Ubiquitination pathway as a target to develop abiotic stress tolerance in rice

Abiotic stresses may result in significant losses in rice grain productivity. Protein regulation by the ubiquitin/proteasome system has been studied as a target mechanism to optimize adaptation and survival strategies of plants to different environmental stresses. This article aimed at highlighting recent discoveries about the roles ubiquitination may play in the exposure of rice plants to different abiotic stresses, enabling the development of modified plants tolerant to stress. Responses provided by the ubiquitination process include the regulation of the stomatal opening, phytohormones levels, protein stabilization, cell membrane integrity, meristematic cell maintenance, as well as the regulation of reactive oxygen species and heavy metals levels. It is noticeable that ubiquitination is a potential means for developing abiotic stress tolerant plants, being an excellent alternative to rice (and other cultures) improvement programs.     

Formation of Thick Dense Yttrium Iron Garnet Films Using Aerosol Deposition

Aerosol deposition (AD) is a thick-film deposition process that can produce layers up to several hundred micrometers thick with densities greater than 95% of the bulk. The primary advantage of AD is that the deposition takes place entirely at ambient temperature; thereby enabling film growth in material systems with disparate melting temperatures. This report describes in detail the processing steps for preparing the powder and for performing AD using the custom-built system. Representative characterization results are presented from scanning electron microscopy, profilometry, and ferromagnetic resonance for films grown in this system. As a representative overview of the capabilities of the system, focus is given to a sample produced following the described protocol and system setup. Results indicate that this system can successfully deposit 11 µm thick yttrium iron garnet films that are  > 90% of the bulk density during a single 5 min deposition run. A discussion of methods to afford better control of the aerosol and particle selection for improved thickness and roughness variations in the film is provided.     

A Simple and Inexpensive Method for Determining Cold Sensitivity and Adaptation in Mice

Cold hypersensitivity is a serious clinical problem, affecting a broad subset of patients and causing significant decreases in quality of life. The cold plantar assay allows the objective and inexpensive assessment of cold sensitivity in mice, and can quantify both analgesia and hypersensitivity. Mice are acclimated on a glass plate, and a compressed dry ice pellet is held against the glass surface underneath the hindpaw. The latency to withdrawal from the cooling glass is used as a measure of cold sensitivity.Cold sensation is also important for survival in regions with seasonal temperature shifts, and in order to maintain sensitivity animals must be able to adjust their thermal response thresholds to match the ambient temperature. The Cold Plantar Assay (CPA) also allows the study of adaptation to changes in ambient temperature by testing the cold sensitivity of mice at temperatures ranging from 30 °C to 5 °C. Mice are acclimated as described above, but the glass plate is cooled to the desired starting temperature using aluminum boxes (or aluminum foil packets) filled with hot water, wet ice, or dry ice. The temperature of the plate is measured at the center using a filament T-type thermocouple probe. Once the plate has reached the desired starting temperature, the animals are tested as described above.This assay allows testing of mice at temperatures ranging from innocuous to noxious. The CPA yields unambiguous and consistent behavioral responses in uninjured mice and can be used to quantify both hypersensitivity and analgesia. This protocol describes how to use the CPA to measure cold hypersensitivity, analgesia, and adaptation in mice.     

Microsecond simulations of the folding/unfolding thermodynamics of the Trp‐cage miniprotein

We study the unbiased folding/unfolding thermodynamics of the Trp‐cage miniprotein using detailed molecular dynamics simulations of an all‐atom model of the protein in explicit solvent using the Amberff99SB force field. Replica‐exchange molecular dynamics simulations are used to sample the protein ensembles over a broad range of temperatures covering the folded and unfolded states at two densities. The obtained ensembles are shown to reach equilibrium in the 1 μs/replica timescale. The total simulation time used in the calculations exceeds 100 μs. Ensemble averages of the fraction folded, pressure, and energy differences between the folded and unfolded states as a function of temperature are used to model the free energy of the folding transition, ΔG(P, T), over the whole region of temperatures and pressures sampled in the simulations. The ΔG(P, T) diagram describes an ellipse over the range of temperatures and pressures sampled, predicting that the system can undergo pressure‐induced unfolding and cold denaturation at low temperatures and high pressures, and unfolding at low pressures and high temperatures. The calculated free energy function exhibits remarkably good agreement with the experimental folding transition temperature (T_f = 321 K), free energy, and specific heat changes. However, changes in enthalpy and entropy are significantly different than the experimental values. We speculate that these differences may be due to the simplicity of the semiempirical force field used in the simulations and that more elaborate force fields may be required to describe appropriately the thermodynamics of proteins. Proteins 2010. © 2010 Wiley‐Liss, Inc.     

Rapid cooling triggers forisome dispersion just before phloem transport stops

Phloem transport stops transiently within dicot stems that are cooled rapidly, but the cause remains unknown. Now it is known that (1) rapid cooling depolarizes cell membranes giving a transient increase in cytoplasmic Ca²⁺, and (2) a rise of free calcium triggers dispersion of forisomes, which then occlude sieve elements (SEs) of fabacean plants. Therefore, we compared the effects of rapid chilling on SE electrophysiology, phloem transport and forisomes in Vicia faba. Forisomes dispersed after rapid cooling with a delay that was longer for slower cooling rates. Phloem transport stopped about 20 s after forisome dispersion, and then transport resumed and forisomes re‐condensed within similar time frames. Transport interruption and forisome dispersion showed parallel behaviour – a cooling rate‐dependent response, transience and desensitization. Chilling induced both a fast and a slow depolarization of SE membranes, the electrical signature suggesting strongly that the cause of forisome dispersion was the transient promotion of SE free calcium. This apparent block of SEs by dispersed forisomes may be assisted by other Ca²⁺‐dependent sealing proteins that are present in all dicots.     

Body proportions of circumpolar peoples as evidenced from skeletal data: Ipiutak and Tigara (Point Hope) versus Kodiak Island Inuit

Given the well‐documented fact that human body proportions covary with climate (presumably due to the action of selection), one would expect that the Ipiutak and Tigara Inuit samples from Point Hope, Alaska, would be characterized by an extremely cold‐adapted body shape. Comparison of the Point Hope Inuit samples to a large (n > 900) sample of European and European‐derived, African and African‐derived, and Native American skeletons (including Koniag Inuit from Kodiak Island, Alaska) confirms that the Point Hope Inuit evince a cold‐adapted body form, but analyses also reveal some unexpected results. For example, one might suspect that the Point Hope samples would show a more cold‐adapted body form than the Koniag, given their more extreme environment, but this is not the case. Additionally, univariate analyses seldom show the Inuit samples to be more cold‐adapted in body shape than Europeans, and multivariate cluster analyses that include a myriad of body shape variables such as femoral head diameter, bi‐iliac breadth, and limb segment lengths fail to effectively separate the Inuit samples from Europeans. In fact, in terms of body shape, the European and the Inuit samples tend to be cold‐adapted and tend to be separated in multivariate space from the more tropically adapted Africans, especially those groups from south of the Sahara. Am J Phys Anthropol, 2010. © 2009 Wiley‐Liss, Inc.     

兴奋性氨基酸受体的激活介导冷水应激诱导的tau蛋白磷酸化

为探讨兴奋性神经传递系统是否参与冷水应激引起的tau蛋白磷酸化,将小鼠于4℃冷水应激5min.采用免疫印迹和免疫组织化学方法分析应激后脑内c-fos和磷酸化tau蛋白的表达情况;运用HPLC检测冷水应激后小鼠脑内兴奋性或抑制性神经递质的变化;同时分析兴奋性氨基酸受体和L-型钙通道拮抗剂预处理后冷水应激小鼠脑内磷酸化tau蛋白的水平.冷水应激后1h,海马内磷酸化tau蛋白的水平显著升高,同时伴c-fos的染色增加.HPLC检测显示,兴奋性和抑制性神经递质呈现急剧上升而后又下降的趋势.冷水应激后15min,天冬氨酸和甘氨酸水平显著升高,1h后天冬氨酸、谷氨酸、牛磺酸和γ-氨基丁酸显著下降.NMDA受体拮抗剂MK-801(5mg/kg)和AMPA受体拮抗剂DNQX(0.5,5mg/kg)可显著抑制冷水应激引起的磷酸化tau蛋白水平的升高,代谢性谷氨酸受体拮抗剂MAP-4不影响tau蛋白的磷酸化,另外,L-型钙通道阻断剂尼莫地平可抑制冷水应激引起的磷酸化tau蛋白水平的升高.这些结果表明,冷水应激可影响兴奋性神经传递系统,通过离子型兴奋性氨基酸受体和异常神经激活来调节tau蛋白的磷酸化.兴奋性神经传递系统的激活在冷水...     

寒冷诱导产热时大鼠棕色脂肪能量代谢相关蛋白谱的变化

棕色脂肪组织(BAT)的生理作用与白色脂肪显著不同,它以产热的形式释放能量而不是将能量以ATP的形式储存．线粒体是在能量代谢和维持细胞稳态中具有重要功能的细胞器．为了更好地了解棕色脂肪中的能量代谢过程,运用双向电泳及质谱相结合的技术,分离了大鼠白色和棕色脂肪线粒体,对其差异蛋白质谱进行了系统分析和鉴定．参与脂肪和氨基酸代谢、三羧酸循环及线粒体呼吸链的蛋白质在棕色脂肪线粒体中的表达明显高于白色脂肪线粒体,在寒冷诱导下这些蛋白质的表达进一步上调．此外,参与辅酶Q合成的一系列COQ 基因在棕色脂肪中经寒冷适应后表达明显上调．该研究表明,辅 酶Q合成的增高在非颤栗性产热中具有重要作用,为进一步了解棕色脂肪特异性的能量代谢提供了新的思路．