Using planar lipid-bilayers to study plant ion channels

Ion channels are found in most plant membranes. They catalyse the rapid passive uniport of particular ions with varying selectivity. Planar lipid-bilayer (PLB) techniques have been developed to study the electrical activities of single ion channels in well-defined lipid and aqueous environments. They greatly facilitate both the biophysical and biochemical characterisation of ion channels and complement both conventional impaling electrode and membrane-patch voltage-clamping (patch-clamping) electrophysiological techniques applied in vivo. Bilayers can be formed across the end of patch-clamp pipettes or across apertures in specifically designed chambers. Ion channels in native membranes and purified, genetically altered or synthetic ion channels, proteins and peptides can all be studied in PLBs. The main applications of PLBs are (1) to study ion channels in membranes inaccessible to patch-clamp electrodes, (2) to provide a functional assay system during channel-protein purification and (3) to investigate the relationship between the molecular structure of ion channels and their conductance properties. In the present article we describe the techniques available for reconstitution and analysis of ion channels in PLBs and discuss how the PLB technique has been, and may be, useful to the study of plant ion channels.     

Impaired stem-growth responses to blue-light irradiance in light-grown transgenic tobacco seedlings overexpressing Avena phytochrome A

The effects of blue light (B) on stem extension-growth were compared in light-grown seedlings, of tobacco overexpressing Avena phytochrome A and its isogenic wild type (WT). Under natural radiation, lowering the levels of B reaching the whole shoot promoted stem extension growth in WT but not in transgenic seedlings. Under controlled conditions, the seedlings were exposed to white light (WL) or WL minus B, each one provided at two different irradiances. In WT seedlings stem extension growth was promoted by lowering B at both irradiance levels. In transgenic seedlings a reduction of B was promotive only at low irradiance levels. The seedlings were also grown under WL, WL minus B, WL minus red light (R) and far-red light (FR) or WL minus R, FR and B. In the WT, lowering B promoted stem extension growth irrespective of R+FR levels. In the transgenics, B was effective only at very low levels of R+FR (i.e. at low phytochrome cycling rates). Lowering the Pfr levels at the end of the day promoted extension growth in wild type and transgenic seedlings. Responses to B were not observed in transgenic seedlings having low Pfr levels at the end of the day. The results suggest that the overexpressed phytochrome A acts mainly via irradiance-dependent reactions. When these reactions are highly expressed, B responses are not observed.     

Literature on archaeological remains of cultivated plants (1991/1992)

A total of 422 publications from 1991 and 1992 on archaeological remains of cultivated plants have been collected. A list is given of the finds according to species, country and age.     

Reduced lignin in transgenic plants containing a caffeic acidO-methyltransferase antisense gene

Lignin is a major structural polymer of secondarily thickended plant vascular tissue and fibres, imparting mechanical strength to stems and trunks and hydrophobicity to conducting vessels. Constitutive expression of a lucerne caffeic acid 3-O-methyltransferase antisense RNA in transgenic tobacco leads to a significant reduction in lignin content, particularly in the younger parts of the stems, without apparent alterations in lignin monomer composition. These observations open up the possibility of genetically manipulating plants with reduced lignin for improved processing and biomass digestibility.     

Opportunities for gene transfer from transgenic oilseed rape (Brassica napus) to related species

Before novel transgenic plant genotypes are grown outside containment facilities and evaluated under field conditions, it is necessary to complete a risk assessment to consider the possible consequences of that release. An important aspect of risk assessment is to consider the likelihood and consequences of the transgene being transferred by cross-pollination to related species, including other crops, weeds and ruderal populations. The purpose of this report is to review the literature to assess the ease with whichBrassica napus can hybridize with related species. The evidence for hybridization is considered at three levels: a) by open pollination, b) by hand pollination and c) by the use ofin vitro ovule and embryo rescue techniques; and also examines the fertility and vigour of the F₁, F₂ and backcross generations. Four species are reported to hybridize withB. napus by open pollination:B. rapa andB. juncea using fully fertile parents; andB. adpressa andR. raphanistrum using a male-sterileB. napus parent. Seventeen species are reported to form hybrids (including the four species above) withB. napus when pollination is carried out manually. At least 12 of these species were unable to form F₂ progeny, and eight were unable to produce progeny when the F₁ was backcrossed to one of the parental species. Many factors will influence the success of hybridization under field conditions, including: distance between the parents, synchrony of flowering, method of pollen spread, specific parental genotypes used, direction of the cross and the environmental conditions. Even where there is a possibility of hybridization betweenB. napus and a related species growing in the vicinity of a release, poor vigour and high sterility in the hybrids will generally mean that hybrids and their progeny will not survive in either an agricultural or natural habitat.     

海河流域植物硫素含量特征的研究

本文研究了海流域各类植物硫元素含量特征及与土壤硫素的关系,结果表明：海河流域植物全硫量平均值为０．２３２％,为正常含量的下限值,与我国南,北方一些地区比较属中等水平,其中栽培植物略高于野生植物,植物硫含量范围差别悬殊,最大值可为最小值的２６倍,以沿大城市的水系和地区的植物含硫量高,海流域的土壤全硫含量平均值为０．０４３％（指耕地和天然植被的土壤）,为正常土壤含量的中上水平,植物硫元素含量与土壤硫含     

电脉冲穿孔法将苏云金杆菌δ-内毒素基因导入野生型芽孢杆菌

利用电脉冲穿孔法将带有苏云金杆菌毒蛋白基因的穿梭质粒导入几株野生型芽孢杆菌中。它们是野生型的蜡状芽孢杆菌、短芽孢杆菌和枯草芽孢杆菌。通过观察在新霉素和氨苄青霉素平板上长出的抗性菌落数,计算出转化效率为10~1—10~4转化子/μgDNA。从转化子中分离到的质粒DNA大小及其用HindⅢ酶切的片段与原始质粒DNA相同,毒性测试表明重组转化子对烟青虫六天的致死率达90—100％。