效果无明显差异,可用于多种转基因植物,多种植物组织的DNA提取,利用复合PCR法可在同一反应管中同步检测35N,NOS及CP4－EPSPS基因,明显提高了检测效率。应用本试验建立的DNA快速提取－复合PCR扩增－银染检测技术可在6小时内得出结果,达到了快速,简便,灵敏,可靠的检测目的。     

Transgenic Tobacco (Nicotiana tabacum SR1) Plants Expressing the Gene Coding for Serratia marcescens Nuclease

The gene coding for the secreted Serratia marcescens endonuclease was fused with the mannopine synthase promoter of Agrobacterium tumefaciens Ti plasmid and transferred to Nicotiana tabacum SR1 plants. The promoter is leaf- and root-specific. The resulting transgenic plants demonstrated elevated nuclease activity. The level of the transgene product was determined in the transgenic lines.     

Carbohydrate-limited Growth Kinetics of Tobacco (Nicotiana rustica L.) Callus

Logistic curves were fitted to sigmoidal growth data obtained from tobacco (Nicotiana rustica L.) callus grown on media prepared with 0.1, 0.03, 0.01, and 0.003 m sucrose. Analysis of the growth curves indicated that final yields and specific growth rates were influenced by the initial sucrose concentration. Growth yields from the four treatments were similar (0.61 +/- 0.04 gram dry tissue per gram sucrose supplied). Initial specific growth rates exhibited a Michaelis-Menten dependency on initial sucrose concentration such that the V(max) = 0.18 g g(-1) day(-1) and Km = 0.0037 m sucrose.     

Using Viscoelastic Properties of the Woody Tissue from Tobacco Plants (Nicotiana tabacum) to Comment on the Molecular Structure of Cell Walls

Lignin in the cell walls of woody tissue has a much lower crosslinkdensity in tobacco wood than in tree wood. This causes tobaccowood to show very different viscoelastic behaviour. With theaid of genetically modified plants, it is shown that the ligninin tobacco plant cell walls behaves in much the same way asa polymer solution. It exhibits both rate stiffening and ratethinning behaviour due to the entangled nature of the ligninnetworks. The hydrophobic portions of lignin have a very lowpolymer chain crosslink density, hence entanglements make asignificant contribution.Copyright 1998 Annals of Botany Company Tobacco plants, lignin, polymer solution, shear thinning, stress relaxation.     

Ethylene Production by Tobacco (Nicotiana tabacum) Callus

Tobacco callus cultures grown on defined agar-solidified media produced ethylene in differing amounts, which were related to cultural treatment and age of the callus. There was a close correlation between the rate of ethylene production and growth. In darkness, maximal rates occurred in the third week of growth with ethylene production in the range of 750 nl (callus piece)^?1 d^?1 (fr. wt. = 1.5 g), and in the light, maximal rates occurred in the first week of growth, 200 nl (callus piece)^?1 d^?1 (fr. wt. = 200 mg). Growth was also correlated with ethylene production when the latter was altered by exposure of the callus to inhibitors of ethylene synthesis, L-canaline, benzyl isothiocyanate, and 3,5-diiodo-4-hydroxy-benzoic acid. No correlation was found following treatment with AgNO₃, a presumptive inhibitor of ethylene action. The inhibition of growth and ethylene production by L-canaline was partially reversed by gassing the cultures with ethylene (1 μl/1). A mercuric perchlorate sink had no significant effect on growth. A possible relationship between ethylene evolution and growth is discussed.     

Effects of Iron Excess on Nicotiana plumbaginifolia Plants (Implications to Oxidative Stress)

Fe excess is believed to generate oxidative stress. To contribute to the understanding of Fe metabolism, Fe excess was induced in Nicotiana plumbaginifolia grown in hydroponic culture upon root cutting. Toxicity symptoms leading to brown spots covering the leaf surface became visible after 6 h. Photosynthesis was greatly affected within 12 h; the photosynthetic rate was decreased by 40%. Inhibition of photosynthesis was accompanied by photoinhibition, increased reduction of photosystem II, and higher thylakoid energization. Fe excess seemed to stimulate photorespiration because catalase activity doubled. To cope with cellular damage, respiration rate increased and cytosolic glucose-6-phosphate dehydrogenase activity more than doubled. Simultaneously, the content of free hexoses was reduced. Indicative of generation of oxidative stress was doubling of ascorbate peroxidase activity within 12 h. Contents of the antioxidants ascorbate and glutathione were reduced by 30%, resulting in equivalent increases of dehydroascorbate and oxidized glutathione. Taken together, moderate changes in leaf Fe content have a dramatic effect on plant metabolism. This indicates that cellular Fe concentrations must be finely regulated to avoid cellular damage most probably because of oxidative stress induced by Fe.     

Reduction of Cadmium Availability to Tobacco (Nicotiana tabacum) Plants using Soil Amendments in Low Cadmium-contaminated Agricultural Soils: A Pot Experiment

Cadmium (Cd) concentration in field-grown tobacco leaves usually ranges from < 0.5 to 5 mg Cd kg^–1 dry matter (DM). Reducing bioavailability of soil Cd by adding amendments to the soil could be suitable to mitigate Cd uptake by tobacco plants. However, little is known on the effect of inorganic amendments on agricultural soils with low Cd concentrations. Therefore, we performed a pot experiment with tobacco plants that were grown during 56 days in two neutral to alkaline agricultural soils with low total Cd concentrations (soil 1 = 0.4, soil 2 = 0.7 mg kg^–1). Both soils were amended or not with 1 or 5% of sepiolite, zeolite, hydroxyapatite and apatite II™. Major and trace elements were measured in mid-stalk position leaves. Soil metals were measured in a DTPA soil extraction to assess the effect of the amendments on metal bioavailability. Some amendments significantly reduced Cd concentration in tobacco leaves, but the effect differed between the two soils tested. In soil 1, the use of zeolite at the 1% dose was the most efficient, reducing the average Cd concentration from 0.6 to 0.4 mg kg^–1. In soil 2, the 5% hydroxyapatite treatment led to the maximal reduction in Cd concentration (50%), with an average final Cd concentration in leaves of 0.7 mg kg^–1 (control: 1.5 mg kg^–1). There was a dose effect for some amendments in soil 2 (containing more Cd), suggesting a reduced efficiency of the amendment at the lowest addition rate. DTPA extractable Cd and Zn measured at the end of the pot experiment were correlated to the metal concentrations in tobacco leaves suggesting that (1) the reduction in leaf Cd concentration was due to a reduction in metal availability to tobacco and (2) DTPA may be a suitable extractant to estimate Cd availability to tobacco plants in these two soils. In addition, a batch experiment was performed with the same soils to test a larger number of amendments, including the four tested in the pot experiment. Results were compared to those of the pot experiment to assess whether a batch experiment may predict the efficiency of an amendment on a given soil. It gave results compatible with those from the pot experiment except for the sepiolite and highlighted the broad range of potential amendments available for heavy metal remediation in crop plants.     

Mechanical Wounding Caused by Inoculation Influences the Photosynthetic Response of Nicotiana benthamiana Plants to Plum Pox Potyvirus

Plants of Nicotiana benthamiana (Gray) (60 d old) were mechanically inoculated by a spreading of the fourth and fifth leaves with inoculum with or without plum pox potyvirus (PPV). Changes in growth parameters and selected photosynthetic characteristics were followed in control and inoculated plants in the locally affected leaves (LA) during 11 d after inoculation (DAI), in systemically affected leaves immature at time of inoculation (SAI) during 14–25 DAI, and in systemically affected leaves developed after the inoculation (SAD) during 28–39 DAI. The pure mechanical damage caused by inoculation induced a decrease in the net photosynthetic rate (P _N) in LA and SAD leaves, and an increase in the steady-state value of the non-photochemical chlorophyll (Chl) fluorescence quenching q_N. The q_N increase appeared in certain time intervals in all measured leaves on plants, so it could be regarded as indication of a systemic reaction of plant to the local mechanical injury. The viral infection developed in LA leaves and spread to SAI and SAD leaves was documented by the ELISA-DASI method. The plant height and area of SAI and SAD leaves were lower in infected plants. The combined effect of mechanical damage and viral infection caused a decrease in P _N only in LA and SAD leaves. In SAD leaves, an increased relative height of the J step (V_J) in the O-J-I-P Chl fluorescence transient together with a lower B/A band ratio of thermoluminescence glow curves reflected a damage to the acceptor side of photosystem 2 (PS2) caused by the viral infection, and a faster kinetics of the induction of the photochemical quenching coefficient q_P of Chl fluorescence indicated a faster Q_A ^– re-oxidation in the remaining undamaged centres of PS2.     

烟草的历史

1　吸烟习俗的起源和传播当今遍布于全世界各地的烟草原产于美洲 ,最早栽培并吸食的是当地印第安人。美洲印第安人从什么时候开始吸烟 ,迄今还不很清楚。目前已发现最早的资料是在墨西哥恰帕斯州的帕伦克 ,有在公元 4 32年修建的玛雅文化的古典神庙中的一块浮雕 ,可以看到古代玛雅人在宗教的仪式中有人用管状烟斗来吸烟 ,而且还在喷出烟雾。在美国阿利桑那州的帕布罗城发现公元 6 5 0年前后印第安人居住的洞穴遗址 ,其中有烟叶实物和烟斗 ,烟斗中还存有烟灰。在墨西哥马德雷山上海拔 12 0 0ｍ处的一个山洞中 ,发现一个塞有烟草的空心草管 ,…     

Effects of Ambient CO2 Concentration on Growth and Nitrogen Use in Tobacco (Nicotiana tabacum) Plants Transformed with an Antisense Gene to the Small Subunit of Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase

Growth of the R1 progeny of a tobacco plant (Nicotiana tabacum) transformed with an antisense gene to the small subunit of ribulose-1,5-carboxylase/oxygenase (Rubisco) was analyzed under 330 and 930 [mu]bar of CO2, at an irradiance of 1000 [mu]mol quanta m-2 s-1. Rubisco activity was reduced to 30 to 50% and 13 to 18% of that in the wild type when one and two copies of the antisense gene, respectively, were present in the genome, whereas null plants and wild-type plants had similar phenotypes. At 330 [mu]bar of CO2 all antisense plants were smaller than the wild type. There was no indication that Rubisco is present in excess in the wild type with respect to growth under high light. Raising ambient CO2 pressure to 930 [mu]bar caused plants with one copy of the DNA transferred from plasmid to plant genome to achieve the same size as the wild type at 330 [mu]bar, but plants with two copies remained smaller. Differences in final size were due mostly to early differences in relative rate of leaf area expansion (m2 m-2 d-1) or of biomass accumulation (g g-1 d-1): within less than 2 weeks after germination relative growth rates reached a steady-state value similar for all plants. Plants with greater carboxylation rates were characterized by a higher ratio of leaf carbon to leaf area, and at later stages, they were characterized also by a relatively greater allocation of structural and nonstructural carbon to roots versus leaves. However, these changes per se did not appear to be causing the long-term insensitivity of relative growth rates to variations in carboxylation rate. Nor was this insensitivity due to feedback inhibition of photosynthesis in leaves grown at high partial pressure of CO2 in the air (pa) or with high Rubisco activity, even when the amount of starch approached 40% of leaf dry weight. We propose that other intrinsic rate-limiting processes that are independent of carbohydrate supply were involved. Under plentiful nitrogen supply, reduction in the amount of nitrogen invested in Rubisco was more than compensated for by an increase in leaf nitrate. Nitrogen content of organic matter, excluding Rubisco, was unaffected by the antisense gene. In contrast, it was systematically lower at elevated pa than at normal pa. Combined with the positive effects of pa on growth, this resulted in the single-dose antisense plants growing as fast at 930 [mu]bar of CO2 as the wild-type plants at 330 [mu]bar of CO2 but at a lower organic nitrogen cost.     

遗传修饰工程体的生态安全性

遗传修饰工程体的生态安全性引起了人们的广泛关注。本文对转基因植物外源基因逃逸、对非靶标生物的影响、抗生素抗性基因的安全性以及生防工程菌的生态安全性等问题作了讨论。     

烤烟SSR标记多样性及与致香物质的关联分析

了解烤烟品种的遗传多样性,寻找与烤烟致香物质含量关联的分子标记,挖掘高致香物质含量的优异等位变异与种质,对香气品质分子标记辅助育种具有重要意义。本研究检测了山东和四川2个生态区60份烤烟种质中76种致香物质的含量;筛选覆盖全基因组的1914个SSR标记,利用得到的390对多态性引物扩增供试群体。用基于Nei's(1983)遗传距离的邻接法(Neighor-joining,NJ)进行聚类分析。在分析群体结构的基础上,利用混合线性模型进行关联分析,并进一步发掘极显著关联标记的优异等位变异和种质。结果检测到928个等位变异,平均每个位点2.38个等位变异,变化范围为2~5个。PIC值的变化范围分别为0.141~0.733,平均值0.332。这说明供试群体遗传多样性较丰富。聚类分析将该群体划分为2个亚群,划分结果体现了烤烟品种间的亲缘关系;群体结构分析与聚类结果基本一致。关联分析结果显示:共有56个SSR标记位点与41种致香物质同时在2个生态区显著关联(P0.05)。共5个标记与6个性状在2个生态区极显著关联(P0.01),6种致香物质为草酸、肉豆蔻酸、2,4-庚二烯醛、芳樟醇、a-松油醇和gamma-壬内酯,关联标记分别为PT50662、PT60191、PT52263、PT60597、PT60597和PT52722。关联位点表型解释率为12.54%~42.20%。进一步分析发掘了14种致香物质的优异等位变异,并筛选出含增效等位变异较多的种质:净叶黄、抗9201、单育二号、满屋香、金星6007、秦烟95等。这对香气品质分子标记辅助选择育种以及亲本材料选配等奠定了基础。     

烟草ESTs资源的SSR信息分析

烟草ESTs数量迅速增加为开发新的SSR标记提供了宝贵的资源.经过软件分析,对242 683条烟草ESTs序列剔除冗余序列,在211 728条非冗余烟草ESTs序列中,共检索出9 339个SSR,SSR之间的距离约为14.21 kb,检出率为4.41%,包括216种重复基元.其中三核苷酸重复类型的SSR占主导地位,占总SSR的50.34%,其次为二核苷酸和单核苷酸,分别为23.00%,16.48%,其余重复类型所占比例均不足5%.在所有重复基元中,A/T重复为主要类型,占所有重复14.68%,其次为AT/TA、AG/TC、AAG/TTC,分别为10.49%、9.48%、6.85%.随机设计10对EST-SSR引物,对6个品种烟草进行扩增,10对EST-SSR引物均能扩增出产物,其中1对引物在6个品种有多态性.本研究为烟草EST-SSR标记的建立和进一步应用奠定了基础.