Tissue culture propagation alters plant-microbe interactions in tobacco rhizosphere

We have compared properties of roots from different lines (genotypes) of tobacco raised either in tissue culture or grown from seed. The different lines included unmodified plants and plants modified to express reduced activity of the enzyme cinnamoyl-CoA reductase, which has a pivotal role in lignin biosynthesis. The size and structure of the rhizosphere microbial community, characterized by adenosine triphosphate and phospholipid fatty acid analyses, were related to root chemistry (specifically the soluble carbohydrate concentration) and decomposition rate of the roots. The root material from unmodified plants decomposed faster following tissue culture compared with seed culture, and the faster decomposing material had significantly higher soluble carbohydrate concentrations. These observations are linked to the larger microbial biomass and greater diversity of the rhizosphere communities of tissue culture propagated plants.

Promoting sustainability: Efficacy and adoption of tobacco-based insecticides in Nigeria

The promotion of technologies seen to be aiding in the attainment of agricultural sustainability has been Popular amongst Northern-based development donors for many years. One of these, botanical insecticides (e.g., those based on neem, Pyrethrum and tobacco) have been a particular favorite as they are equated with being 'natural' and hence less damaging to human health and the environment. This paper describes the outcome of interactions between one non-government organisation (NGO), the Diocesan Development Services (DDS), based in Kogi State, Nigeria, and a major development donor based in Europe that led to the establishment of a programme designed to promote the Virtues of a tobacco-based insecticide to small-scale farmers. The Tobacco Insecticide Programme (TIP) began in the late 1980s and ended in 200 1, absorbing significant quantities of resource in the process. TIP began with exploratory investigations of efficacy on the DDS seed multiplication farm followed by stages of researcher-managed and farmer-managed on-farm trials. A survey in 2002 assessed adoption of the technology by farmers. While yield benefits from using the insecticide were nearly always positive and statistically significant relative to an untreated control, they were not as good as commercial insecticides. However, adoption of the tobacco insecticide by local farmers was poor. The paper discusses the reasons for poor adoption, including relative benefits in gross margin, and uses the TIP example to explore the differing power relationships that exist between donors, their field partners and farmers. (C) 2004 by The Haworth Press, Inc. All rights reserved.

Tissue culture propagation alters plant-microbe interactions in tobacco rhizosphere

We have compared properties of roots from different lines (genotypes) of tobacco raised either in tissue culture or grown from seed. The different lines included unmodified plants and plants modified to express reduced activity of the enzyme cinnamoyl-CoA reductase, which has a pivotal role in lignin biosynthesis. The size and structure of the rhizosphere microbial community, characterized by adenosine triphosphate and phospholipid fatty acid analyses, were related to root chemistry (specifically the soluble carbohydrate concentration) and decomposition rate of the roots. The root material from unmodified plants decomposed faster following tissue culture compared with seed culture, and the faster decomposing material had significantly higher soluble carbohydrate concentrations. These observations are linked to the larger microbial biomass and greater diversity of the rhizosphere communities of tissue culture propagated plants.

Selenium persistency and speciation in the tissues of lambs following the withdrawal of dietary high-dose selenium-enriched yeast

The objective was to determine the concentration of total selenium (Se) and the proportion of total Se comprised as selenomethionine (SeMet) and selenocysteine (SeCys) in post mortem tissues of lambs in the six weeks period following the withdrawal of a diet containing high dose selenized yeast (SY), derived from a specific strain of Saccharomyces cerevisae CNCM (Collection Nationale de Culture de Micro-organism) I-3060. Thirty Texel x Suffolk lambs used in this study had previously received diets (91 days) containing either high dose SY (HSY; 6.30 mg Se/kg DM) or an unsupplemented control (C; 0.13 mg Se/kg DM). Following the period of supplementation all lambs were then offered a complete pelleted diet, without additional Se (0.15 mg Se/kg DM), for 42 days. At enrollment and 21 and 42 days later, five lambs from each treatment were blood sampled, euthanased and samples of heart, liver, kidney and skeletal muscle (Longissimus Dorsi and Psoas Major) tissue were retained. Total Se concentration in whole blood and tissues was significantly (P < 0.001) higher in HSY lambs at all time points that had previously received long term exposure to high dietary concentrations of SY. The distribution of total Se and the proportions of total Se comprised as SeMet and SeCys differed between tissues, treatment and time points. Total Se was greatest in HSY liver and kidney (22.64 and 18.96 mg Se/kg DM, respectively) and SeCys comprised the greatest proportion of total Se. Conversely, cardiac and skeletal muscle (Longissimus Dorsi and Psoas Major) tissues had lower total Se concentration (10.80, 7.02 and 7.82 mg Se/kg DM, respectively) and SeMet was the predominant selenized amino acid. Rates of Se clearance in HSY liver (307 µg Se/day) and kidney (238 µg Se/day) were higher compared with HSY cardiac tissue (120 µg Se/day) and skeletal muscle (20 µg Se/day). In conclusion differences in Se clearance rates were different between tissue types, reflecting the relative metabolic activity of each tissue, and appear to be dependant upon the proportions of total Se comprised as either SeMet or SeCys.

Time patterns in UK demand for alcohol and tobacco: an application of the EM algorithm

Capturing the pattern of structural change is a relevant task in applied demand analysis, as consumer preferences may vary significantly over time. Filtering and smoothing techniques have recently played an increasingly relevant role. A dynamic Almost Ideal Demand System with random walk parameters is estimated in order to detect modifications in consumer habits and preferences, as well as changes in the behavioural response to prices and income. Systemwise estimation, consistent with the underlying constraints from economic theory, is achieved through the EM algorithm. The proposed model is applied to UK aggregate consumption of alcohol and tobacco, using quarterly data from 1963 to 2003. Increased alcohol consumption is explained by a preference shift, addictive behaviour and a lower price elasticity. The dynamic and time-varying specification is consistent with the theoretical requirements imposed at each sample point. (c) 2005 Elsevier B.V. All rights reserved.

The cell wall and secretory proteome of a tobacco cell line synthesising secondary wall

The utility of plant secondary cell wall biomass for industrial and biofuel purposes depends upon improving cellulose amount, availability and extractability. The possibility of engineering such biomass requires much more knowledge of the genes and proteins involved in the synthesis, modification and assembly of cellulose, lignin and xylans. Proteomic data are essential to aid gene annotation and understanding of polymer biosynthesis. Comparative proteomes were determined for secondary walls of stem xylem and transgenic xylogenic cells of tobacco and detected peroxidase, cellulase, chitinase, pectinesterase and a number of defence/cell death related proteins, but not marker proteins of primary walls such as xyloglucan endotransglycosidase and expansins. Only the corresponding detergent soluble proteome of secretory microsomes from the xylogenic cultured cells, subjected to ion-exchange chromatography, could be determined accurately since, xylem-specific membrane yields were of poor quality from stem tissue. Among the 109 proteins analysed, many of the protein markers of the ER such as BiP, HSP70, calreticulin and calnexin were identified, together with some of the biosynthetic enzymes and associated polypeptides involved in polymer synthesis. However 53% of these endomembrane proteins failed identification despite the use of two different MS methods, leaving considerable possibilities for future identification of novel proteins involved in secondary wall polymer synthesis once full genomic data are available.

Modification of hemicellulose content by antisense down-regulation of UDP-glucuronate decarboxylase in tobacco and its consequences for cellulose extractability

Extractability and recovery of cellulose from cell walls influences many industrial processes and also the utilisation of biomass for energy purposes. The utility of genetic manipulation of lignin has proven potential for optimising such processes and is also advantageous for the environment. Hemicelluloses, particularly secondary wall xylans, also influence the extractability of cellulose. UDP-glucuronate decarboxylase produces UDP-xylose, the precursor for xylans and the effect of its down-regulation on cell wall structure and cellulose extractability in transgenic tobacco has been investigated. Since there are a number of potential UDP-glucuronate decarboxylase genes, a 490 bp sequence of high similarity between members of the family, was chosen for general alteration of the expression of the gene family. Sense and antisense transgenic lines were analysed for enzyme activity using a modified and optimised electrophoretic assay, for enzyme levels by western blotting and for secondary cell wall composition. Some of the down-regulated antisense plants showed high glucose to xylose ratios in xylem walls due to less xylose-containing polymers, while arabinose and uronic acid contents, which could also have been affected by any change in UDP-xylose provision, were unchanged. The overall morphology and stem lignin content of the modified lines remained little changed compared with wild-type. However, there were some changes in vascular organisation and reduction of xylans in the secondary walls was confirmed by immunocytochemistry. Pulping analysis showed a decreased pulp yield and a higher Kappa number in some lines compared with controls, indicating that they were less delignified, although the level of residual alkali was reduced. Such traits probably indicate that lignin was less available for removal in a reduced background of xylans. However, the viscosity was higher in most antisense lines, meaning that the cellulose was less broken-down during the pulping process. This is one of the first studies of a directed manipulation of hemicellulose content on cellulose extractability and shows both positive and negative outcomes.

Modification of hemicellulose content by antisense down-regulation of UDP-glucuronate decarboxylase in tobacco and its conscequence for cellulose extractability

Extractability and recovery of cellulose from cell walls influences many industrial processes and also the utilisation of biomass for energy purposes. The utility of genetic manipulation of lignin has proven potential for optimising such processes and is also advantageous for the environment. Hemicelluloses, particularly secondary wall xylans, also influence the extractability of cellulose. UDP-glucuronate decarboxylase produces UDP-xylose, the precursor for xylans and the effect of its down-regulation on cell wall structure and cellulose extractability in transgenic tobacco has been investigated. Since there are a number of potential UDP-glucuronate decarboxylase genes, a 490 bp sequence of high similarity between members of the family, was chosen for general alteration of the expression of the gene family. Sense and antisense transgenic lines were analysed for enzyme activity using a modified and optimised electrophoretic assay, for enzyme levels by western blotting and for secondary cell wall composition. Some of the down-regulated antisense plants showed high glucose to xylose ratios in xylem walls due to less xylose-containing polymers, while arabinose and uronic acid contents, which could also have been affected by any change in UDP-xylose provision, were unchanged. The overall morphology and stem lignin content of the modified lines remained little changed compared with wild-type. However, there were some changes in vascular organisation and reduction of xylans in the secondary walls was confirmed by immunocytochemistry. Pulping analysis showed a decreased pulp yield and a higher Kappa number in some lines compared with controls, indicating that they were less delignified, although the level of residual alkali was reduced. Such traits probably indicate that lignin was less available for removal in a reduced background of xylans. However, the viscosity was higher in most antisense lines, meaning that the cellulose was less broken-down during the pulping process. This is one of the first studies of a directed manipulation of hemicellulose content on cellulose extractability and shows both positive and negative outcomes.