甘蓝型油菜SAMDC3基因及其启动子的克隆与分析

S-腺苷甲硫氨酸脱羧酶（SAMDC）是植物体内亚精胺和精胺前体物质形成的关键酶。本研究克隆了甘蓝型油菜（Brassica napus）BnSA MDC3基因家族2个成员的全长cDNA和启动子序列,并对其诱导表达特性进行了鉴定。BnSAMDC3—1（GenBank accession No．HM013966）和BnSAMDC3—2（GenBankac．cession No．HM013967）的全长cDNA分别为1746bp和1754bp,开放阅读框（ORF）长度分别为1101bp和1104bp,在大ORF上游132bp处均包含一个171bp的小ORF。BnSAMDC3基因在叶片中表达量较高,受高温和干旱抑制。6-BA、GA,和SA抑制BnSAMDC3—1的表达,而GA,和甘露醇诱导BnSAMDC3—2表达上调。BnSAMDC3基因启动子具有多个与胁迫和激素诱导相关的顺势调控元件,表明BnSAMDC3可能通过ABA、6-BA和SA信号途径介导植物对非生物胁迫的响应。本研究将有助于进一步探讨甘蓝型油菜抗逆的分子机理,为甘蓝型油菜的栽培和品质改良奠定基础。     

Improved drought tolerance of transgenic Zea mays plants that express the glutamate dehydrogenase gene (gdhA) of E. coli

Genetic modification of nitrogen metabolism via bacterial NADPH- dependent glutamate dehydrogenase (GDH; E.C.4.1.2.1) favorably alters growth and metabolism of C3 plants. The aim of this study was to examine the effect of expression of GDH in the cytoplasmic compartment of Zea mays cells. The gdhA gene from Escherichia coli , that encoded a NADPH-GDH, was ligated to the ubiquitin promoter that incorporated the first intron enhancer and used to transform Z. mays cv. ‘H99’ embryo cultures by biolistics. R0–R3 generations included selfed inbreds, back-crossed inbreds, and hybrids with B73 derivatives. The lines with the highest GDH specific activity produced infertile R0 plants. The highest specific activity of GDH from the fertile Z. mays plants was sufficient to alter phenotypes. Plant damage caused by the phosphinothricin in gluphosinate-type herbicides, glutamine synthetase (GS; EC 6.1.3.2) inhibitors, was less pronounced in Z. mays plants with gdhA pat than in gusA pat plants. Germination and grain biomass production were increased in gdhA transgenic plants in the field during seasons with significant water deficits but not over all locations. Water deficit tolerance under controlled conditions was increased. Crops modified with gdhA may have value in semi-arid locations.     

The effect of different nitrogen sources on the symbiotic interaction between Sorghum bicolor and Glomus intraradices: Expression of plant and fungal genes involved in nitrogen assimilation

In the arbuscular mycorrhizal (AM) symbiosis, plants take up part of the nitrogen (N) through a mycorrhizal pathway. In this study, we assessed the effect of different N sources on the expression of genes coding for enzymes and transporters of the mycorrhizal N uptake pathway, using Sorghum bicolor and Glomus intraradices as a model. Some of the genes investigated were differentially regulated in the intraradical and in the extraradical mycelium depending on the N source. In AM roots, some fungal and plant genes were co-regulated, suggesting an interdependence of both partners in the mycorrhizal N uptake pathway. Mycorrhizal N transfer may have a preference for glycine (plant growth and N uptake stimulation).     

枯草芽孢杆菌草酸脱羧酶转化拟南芥研究初报

多种真菌在致病过程中会分泌草酸，这些草酸产生菌寄主范围广，可以导致上百种植物病害，造成世界范围农作物的严重减产。草酸可以通过氧化与脱羧两种途径降解。该研究克隆了枯草芽孢杆菌的草酸脱羧酶基因Yvrk，并构建其植物表达载体，通过农杆菌浸花转化拟南芥，收获种子，用除草剂Basta筛选获得15株转基因植株，对其中的11个株系分别离体接种菌核病菌，24h后量病斑，发现有6株转基因植株的病斑显著小于野生型。PCR验证发现大部分转基因植株确有Yvrk的存在，实验结果说明草酸脱羧酶基因确能一定程度上缓解真菌病害。     

Binary mixtures of pyrethroids produce differential effects on Ca influx and glutamate release at isolated presynaptic nerve terminals from rat brain

Isolated rat brain synaptosomes were used to evaluate the action of pyrethroid mixtures on Ca²⁺ influx and subsequent glutamate release under depolarizing conditions. In equipotent binary mixtures at their respective and/or estimated EC₅₀s with deltamethrin always as one of the two components, cismethrin, λ-cyhalothrin, cypermethrin, esfenvalerate and permethrin were additive and S-bioallethrin, fenpropathrin and tefluthrin were less-than-additive on Ca²⁺ influx. In binary mixtures with deltamethrin always as one of the two components, esfenvalerate, permethrin and tefluthrin were additive and λ-cyhalothrin was less-than-additive on glutamate release. Binary mixture of S-bioallethrin and cismethrin was additive for both Ca²⁺ influx and glutamate release. Only a subset of pyrethroids (S-bioallethrin, cismethrin, cypermethrin, and fenpropathrin) in binary mixtures with deltamethrin caused a more-than-additive effect on glutamate release. These binary mixtures were, however, only additive (cismethrin and cypermethrin) or less-than-additive (S-bioallethrin and fenpropathrin) on Ca²⁺ influx. Therefore, increased glutamate release evoked by this subset of pyrethroids in binary mixture with deltamethrin is not entirely occurring by Ca²⁺-dependent mechanisms via their action at voltage-sensitive calcium channels. These results suggest that pyrethroids do not share a common mode of toxicity at presynaptic nerve terminals from rat brain and appear to affect multiple target sites, including voltage-sensitive calcium, chloride and sodium channels.     

Organophosphorus insecticides affect normal polyamine metabolism in amphibian embryogenesis

The objective of the present study was to evaluate the concentration- and time-dependent effects of the organophosphorus insecticides malathion and azinphos-methyl on polyamine metabolism, and relate them to normal and altered embryonic development of the common toad Rhinella arenarum. Control embryos showed that the higher polyamines spermidine and spermine acquired importance with respect to the diamine putrescine as embryonic development progressed. The activity of ornithine decarboxylase significantly decreased in complete operculum embryos. Continuous exposure to malathion caused a decrease in polyamine levels during embryonic development. However, there was an increase in putrescine levels in complete operculum embryos exposed to a sublethal concentration of the insecticide. Embryos exposed to malathion displayed a decrease in fresh weight and size, along with an increase in the number of malformed individuals. R. arenarum embryos exposed to a lethal concentration of azinphos-methyl showed an increase in putrescine levels and a decrease in spermidine and spermine levels, accompanied by an increase in ornithine decarboxylase activity. In conclusion, as the embryonic development of the toad R. arenarum progresses, polyamine metabolism shifts to higher polyamine levels with a more preponderant contribution of spermidine and spermine with respect to putrescine and involves a dramatic change in ornithine decarboxylase activity, one of the key regulatory enzymes of the pathway. Organophosphorus insecticides are capable of altering polyamine metabolism, slowing embryo development in parallel with a reduction in spermidine and spermine levels. An increase in the oxidative degradation of polyamines might be involved in the toxic action of organophosphorus insecticides and might also be related to other effects such as teratogenesis.     

水稻与黄瓜耐铵性生理分析

本文分析了在不同NH_4~+-N浓度(1、5、10、20 mm0I)处理一周后以水培的水稻与黄瓜叶片生长和氨同化的变化及差异。水稻能在高浓度NH_4~+N(10、20mmol)时良好生长,而黄瓜的叶面积生长量和叶绿素含量均明显减少,此时黄瓜各层叶的谷酰胺合成酶(GS)和谷氨酸脱氢酶(GDH)活力均降低,从而表现出NH_4~+-/(NH_4~+-N+酰胺-N)值的急剧升高;水稻在10和20mmolNH_4~+:N时叶片的GDH仍能保持较大的活力,H_4~+N/(H_4~+-N+酰胺-N)值均较小。结果表明,顶叶的GDH活力与NH_4~+-N/(NH_4~+N+酰胺N)可作为植物耐铵性的生理指标。     

Characterization of mevalonate metabolism in the sea bass (Dicentrarchus labrax L) liver

The activities of mevalonate kinase, mevalonate 5-phosphate kinase and mevalonate 5-pyrophosphate decarboxylase, were examined in sea bass (Dicentrarchus labrax L) liver. The activities of the three enzymes were studiedin vitro in relation to the influence of protein content, time of incubation, pH, temperature, mevalonate, ATP and Mg⁺⁺ concentration. Protein content in the assay medium affected the three enzymes differently. Mevalonate kinase, mevalonate 5-phosphate kinase, and mevalonate 5-pyrophosphate decarboxylase activities were linear up to 0.2, 0.4 and 0.8 mg protein, respectively. With respect to the time course studies, the enzymes also behaved differently. Mevalonate kinase activity increased over forty minutes, reaching a plateau thereafter, while mevalonate 5-phosphate kinase and decarboxylase increased over the entire assay period. All the three enzymes showed a maximum in activity at pH 7.5. The effect of reaction temperature showed that phosphorylation increased to maximum around 35°C for mevalonate kinase and 30°C for mevalonate 5-phosphate kinase while decarboxylation rates remained constant well until 30°C temperature decreasing afterwards. The enzymes behaved differently as a function of mevalonate concentration. Mevalonate 5-phosphate formed was maximal when the initial mevalonate concentration was 272 M, whereas mevalonate 5-pyrophosphate and CO₂ were formed maximally at mevalonate concentrations of 136 M and 68M, respectively. Optimal ATP concentration in the medium was 3 mM for decarboxylase and 6 mM for kinases, and Mg⁺⁺ requirements varied from 4 mM for decarboxylase to 6 mM for kinases.     

多胺跨膜物质转运的机制

多胺具有调控细胞增殖、分化和凋亡的功能,可参与动物繁殖、胚胎发育以及癌症发生发展等多种生物学过程。在动物机体中,多胺稳态是通过多胺跨膜物质转运和多胺代谢途径共同维持的。溶质转运蛋白(SLC)基因家族中的SLC3A2、SLC7A1、SLC12A8、SLC22A16、SLC22A 1、SLC22A 2、SLC22A 3基因及其编码的蛋白质可参与多胺的跨膜物质转运;多胺代谢关键调控基因鸟氨酸脱羧酶(ODC)、鸟氨酸脱羧酶抗酶(OAZ)和鸟氨酸脱羧酶抗酶抑制剂(AZIN)对多胺跨膜物质转运也具有重要的调控功能;此外,金属阳离子、细胞膜跨膜电位和p H等内环境因素也可参与多胺转运的调节。因此,本文就多胺转运蛋白、多胺代谢相关基因和蛋白质以及内环境因素调控多胺跨膜物质转运的分子调控机制作一综述,以期为阐明多胺转运调控机制的研究奠定理论基础。