Opi1 mediates repression of phospholipid biosynthesis by phosphate limitation in the yeast Saccharomyces cerevisiae

Structural genes of phospholipid biosynthesis in the yeast Saccharomyces cerevisiae are transcribed when precursor molecules inositol and choline (IC) are limiting. Gene expression is stimulated by the heterodimeric activator Ino2/Ino4, which binds to ICRE (inositol/choline‐responsive element) promoter sequences. Activation is prevented by repressor Opi1, counteracting Ino2 when high concentrations of IC are available. Here we show that ICRE‐dependent gene activation is repressed not only by an excess of IC but also under conditions of phosphate starvation. While PHO5 is activated by phosphate limitation, INO1 expression is repressed about 10‐fold. Repression of ICRE‐dependent genes by low phosphate is no longer observed in an opi1 mutant while repression is still effective in mutants of the PHO regulon (pho4, pho80, pho81 and pho85). In contrast, gene expression with high phosphate is reduced in the absence of pleiotropic sensor protein kinase Pho85. We could demonstrate that Pho85 binds to Opi1 in vitro and in vivo and that this interaction is increased in the presence of high concentrations of phosphate. Interestingly, Pho85 binds to two separate domains of Opi1 which have been previously shown to recruit pleiotropic corepressor Sin3 and activator Ino2, respectively. We postulate that Pho85 positively influences ICRE‐dependent gene expression by phosphorylation‐dependent weakening of Opi1 repressor, affecting its functional domains required for promoter recruitment and corepressor interaction. Copyright © 2016 John Wiley & Sons, Ltd.     

Modifications of the cell wall of yeasts grown on hexadecane and under starvation conditions

Electron‐microscopic examinations have demonstrated local modifications in the cell wall of the yeast Candida maltosa grown on hexadecane. In our earlier studies, these modified sites, observed in other yeasts grown on oil hydrocarbons, were conventionally called 'canals'. The biochemical and cytochemical studies of C. maltosa have revealed a correlation between the formation of 'canals' and decrease in the amount of cell wall polysaccharides, glucan and mannan. The ultrathin sections and surface replicas have shown that the 'canals' are destroyed by pronase, thus indicating that a significant proportion of their content is represented by proteins. This finding was compatible with our earlier data on the localization of oxidative enzymes in 'canals' and possible participation of the 'canals' in the primary oxidation of hydrocarbons. A completely unexpected and intriguing phenomenon has been the appearance of 'canals' in the yeast C. maltosa under starvation conditions. Unlike the yeasts grown on hexadecane, mannan almost disappears in starving cells, while the quantity of glucan first decreases and then is restored to its initial level. The role of 'canals' in starving cells is as yet unclear; it is assumed that they acquire exoenzymes involved in the utilization of products of cell lysis in the starving population. In the future, 'canals' of starving cells will be studied in connection with their possible participation in apoptosis. Copyright © 2015 John Wiley & Sons, Ltd.     

Starve to Sustain—An Ancient Syrian Landrace of Sorghum as Tool for Phosphorous Bio-Economy?

Phosphorus (P) is an essential macronutrient, playing a role in developmental and metabolic processes in plants. To understand the local and systemic responses of sorghum to inorganic phosphorus (P_i) starvation and the potential of straw and ash for reutilisation in agriculture, we compared two grain (Razinieh) and sweet (Della) sorghum varieties with respect to their morpho-physiological and molecular responses. We found that P_i starvation increased the elongation of primary roots, the formation of lateral roots, and the accumulation of anthocyanin. In Razinieh, lateral roots were promoted to a higher extent, correlated with a higher expression of SbPht1 phosphate transporters. Infrared spectra of straw from mature plants raised to maturity showed two prominent bands at 1371 and 2337 cm⁻¹, which could be assigned to P-H(H₂) stretching vibration in phosphine acid and phosphinothious acid, and their derivates, whose abundance correlated with phosphate uptake of the source plant and genotype (with a higher intensity in Razinieh). The ash generated from these straws stimulated the shoot elongation and root development of the rice seedlings, especially for the material derived from Razinieh raised under P_i starvation. In conclusion, sorghum growing on marginal lands has potential as a bio-economy alternative for mineral phosphorus recycling.     

表面织构及供油量对润滑性能影响的建模分析

目的研究不同供油条件下织构表面的润滑性能。方法首先,建立考虑表面织构的乏油润滑模型,求解修正雷诺方程获得乏油工况下考虑织构表面的润滑油膜厚度以及压力分布。然后,依据求得的润滑油膜厚度判断计算域内各点润滑状态,通过接触压力及油膜厚度分别计算边界润滑、混合润滑以及流体润滑状态下的切应力,并积分求得摩擦力进而得到摩擦系数。结果模拟了供油层厚度为50~500 nm以及充分供油条件下三种织构的润滑行为,获得了不同润滑状态下表面织构的摩擦系数。速度为0.1 m/s时,供油量对接触区油膜厚度的影响较小,不同润滑状态下织构表现出不同的润滑性能。速度为0.2 m/s时,供油层厚度对油膜厚度的影响较大,随着供油层厚度的增大,膜厚明显增加,摩擦系数在供油层厚度为200 nm时最小。结论接触副处于流体润滑状态时,织构表面不具有减摩效果。接触副处于边界润滑状态时,织构表面具有减摩效果,并且织构较密时,摩擦系数较小。接触副处于混合润滑状态时,织构过于稀疏或密集时均不具有减摩效果,但是合理分布的织构具有减摩效果。     

Ti4O7 supported IrOx for anode reversal tolerance in proton exchange membrane fuel cell

Fuel starvation can occur and cause damage to the cell when proton exchange membrane fuel cells operate under complex working conditions. In this case, carbon corrosion occurs. Oxygen evolution reaction (OER) catalysts can alleviate carbon corrosion by introducing water electrolysis at a lower potential at the anode in fuel shortage. The mixture of hydrogen oxidation reaction (HOR) and unsupported OER catalyst not only reduces the electrolysis efficiency, but also influences the initial performance of the fuel cell. Herein, Ti₄O₇ supported IrO_x is synthesized by utilizing the surfactant-assistant method and serves as reversal tolerant components in the anode. When the cell reverse time is less than 100 min, the cell voltage of the MEA added with IrO_x/Ti₄O₇ has almost no attenuation. Besides, the MEA has a longer reversal time (530 min) than IrO_x (75 min), showing an excellent reversal tolerance. The results of electron microscopy spectroscopy show that IrO_x particles have a good dispersity on the surface of Ti₄O₇ and IrO_x/Ti₄O₇ particles are uniformly dispersed on the anode catalytic layer. After the stability test, the Ti₄O₇ support has little decay, demonstrating a high electrochemical stability. IrO_x/Ti₄O₇ with a high dispersity has a great potential to the application on the reversal tolerance anode of the fuel cell.     

Solving the Task Starvation and Resources Problem Using Optimized SMPIA in Cloud

In this study, a new feature is added to the smart message passing interface (SMPI) approach (SMPIA) based on the prioritization method, which can completely eliminate the task starvation and lack of sufficient resources problems through prioritizing the tasks. The proposed approach is based on prioritizing the tasks and the urgency of implementation. Tasks are prioritized based on execution time, workload, the task with a more sensitive priority is executed earlier by the free source. The idea of demand-bound functions (DBFs) was extended to the SMPIA setting based on partitions and caps. For each task, two DBFs are constructed, DBFLOand DBFHI, for the LO and HI criticality modes, respectively. The simulation results returned by MATLAB showed that with the optimized SMPIA (O-SMPIA), the parameters of maximum service execution time, response time, delay time, and throughput improved in this work. In addition, the results confirmed that the reduction of execution time, completion time, and resource consumption time did not affect the response time and throughput of workflow tasks and did not cause inefficient use of resources in virtual machines (VMs) and data centers (DCs). The evaluation of performance metrics showed that the delay, response time of the Greedy algorithm was less than that of Max-Min and Min-Min. At the same time, the execution time of Max-Min was less than the others and the throughput of the Greedy was longer. The effect and throughput of O-SMPIA became more obvious as change to the job count and the number of cloud workloads increased. It is also worth mentioning that one of the main advantages of the O-SMPIA to other methods is the efficient use of time to execute all the defined tasks by CPU.     

Experimental study and mitigation of abnormal behavior of cell voltage in a proton exchange membrane fuel cell stack

The aim of this study is to investigate the abnormal behavior of cell voltage in a proton exchange membrane fuel cell stack and a mitigation strategy. The proposed strategy is simple and requires only a three‐way solenoid valve to replace the direct way solenoid valve of the original system. It is applied to a proton exchange membrane fuel cell stack with a dead‐ended anode to verify its validity. The behavior of the cell voltages in the stack is discussed in detail, especially the cell reversal process. The results show that the proposed strategy can significantly reduce the severity of hydrogen starvation. And the maximum power of the stack is increased by 10.67%. It is a sudden increase related to cell reversal mitigation. Uneven hydrogen distribution is the cause of low cell voltage and cell reversal. This strategy increases the cell voltage by increasing the hydrogen content in the anode flow channel downstream. It also significantly reduces the fluctuations in cell voltage and improves the uniformity of the cell voltage. This experimental study contributes to mitigate hydrogen starvation in cells of proton exchange membrane fuel cell stacks in application.     

Characterization methodology for anode starvation in HT-PEM fuel cells

Degradation caused by fuel starvation may be an important reason for limited fuel cell lifetimes. In this work, we present an analytical characterization of the high temperature polymer exchange membrane fuel cell (HT-PEM FC) behavior under cycled anode starvation and subsequent regeneration conditions to investigate the impact of degradation due to H₂ starvation. Two membrane electrode assemblies (MEAs) with an active area of 21 cm² were operated of up to 550 min, which included up to 14 starvation/regeneration cycles. Overall cell voltage as well as current density distribution (S⁺⁺ unit) were measured simultaneously each minute during FC operation. The cyclicity of experiments was used to check the long term durability of the HT-PEM FC. After FC operation, micro-computed tomography (μ-CT) was applied to evaluate the influence of starvation on anode and cathode catalyst layer thicknesses.During starvation, cell voltage and current density distribution over the active area of the MEA significantly differed from nominal conditions. A significant drop in cell voltage from 0.6 to 0.1 V occurred after approx. 20 min for the first starvation step, and after 10 min for all subsequent starvation steps. By contrast, the voltage response is immediately stable at 0.6 V during every regeneration step. During each starvation, the local current density reached up to 0.3 A∙point⁻¹ at the area near the gas inlet (9 cm²) while near the outlet it drops to 0.01 A∙point⁻¹. The deviation from a balanced current density distribution occurred after 10 min for the first starvation step, and after ca. 2 min for the subsequent starvation steps. Hence, compared to the voltage drop, the deviation from a balanced current density distribution always starts earlier. This indicates that the local current density distribution is more sensitive to local changes in the MEA than overal cell voltage drop. This finding may help to prevent undesirable influences of the starvation process.The μ-CT images showed that H₂ starvation lead to thickness decrease of ca. 20–30% in both anode and cathode catalyst layers compared to a fresh MEA. Despite of the 14 starvation steps and the thinning of the catalyst layers the MEA presents stable cell voltage during regeneration.     

混合能源直流微电网能源优化管控策略研究

混合能源直流微电网在快速跟踪负载方面具有较大优势,弥补了固体氧化物燃料电池(solid oxide fuel cell, SOFC)直流微电网功率跟踪缓慢的问题。现有能源管控策略重点关注能源分配,对系统效率、运行安全性和燃料亏空方面缺乏相关研究和成熟策略。为此,提出了一种混合能源直流微型电网能源优化管控策略。首先,搭建了混合SOFC直流微电网模型。其次,采用最优操作点(optimal operating points, OOPs)实现最大效率,然后采用平均电流控制模式保证稳定的电力供应。最后,设计了基于SOFC电流的时滞控制算法来避免燃料亏空。实验结果表明,所提出的能源优化管控策略具有时间响应迅速、输出效率高和热特性良好等优势。     

Enhanced Autophagic Activity Improved the Root Growth and Nitrogen Utilization Ability of Apple Plants under Nitrogen Starvation

Autophagy is a conserved degradation pathway for recycling damaged organelles and aberrant proteins, and its important roles in plant adaptation to nutrient starvation have been generally reported. Previous studies found that overexpression of autophagy-related (ATG) gene MdATG10 enhanced the autophagic activity in apple roots and promoted their salt tolerance. The MdATG10 expression was induced by nitrogen depletion condition in both leaves and roots of apple plants. This study aimed to investigate the differences in the growth and physiological status between wild type and MdATG10-overexpressing apple plants in response to nitrogen starvation. A hydroponic system containing different nitrogen levels was used. The study found that the reduction in growth and nitrogen concentrations in different tissues caused by nitrogen starvation was relieved by MdATG10 overexpression. Further studies demonstrated the increased root growth and the higher nitrogen absorption and assimilation ability of transgenic plants. These characteristics contributed to the increased uptake of limited nitrogen nutrients by transgenic plants, which also reduced the starvation damage to the chloroplasts. Therefore, the MdATG10-overexpressing apple plants could maintain higher photosynthetic ability and possess better growth under nitrogen starvation stress.