Rice ubiquitin-conjugating enzyme OsUbc13 negatively regulates immunity against pathogens by enhancing the activity of OsSnRK1a

Ubc13 is required for Lys63-linked polyubiquitination and innate immune responses in mammals, but its functions in plant immunity still remain largely unknown. Here, we used molecular biological, pathological, biochemical, and genetic approaches to evaluate the roles of rice OsUbc13 in response to pathogens. The OsUbc13-RNA interference (RNAi) lines with lesion mimic phenotypes displayed a significant increase in the accumulation of flg22- and chitin-induced reactive oxygen species, and in defence-related genes expression or hormones as well as resistance to Magnaporthe oryzae and Xanthomonas oryzae pv oryzae. Strikingly, OsUbc13 directly interacts with OsSnRK1a, which is the α catalytic subunit of SnRK1 (sucrose non-fermenting-1-related protein kinase-1) and acts as a positive regulator of broad-spectrum disease resistance in rice. In the OsUbc13-RNAi plants, although the protein level of OsSnRK1a did not change, its activity and ABA sensitivity were obviously enhanced, and the K63-linked polyubiquitination was weaker than that of wild-type Dongjin (DJ). Overexpression of the deubiquitinase-encoding gene OsOTUB1.1 produced similar effects with inhibition of OsUbc13 in affecting immunity responses, M. oryzae resistance, OsSnRK1a ubiquitination, and OsSnRK1a activity. Furthermore, re-interfering with OsSnRK1a in one OsUbc13-RNAi line (Ri-3) partially restored its M. oryzae resistance to a level between those of Ri-3 and DJ. Our data demonstrate OsUbc13 negatively regulates immunity against pathogens by enhancing the activity of OsSnRK1a.     

DNA barcoding of Cymbidium by genome skimming: Call for next-generation nuclear barcodes

Cymbidium is an orchid genus that has undergone rapid radiation and has high ornamental, economic, ecological and cultural importance, but its classification based on morphology is controversial. The plastid genome (plastome), as an extension of plant standard DNA barcodes, has been widely used as a potential molecular marker for identifying recently diverged species or complicated plant groups. In this study, we newly generated 237 plastomes of 50 species (at least two individuals per species) by genome skimming, covering 71.4% of members of the genus Cymbidium. Sequence-based analyses (barcoding gaps and automatic barcode gap discovery) and tree-based analyses (maximum likelihood, Bayesian inference and multirate Poisson tree processes model) were conducted for species identification of Cymbidium. Our work provides a comprehensive DNA barcode reference library for Cymbidium species identification. The results show that compared with standard DNA barcodes (rbcL + matK) as well as the plastid trnH-psbA, the species identification rate of the plastome increased moderately from 58% to 68%. At the same time, we propose an optimized identification strategy for Cymbidium species. The plastome cannot completely resolve the species identification of Cymbidium, the main reasons being incomplete lineage sorting, artificial cultivation, natural hybridization and chloroplast capture. To further explore the potential use of nuclear data in identifying species, the Skmer method was adopted and the identification rate increased to 72%. It appears that nuclear genome data have a vital role in species identification and are expected to be used as next-generation nuclear barcodes.     

Influence of root density on the critical soil water potential

Estimation of root water uptake in crops is important for making many other agricultural predictions. This estimation often involves two assumptions: (1) that a critical soil water potential exists which is constant for a given combination of soil and crop and which does not depend on root length density, and (2) that the local root water uptake at given soil water potential is proportional to root length density. Recent results of both mathematical modeling and computer tomography show that these assumptions may not be valid when the soil water potential is averaged over a volume of soil containing roots. We tested these assumptions for plants with distinctly different root systems. Root water uptake rates and the critical soil water potential values were determined in several adjacent soil layers for horse bean (Vicia faba) and oat (Avena sativa) grown in lysimeters, and for field-grown cotton (Gossypium L.), maize (Zea mays) and alfalfa (Medicago sativa L.) crops. Root water uptake was calculated from the water balance of each layer in lysimeters. Water uptake rate was proportional to root length density at high soil water potentials, for both horse bean and oat plants, but root water uptake did not depend on root density for horse bean at potentials lower than −25 kPa. We observed a linear dependency of a critical soil water potential on the logarithm of root length density for all plants studied. Soil texture modified the critical water potential values, but not the linearity of the relationship. B E Clothier Section editor     

中国苏铁属花粉形态研究

对中国苏铁属花粉进行了光镜和扫描电镜观察。花粉中等大,极轴长２６．５－３５．７μｍ,赤道轴长２０．６－２６．４μｍ;极面观椭圆形至近圆形,赤道面观船形或肾形,具远极单沟,达两端,其开闭和形状随花粉干燥或潮湿而变化,内部具多种不规则突起,两端具皱纹;远极面外壁光滑或稀具微突起,近极面具穿孔,孔穴或蜂窝状纹饰。     

Screening of glucose isomerase-producing microorganisms

The ability to convert D-glucose into D-fructose was found in 14 out of 74 species of actinomycetes and bacteria tested. High intracellular glucose isomerase activity was displayed by Arthrobacter sp. and actinomycetes Streptomyces viridobrunneus, Streptomyces sp. 1 and Streptomyces sp. 32. The first showed maximal glucose-converting potential when cultured in both glucose and xylose media, while glucose isomerase activity of Streptomyces species could be found solely in medium supplemented with xylose. The ketose enzymatically formed from D-glucose was identified as D-fructose.     

EB病毒BNLF-1基因的分子生物学研究进展

位于EB病毒基因组U₅-TR区内的BNLF-1基因,其转译产物为潜伏膜蛋白(latent membrane protein1, LMP-1),由于LMP-1可以导致细胞转化并在EB病毒致癌过程中具有重要作用,因而成为近年来EB病毒分子生物学及相关肿瘤如人鼻咽癌、伯基特淋巴瘤、何杰金氏病等疾病病因发病学研究的热点,并取得了一批有重要意义的成果,文章从BNLF-1的基因结构及表达调控, LMP蛋白的结构及生化功能, LMP-1的生物学功能和LMP-1研究进行评述.     

Changes of intracellular Na+ concentration in erythrocytes caused by pulsed electrical field

Changes of sodium ionic concentration of human erythrocytes applied to pulsed electrical field (PEF) were studied by using shift reagent and NMR spectroscopy. The results show that the concentration of intracellular Na⁺ increases with the increasing intensity of PEF when the erythrocytes are applied to PEF with higher intensities. The relationship between intracellular Na concentrations and the intensities of PEF does not follow linear or exponen-tial behavior. As the intensities increase, the intracellular Na⁺concentrations increase even faster by an exponential curve. However under effects of PEF at lower intensities, intracellular Na⁺ concentration decreases. Ouabain can in-hibit the decrease of intracellular Na concentration, and the inhibition increases with the increasing concentration of ouabain, suggesting that Na⁺ , K⁺ -ATPase on cell membrane can be activated by PEF at lower intensities. Direct measurement of activities of the enzyme by using Malachite green method has confirmed this observation. Cell perme-abilities to ions, activation of enzymes by electrical fields and transmission of physical signals like PEF across cell mem-branes are discussed.     

蜘蛛杀虫肽基因的合成及其在植物中表达质粒的构建

近年来用生物制剂防治害虫,虽然可以避免环境污染,但效果往往不稳定,而用基因工程方法,将抗虫基因导入植物的基因组中,让植物自身产生抗虫物质,将是一种理想的途径［１,２］。抗虫的植物基因工程主要是利用苏云金杆菌的内毒素蛋白,转化此基因的烟草和番茄显示了对虫的抗性［３—６］。澳大利亚Ｄｅａｋｉｎ大学从一种蜘蛛毒液中分离纯化到一种只有３７个氨基酸的小肽,体外实验发现其能杀死多种对农业生产有害的昆虫,但对哺乳动物没有毒害作用［７］。我们根据此肽的氨基酸序列,采用植物偏爱的密码子,人工合成并克隆了此肽的基因…     

Wiener analysis of spike transmission by identified molluscan neurons

A mathematical model of spike train transmission by identified molluscan neurons was obtained by Wiener analysis. Poisson-distributed sequences of near-threshold stimuli were used as input trains for model construction and testing. Assuming that the error of describing responses of the synapse-neuron system purely by mean outflow frequency is 100%, addition of a linear component to the equation of the model reduces this error to 25%, and addition of a term allowing for nonlinear properties of the system reduces it to 16%. Comparison of the standard error of predicted responses of the model to testing stimulus trains and of responses of a real neuron to these same trains showed that the prediction error with allowance for nonlinear properties does not exceed 21%. Choice of adequate criteria for comparing model and experimental results is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 16, No. 1, pp. 49–54, January–February, 1984.     

Conducting pathways of the rabbit lumbar sympathetic ganglia

Conducting pathways of ganglia from the lumbar portion (L₃–L₅) of the sympathetic trunk in rabbits were studied by recording action potentials from nerves of the ganglia evoked by stimulation of other nerves of these ganglia, and by intracellular recording from single neurons. Besides the well-known system of descending preganglionic fibers, which enter the trunk through white rami communicantes and, as they pass through the ganglia, form synapses on ganglionic neurons, some preganglionic fibers were shown to enter the sympathetic chain through gray rami communicantes and to run in both ascending and descending directions, forming synaptic connections with neurons of the lumbar ganglia.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 16, No. 2, pp. 247–254, March–April, 1984.