Colchicine modulates calcium homeostasis and electrical property of HL‐1 cells

Colchicine is a microtubule disruptor that reduces the occurrence of atrial fibrillation (AF) after an operation or ablation. However, knowledge of the effects of colchicine on atrial myocytes is limited. The aim of this study was to determine if colchicine can regulate calcium (Ca²⁺) homeostasis and attenuate the electrical effects of the extracellular matrix on atrial myocytes. Whole‐cell clamp, confocal microscopy with fluorescence, and western blotting were used to evaluate the action potential and ionic currents of HL‐1 cells treated with and without (control) colchicine (3 nM) for 24 hrs. Compared with control cells, colchicine‐treated HL‐1 cells had a longer action potential duration with smaller intracellular Ca²⁺ transients and sarcoplasmic reticulum (SR) Ca²⁺ content by 10% and 47%, respectively. Colchicine‐treated HL‐1 cells showed a smaller L‐type Ca²⁺ current, reverse mode sodium–calcium exchanger (NCX) current and transient outward potassium current than control cells, but had a similar ultra‐rapid activating outward potassium current and apamin‐sensitive small‐conductance Ca²⁺‐activated potassium current compared with control cells. Colchicine‐treated HL‐1 cells expressed less SERCA2a, total, Thr17‐phosphorylated phospholamban, Cav1.2, CaMKII, NCX, Kv1.4 and Kv1.5, but they expressed similar levels of the ryanodine receptor, Ser16‐phosphorylated phospholamban and Kv4.2. Colchicine attenuated the shortening of the collagen‐induced action potential duration in HL‐1 cells. These findings suggest that colchicine modulates the atrial electrical activity and Ca²⁺ regulation and attenuates the electrical effects of collagen, which may contribute to its anti‐AF activity.     

Morphological,Molecular and Pathological Characterization of Phytophthora amaranthi sp. nov. from Amaranth in Taiwan

In the spring of 2007, a serious disease on amaranth was noticed in several farms in the major amaranth production area in central Taiwan. Abundant oospores were found in the disease tissues. A species of Phytophthora was consistently isolated from disease tissues. The organism formed abundant oospores with smooth walls and with amphigynous antheridia in single culture. Sporangia were partially deciduous with short‐ to medium‐length pedicels. Morphological characteristics of this organism did not match any reported Phytophthora species, and the organism was named Phytophthora amaranthi. Pathogenicity tests and molecular characterization confirmed the identity of the organism as a new pathogen of amaranth and a new species of Phytophthora.     

ENSO and NAO affect long‐term leaf litter dynamics and stoichiometry of Scots pine and European beech mixedwoods

Litterfall dynamics (production, seasonality and nutrient composition) are key factors influencing nutrient cycling. Leaf litter characteristics are modified by species composition, site conditions and water availability. However, significant evidence on how large‐scale, global circulation patterns affect ecophysiological processes at tree and ecosystem level remains scarce due to the difficulty in separating the combined influence of different factors on local climate and tree phenology. To fill this gap, we studied links between leaf litter dynamics with climate and other forest processes, such as tree‐ring width (TRW) and intrinsic water‐use efficiency (iWUE) in two mixtures of Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) in the south‐western Pyrenees. Temporal series (18 years) of litterfall production and elemental chemical composition were decomposed following the ensemble empirical mode decomposition method and relationships with local climate, large‐scale climatic indices, TRW and Scots pine's iWUE were assessed. Temporal trends in N:P ratios indicated increasing P limitation of soil microbes, thus affecting nutrient availability, as the ecological succession from a pine‐dominated to a beech‐dominated forest took place. A significant influence of large‐scale patterns on tree‐level ecophysiology was explained through the impact of the North Atlantic Oscillation (NAO) and El Niño–Southern Oscillation (ENSO) on water availability. Positive NAO and negative ENSO were related to dry conditions and, consequently, to early needle shedding and increased N:P ratio of both species. Autumn storm activity appears to be related to premature leaf abscission of European beech. Significant cascading effects from large‐scale patterns on local weather influenced pine TRW and iWUE. These variables also responded to leaf stoichiometry fallen 3 years prior to tree‐ring formation. Our results provide evidence of the cascading effect that variability in global climate circulation patterns can have on ecophysiological processes and stand dynamics in mixed forests.     

Structural analysis of chloroplast tail‐anchored membrane protein recognition by ArsA1

In mammals and yeast, tail‐anchored (TA) membrane proteins destined for the post‐translational pathway are safely delivered to the endoplasmic reticulum (ER) membrane by a well‐known targeting factor, TRC40/Get3. In contrast, the underlying mechanism for translocation of TA proteins in plants remains obscure. How this unique eukaryotic membrane‐trafficking system correctly distinguishes different subsets of TA proteins destined for various organelles, including mitochondria, chloroplasts and the ER, is a key question of long standing. Here, we present crystal structures of algal ArsA1 (the Get3 homolog) in a distinct nucleotide‐free open state and bound to adenylyl‐imidodiphosphate. This approximately 80‐kDa protein possesses a monomeric architecture, with two ATPase domains in a single polypeptide chain. It is capable of binding chloroplast (TOC34 and TOC159) and mitochondrial (TOM7) TA proteins based on features of its transmembrane domain as well as the regions immediately before and after the transmembrane domain. Several helices located above the TA‐binding groove comprise the interlocking hook‐like motif implicated by mutational analyses in TA substrate recognition. Our data provide insights into the molecular basis of the highly specific selectivity of interactions of algal ArsA1 with the correct sets of TA substrates before membrane targeting in plant cells.     

温度对取食玉米籽粒桃蛀螟生长发育、存活和生殖的影响

为了明确不同温度对取食玉米籽粒桃蛀螟生长发育、存活和生殖的影响,本研究依据年龄-龄期两性生命表理论计算了在21、24、27和30 ℃下取食玉米籽粒的桃蛀螟种群的生命表参数,并基于这些参数预测了未来80 d的种群动态。结果表明: 在21、24、27和30 ℃下桃蛀螟均能完成1个世代,随着温度升高,各阶段的发育历期缩短,且温度间差异显著。24 ℃下的平均单雌产卵量最高(116.7粒),成虫前期存活率最高(84.7%),雌虫占比最高(0.46),均显著高于其他温度。24、27、30 ℃下种群的内禀增长率分别为0.1059、0.1101、0.1045 d^-1,周限增长率分别为1.1117、1.1164、1.1102 d^-1,处理间差异不显著,但均显著高于21 ℃处理。21、24、27和30 ℃下的净增殖率(R₀)分别为17.3、53.7、36.9、19.8个后代个体,其中24 ℃时的R₀最高且显著高于其他温度处理。表明桃蛀螟种群在24～27 ℃下的存活率高、繁殖力大、雌性占比较高,是其生长发育、生存和繁殖的适合温度。     

The structural interpretations of residue Ser297 in catalytic efficiency of Escherichia coli phenylalanine aminotransferase

Escherichia coli phenylalanine aminotransferase (ecPheAT) catalyzes the biosynthesis of phenylalanine and tyrosine. The crystal structure of ecPheAT was determined in our previous study. The comparison of the 3-D structure of several aminotransferases revealed that the residue at position 297 plays an important role in enzyme function. Analysis of activities and kinetic parameters of wild type and mutant ecPheATs suggested that the residue Ser(297) was structurally selected for better catalytic efficiency. Computational modeling of ecPheAT mutants further suggested that Ser in position 297 could make ecPheAT easy with change of conformation from open form to closed form.     

Discoidin domain receptor 2 interacts with Src and Shc following its activation by type I collagen

Discoidin domain receptor 2 (DDR2) is an unusual receptor tyrosine kinase in that its ligand is fibrillar collagen rather than a growth factor-like peptide. We examined signal transduction pathways of DDR2. Here we show that DDR2 is also unusual in that it requires Src activity to be maximally tyrosine-phosphorylated, and that Src activity also promotes association of DDR2 with Shc. The interaction with Shc involves a portion of Shc not previously implicated in interaction with receptor tyrosine kinases. These results identify Src kinase and the adaptor protein Shc as key signaling intermediates in DDR2 signal transduction. Furthermore, Src is required for DDR2-mediated transactivation of the matrix metalloproteinase-2 promoter. The data support a model in which Src and the DDR2 receptor cooperate in a regulated fashion to direct the phosphorylation of both the receptor and its targets.     

Thin‐Film Solar Cells with InP Absorber Layers Directly Grown on Nonepitaxial Metal Substrates

The design and performance of solar cells based on InP grown by the nonepitaxial thin‐film vapor–liquid–solid (TF‐VLS) growth technique is investigated. The cell structure consists of a Mo back contact, p‐InP absorber layer, n‐TiO₂ electron selective contact, and indium tin oxide transparent top electrode. An ex situ p‐doping process for TF‐VLS grown InP is introduced. Properties of the cells such as optoelectronic uniformity and electrical behavior of grain boundaries are examined. The power conversion efficiency of first generation cells reaches 12.1% under simulated 1 sun illumination with open‐circuit voltage (V_OC) of 692 mV, short‐circuit current (J_SC) of 26.9 mA cm^?2, and fill factor (FF) of 65%. The FF of the cell is limited by the series resistances in the device, including the top contact, which can be mitigated in the future through device optimization. The highest measured V_OC under 1 sun is 692 mV, which approaches the optically implied V_OC of ≈795 mV extracted from the luminescence yield of p‐InP.