Larger Triticum aestivum plants do not preempt nutrient-rich patches in a glasshouse experiment

Plant competition belowground generally appears to be size-symmetric, i.e. larger plants only obtain a share of belowground resources proportional to their size, and therefore do not suppress smaller individuals. The experimental evidence for size-symmetric belowground competition comes primarily from experiments with homogenous soil conditions. It has been hypothesized that the presence of high nutrient patches that can be pre-empted by larger plants can make competition belowground size-asymmetric. We tested this hypothesis by growing Triticum aestivum individuals singly and in pairs in containers with aboveground dividers so that competition occurred only belowground. Plants grew in either a homogenous soil mixture, or in the same mixture with a band of enriched soil between them. Initial size differences were generated by a seven day difference in sowing date. There was no evidence of size-asymmetric competition with or without soil heterogeneity. Large plants did not have a disproportionate effect on smaller plants, nor did they perform disproportionately better when paired with a small neighbor. Our results suggest that in heterogeneous soil conditions, roots of larger plants that reach nutrient patches first are not able to prevent roots of smaller plants that arrive later from obtaining resources from the patch. This revised version was published online in August 2006 with corrections to the Cover Date.     

Analysis of relatedness and determination of the source of founders in the captive bearded vulture, Gypaetus barbatus, population

Genetic relatedness among founders is a vitalparameter in the management of captivepopulations as kin structure can have asignificant effect on subsequent populationstructure. Methods for inferring relatednessfrom microsatellite markers have all beendeveloped for natural populations; theirapplicability to captive populations withunknown founder origins needs thereforetesting. We used information derived from 14microsatellites in 177 individuals and Quellerand Goodnight's approach, to estimaterelatedness in the captive bearded vulturepopulation and to test the assumption ofunrelated founders. Mean relatedness of knownparent–offspring, full-sib and half-sib pairswithin the captive population were in agreementwith theoretical distributions. Pairwiserelatedness values among the founders had amean of –0.051 (SE ± 0.007) and theirdistribution did only differ marginally fromthe one found in the natural Pyreneanpopulation. A maximum likelihood approach wasused to determine the likelihood of founderpairs to be as closely related as full-sibs orparent–offspring. These results were combinedwith data from 268 bp mitochondrial DNA controlregion sequences and studbook information. Wecould exclude a close relationship among themajority of the 36 successfully reproducingfounders. Our study therefore removesmanagement concerns about hidden problems ofinbreeding and inbreeding depression. Itdemonstrates the applicability of relatednessestimates based on microsatellite allelefrequency data even in captive populations.Furthermore, we verified studbook informationon the origin of two founders from thePyrenees, and show the value of assignmenttests based on microsatellites for deducingfounder origins and their important role infuture monitoring projects.     

Traits émotionnels, intelligence émotionnelle: intÉrêt de ces concepts et Étude de leurs interrelations

Studies on personality traits conducted during the past decade indicate that there is a set of emotion-related traits on which individuals differ. Moreover, other studies showed that there are some abilities related to the processing of both emotions and emotional information, referred to as the concept of emotional intelligence. The authors of the article evaluated one hundred adults (ranging in age from 20–50) using the French version of a series of scales to measure stable emotionrelated traits and emotional intelligence. The results showed that these instruments provide accurate internal consistency and reliability, and that there are significant relationships between the individual emotional characteristics observed. A factorial analysis conducted with varimax rotation underlined five primary factors identified as: Clear-sightedness of emotions, Emotional richness, Identification, Understanding and Emotional control. The average emotional profiles based on these five primary factors depend on gender and age. In particular, the female and the oldest participants showed a greater emotional richness. The examination of these five factors should lead to a better understanding of the relationships which exist between these emotional characteristics and cognitive performances, and their involvement in clinical syndromes.     

Ecological thresholds and regime shifts: approaches to identification

There is an apparent gap between the prominence of present theoretical frameworks involving ecological thresholds and regime shifts, and the paucity of efforts to conduct simple tests and quantitative inferences on the actual appearance of such phenomena in ecological data. A wide range of statistical methods and analytical techniques are now available that render these questions tractable, some of them even dating back half a century. Yet, their application has been sparse and confined within a narrow subset of cases of ecological regime shifts. Our objective is to raise awareness on the range of techniques available, and to their principles and limitations, to promote a more operational approach to the identification of ecological thresholds and regime shifts.     

Tolerance of switchgrass to extreme soil moisture stress: Ecological implications

Switchgrass (Panicum virgatum L.), a native of eastern and central North America, is a leading candidate as a dedicated biofuel feedstock in the US due to its broad adaptability, rapid growth rate, and ability to grow in low production soils. To begin to characterize the important agronomic and ecological traits related to environmental tolerance of switchgrass, we evaluated fitness under stressful growing conditions. We assessed the germination, establishment, performance, and reproductive potential of four common accessions, both upland and lowland ecotypes, at various levels of soil moisture availability (moisture deficit to flooded) in the greenhouse. Seeds emerged and established (55–90% survival) under all soil moisture conditions (−0.3 MPa to flooded). Transplants of lowland ecotypes performed as well in flooded conditions as in field capacity controls, though flooding reduced performance of upland ecotypes. Drought treatments (−4.0 and −11.0 MPa) reduced tiller length and number, leaf area, and biomass production by up to 80%. However, once established, all plants survived at −4.0 MPa and had the same proportion of tillers in flower as at field capacity. The ability of switchgrass to germinate, establish, and flower in low moisture and flooded conditions, particularly lowland ecotypes, may increase the range of environments suitable for biofuel cultivation, and can serve as a baseline for further ecological studies and genetic improvement.     

黄蜂胃部表皮黄色颗粒的微观形态与发育(英文)

东方大黄蜂（胡蜂）Vespa orientalis（膜翅目Vespinae属）的胃部表皮黄色颗粒位于黄色条纹区域。从黄色颗粒产生至在这一区域扩散,这个过程就是胃部黄颜色形成的过程。用几种电子显微镜研究了黄色颗粒的微观形态和发育过程。结果显示黄色颗粒由20—25 µm厚的一层组成,包括总表皮在内厚度约为40—45 µm。从上面看,在上述的区域能看到许多直径大约为0.5 µm周边光感受器细胞(PPC)。在每个黄色颗粒,能观察到一个肌样包膜,它位于一个由9根原纤维组装而成的圆圈内部。黄色颗粒成熟的过程包含通过导管的渗透增加初生黄色粒子数量,这些初生粒子又发育或增生成次生粒子,次生粒子逐渐布满整个区域。在这些黄色粒子层内可产生类似于肝的功能活动。     

α1-AMP-Activated Protein Kinase Regulates Hypoxia-Induced Na,K-ATPase Endocytosis via Direct Phosphorylation of Protein Kinase Cζ

Hypoxia promotes Na,K-ATPase endocytosis via protein kinase Cζ (PKCζ)-mediated phosphorylation of the Na,K-ATPase α subunit. Here, we report that hypoxia leads to the phosphorylation of 5′-AMP-activated protein kinase (AMPK) at Thr172 in rat alveolar epithelial cells. The overexpression of a dominant-negative AMPK α subunit (AMPK-DN) construct prevented the hypoxia-induced endocytosis of Na,K-ATPase. The overexpression of the reactive oxygen species (ROS) scavenger catalase prevented hypoxia-induced AMPK activation. Moreover, hypoxia failed to activate AMPK in mitochondrion-deficient ρ⁰-A549 cells, suggesting that mitochondrial ROS play an essential role in hypoxia-induced AMPK activation. Hypoxia-induced PKCζ translocation to the plasma membrane and phosphorylation at Thr410 were prevented by the pharmacological inhibition of AMPK or by the overexpression of the AMPK-DN construct. We found that AMPK α phosphorylates PKCζ on residue Thr410 within the PKCζ activation loop. Importantly, the activation of AMPK α was necessary for hypoxia-induced AMPK-PKCζ binding in alveolar epithelial cells. The overexpression of T410A mutant PKCζ prevented hypoxia-induced Na,K-ATPase endocytosis, confirming that PKCζ Thr410 phosphorylation is essential for this process. PKCζ activation by AMPK is isoform specific, as small interfering RNA targeting the α1 but not the α2 catalytic subunit prevented PKCζ activation. Accordingly, we provide the first evidence that hypoxia-generated mitochondrial ROS lead to the activation of the AMPK α1 isoform, which binds and directly phosphorylates PKCζ at Thr410, thereby promoting Na,K-ATPase endocytosis.When exposed to low oxygen levels (hypoxia), cells develop adaptative strategies to maintain adequate levels of ATP (21). These strategies include increasing the efficiency of energy-producing pathways, mostly through anaerobic glycolysis, while decreasing energy-consuming processes such as Na,K-ATPase activity (30). Alveolar hypoxia occurs in many respiratory disorders, and it has been shown to decrease epithelial active Na⁺ transport, leading to impaired fluid reabsorption (37, 41, 42). Active Na⁺ transport and, thus, alveolar fluid reabsortion are effected mostly via apical sodium channels and the basolateral Na,K-ATPase (32, 38, 42). We have reported previously that hypoxia inhibits Na,K-ATPase activity by promoting its endocytosis from the plasma membrane by a mechanism that requires the generation of mitochondrial reactive oxygen species (ROS) and the phosphorylation of the Na,K-ATPase α subunit at Ser18 by protein kinase Cζ (PKCζ) (8, 9).The 5′-AMP-activated protein kinase (AMPK) is a heterotrimeric Ser/Thr kinase composed of a catalytic α subunit and regulatory β and γ subunits. Both isoforms of the AMPK catalytic subunit (α1 and α2) form complexes with noncatalytic subunits. The α1 subunit is ubiquitously expressed, whereas the α2 subunit isoform is expressed predominantly in tissues like the liver, heart, and skeletal muscle (36). The α1 and α2 subunit isoforms have ∼90% homology in their N-terminal catalytic domains and ∼60% homology in their C-terminal domains (36), suggesting that they may have distinct downstream targets (31). AMPK activation requires phosphorylation at Thr172 in the activation loop of the α subunit by upstream kinases (12, 19). Findings from recent studies suggest that AMPK is an important signaling intermediary in coupling ion transport and metabolism (15). Indeed, it has been reported that the pharmacological activation of AMPK inhibits amiloride- and ouabain-sensitive epithelial Na⁺ transport (15). Moreover, the activities of the epithelial Na⁺ channel (ENaC) (2, 17), the Na,K-ATPase (40), and the cystic fibrosis transmembrane conductance regulator (17) have been shown to be inhibited by AMPK. Here, we provide evidence that hypoxia, via mitochondrial ROS, leads to AMPK activation and that AMPK binds to and directly phosphorylates PKCζ in an isoform-specific manner, thus promoting Na,K-ATPase endocytosis in alveolar epithelial cells (AEC).     

Structural understanding of stabilization patterns in engineered bispecific Ig‐like antibody molecules

Bispecific immunoglobulin‐like antibodies capable of engaging multiple antigens represent a promising new class of therapeutic agents. Engineering of these molecules requires optimization of the molecular properties of one of the domain components. Here, we present a detailed crystallographic and computational characterization of the stabilization patterns in the lymphotoxin‐beta receptor (LTβR) binding Fv domain of an anti‐LTβR/anti‐TNF‐related apoptosis inducing ligand receptor‐2 (TRAIL‐R2) bispecific immunoglobulin‐like antibody. We further describe a new hierarchical structure‐guided approach toward engineering of antibody‐like molecules to enhance their thermal and chemical stability. Proteins 2009. © 2009 Wiley‐Liss, Inc.