Diazotrophic endophytes: progress and prospects for nitrogen fixation in monocots

Spatial variability of plant growth has been a major problem for plant physiologists, agronomists, agro-foresters and soil scientists comparing or modelling treatment effects on acid sandy soils in the Sahel. While aerial photographs from aeroplanes or satellite images may provide valuable information for the surveying of large areas, their use for individual small experiments or farmers' fields has been limited due to high costs, restricted availability, and unsatisfactory resolution. As a simple alternative, a commercially available Zeppelin-type balloon, dragged on a rope by a camel, was fitted with an standard 35 mm camera and a remote control system. Flight altitude varied from 20 m to 500 m above ground. A ground-based camera mounted vertically on a tripod was used to center the Zeppelin over the target area. The high-resolution true colour negatives and colour infrared slides obtained by this device were used to unravel the history of farmers' management strategies for maintaining soil productivity, to monitor treatment effects and crop growth variability in an on-station experiment, and to visualize light absorption by photosynthesis in crops and trees. Such non-destructively collected data may serve as quick but reliable references for ground measurements in a wide range of experiments with loosely-spaced crops, bushes, and trees. ei]B E Clothier     

Contracting Tasmanian montane grasslands within a forest matrix is consistent with cessation of Aboriginal fire management

The persistence of treeless grasslands and sedgelands within a matrix of eucalypt and rainforest vegetation in the montane plateaux of northern Tasmania has long puzzled ecologists. Historical sources suggest that Tasmanian Aborigines were burning these treeless patches and models seeking to explain their maintenance generally include fire, soil properties and Aboriginal landscape burning. We aimed to provide a new historical perspective of the dynamics of the vegetation mosaics of Surrey Hills and Paradise Plains in north‐west and north‐east Tasmania, respectively, and used vegetation surveys and soil sampling to explore the role of vegetation and soils in these dynamics. Sequences of historical maps (1832 and 1903) and aerial photography showed that many treeless patches have persisted in the landscape since European settlement and that forests have rapidly expanded into the treeless patches since the early 1950s. Stand structure and floristic data described an expanding forest dominated by Leptospermum, which is consistent with vegetation succession models for the region. Soils under expanding forest boundaries did not have higher soil nitrogen or phosphorus than those under stable boundaries, signalling a lack of edaphic limitation to forest expansion. The magnitude of forest expansion at Paradise Plains (granite), Surrey Hills (basalt) and south‐west Tasmania (quartzite) appears to follow a nutrient availability gradient and this hypothesis is backed by differences in soil phosphorus capital between the three systems. Given that existing vegetation boundaries in northern Tasmania do not coincide with soil nutrient gradients, we suggest that treeless vegetation was maintained by Aboriginal landscape burning and that the recent contraction of treeless vegetation is related to the breakdown of these fire regimes following European settlement. The observed rates of forest expansion could result in a substantial loss of these grasslands if sustained through this century and therefore our work supports the continuation of prescribed burning to maintain this high conservation value ecosystem.     

尿液分析及胸部X线筛查重度感染或者脓毒性休克感染源的回顾性分析

目的：评估重症监护室的重症感染或者脓毒性休克患者尿常规检查和胸部X线检查的准确性。方法：回顾性分析我院进入重症监护室的确诊为重症感染或者脓毒性休克的患者,收集所有入组患者的个人情况,进入监护室以后的尿液检查结果、胸部X线检查结果,以及体液细菌学培养的结果,分析上述数据与诊断泌尿系感染或者肺部感染之间关系。结果：我们回顾了400例患者,其中70例患者确诊为重症感染或者脓毒性休克,其中13例患者确诊为泌尿系感染（尿常规,白细胞〉10／高倍镜视野）,敏感性和特异性分别为81％（95％CI0．67-0．92）和65％（95％CI0．51—0．75）;36例患者确诊为肺部感染,胸部X线检查诊断肺部感染的的敏感性和特畀性分别为57％（95％C10．45—0．69）和92％（95％C10．82-0．93）。结论：对于脓毒血症或者脓毒性休克的患者,胸部X线检查敏感性较低,这可能与肺部X线检查干扰因素较多,并且肺部感染发生到出现影像学变化有一定的时间间隔：而尿液分析敏感性较高,但是也可能由于尿液中上皮细胞的存在而干扰诊断。     

小兴安岭白桦次生林叶面积指数的估测

叶面积指数(LAI)是量化冠层结构最常用的参数之一,准确估测LAI对森林生态系统结构特性的研究具有重要意义.利用半球摄影图像法和LAI-2000法及半球摄影图像法结合凋落物法估测了小兴安岭白桦次生林LAI及其动态变化.首先对该林型叶凋落末期(11月初)的半球摄影图像进行合理校正(包括木质部分所占比例α,冠层水平集聚指数ΩE,校正值作为该时期常绿树种的真实LAI(LAIt),结合各调查期的凋落物数据,得到落叶季节(7-11月)的LAIt,并以该值为参考值,对比分析了两种光学仪器法估测值.结果表明:两种光学仪器法在LAI最大时期低估(分别低估2.83％、6.20％),其他时期显著高估(平均高估118.13％、89.34％),但两种光学仪器法与探讨方法估测值存在很好的相关性:LAIt=-1.1393+1.0934·LAIHP,R2=0.80; LAIt=-0.1712+0.6259·LAILAI-2000,R2=0.83.研究结果可为将来方便、快捷、准确的估测白桦次生林的LAI提供参考.     

Background matching,disruptive coloration,and differential use of microhabitats in two neotropical grasshoppers with sexual dichromatism

Cryptic coloration is an adaptative defensive mechanism against predators. Color patterns can become cryptic through background coloration‐matching and disruptive coloration. Disruptive coloration may evolve in visually heterogeneous microhabitats, whereas background matching could be favored in chromatically homogeneous microhabitats. In this work, we used digital photography to explore the potential use of disruptive coloration and background matching in males and females of two grasshopper species of the Sphenarium genus in different habitats. We found chromatic differences in the two grasshopper species that may be explained by local adaptation. We also found that the females and males of both species are dichromatic and seem to follow different color cryptic strategies, males are more disruptive than females, whereas females have a high background matching with less disruptive elements. The selective pressures of the predators in different microhabitats and the differences in mobility between sexes may explain the color pattern divergence between females and males. Nevertheless, more field experiments are needed in order to understand the relative importance of disruptive and background matching coloration in the evolution of sexual dichromatism in these grasshoppers.     

Response of rigor cross-bridges to stretch detected by fluorescence lifetime imaging microscopy of myosin essential light chain in skeletal muscle fibers

We applied fluorescence lifetime imaging microscopy to map the microenvironment of the myosin essential light chain (ELC) in permeabilized skeletal muscle fibers. Four ELC mutants containing a single cysteine residue at different positions in the C-terminal half of the protein (ELC-127, ELC-142, ELC-160, and ELC-180) were generated by site-directed mutagenesis, labeled with 7-diethylamino-3-((((2-iodoacetamido)ethyl)amino)carbonyl)coumarin, and introduced into permeabilized rabbit psoas fibers. Binding to the myosin heavy chain was associated with a large conformational change in the ELC. When the fibers were moved from relaxation to rigor, the fluorescence lifetime increased for all label positions. However, when 1% stretch was applied to the rigor fibers, the lifetime decreased for ELC-127 and ELC-180 but did not change for ELC-142 and ELC-160. The differential change of fluorescence lifetime demonstrates the shift in position of the C-terminal domain of ELC with respect to the heavy chain and reveals specific locations in the lever arm region sensitive to the mechanical strain propagating from the actin-binding site to the lever arm.     

Ancient ubiquitous protein 1 (AUP1) localizes to lipid droplets and binds the E2 ubiquitin conjugase G2 (Ube2g2) via its G2 binding region

Lipid droplets (LDs), the major intracellular storage sites for neutral lipids, consist of a neutral lipid core surrounded by a phospholipid monolayer membrane. In addition to their function in lipid storage, LDs participate in lipid biosynthesis and recently were implicated in proteasomal protein degradation and autophagy. To identify components of the protein degradation machinery on LDs, we studied several candidates identified in previous LD proteome analyses. Here, we demonstrate that the highly conserved and broadly expressed ancient ubiquitous protein 1 (AUP1) localizes to LDs, where it integrates into the LD surface in a monotopic fashion with both termini facing the cytosol. AUP1 contains a C-terminal domain with strong homology to a domain known as G2BR, which binds E2 ubiquitin conjugases. We show that AUP1, by means of its G2BR domain, binds to Ube2g2. This binding is abolished by deletion or mutation of the G2BR domain, although the LD localization of AUP1 is not affected. The presence of the AUP1-Ube2g2 complex at LDs provides a direct molecular link between LDs and the cellular ubiquitination machinery.     

The protease-activated receptor-2-specific agonists 2-aminothiazol-4-yl-LIGRL-NH2 and 6-aminonicotinyl-LIGRL-NH2 stimulate multiple signaling pathways to induce physiological responses in vitro and in vivo

Protease-activated receptor-2 (PAR₂) is one of four protease-activated G-protein-coupled receptors. PAR₂ is expressed on multiple cell types where it contributes to cellular responses to endogenous and exogenous proteases. Proteolytic cleavage of PAR₂ reveals a tethered ligand that activates PAR₂ and two major downstream signaling pathways: mitogen-activated protein kinase (MAPK) and intracellular Ca²⁺ signaling. Peptides or peptidomimetics can mimic binding of the tethered ligand to stimulate signaling without the nonspecific effects of proteases. The most commonly used peptide activators of PAR₂ (e.g. SLIGRL-NH₂ and SLIGKV-NH₂) lack potency at the receptor. However, although the potency of 2-furoyl-LIGRLO-NH₂ (2-f-LIGRLO-NH₂) underscores the use of peptidomimetic PAR₂ ligands as a mechanism to enhance pharmacological action at PAR₂, 2-f-LIGRLO-NH₂ has not been thoroughly evaluated. We evaluated the known agonist 2-f-LIGRLO-NH₂ and two recently described pentapeptidomimetic PAR₂-specific agonists, 2-aminothiazol-4-yl-LIGRL-NH₂ (2-at-LIGRL-NH₂) and 6-aminonicotinyl-LIGRL-NH₂ (6-an-LIGRL-NH₂). All peptidomimetic agonists stimulated PAR₂-dependent in vitro physiological responses, MAPK signaling, and Ca²⁺ signaling with an overall rank order of potency of 2-f-LIGRLO-NH₂ ≈ 2-at-LIGRL-NH₂ > 6-an-LIGRL-NH₂ ≫ SLIGRL-NH₂. Because PAR₂ plays a major role in pathological pain conditions and to test potency of the peptidomimetic agonists in vivo, we evaluated these agonists in models relevant to nociception. All three agonists activated Ca²⁺ signaling in nociceptors in vitro, and both 2-at-LIGRL-NH₂ and 2-f-LIGRLO-NH₂ stimulated PAR₂-dependent thermal hyperalgesia in vivo. We have characterized three high potency ligands that can be used to explore the physiological role of PAR₂ in a variety of systems and pathologies.     

Natural and anthropogenic changes to mangrove distributions in the Pioneer River Estuary (QLD,Australia)

We analyzed a time series of aerial photographs and Landsat satellite imagery of the Pioneer River Estuary (near Mackay, Queensland, Australia) to document both natural and anthropogenic changes in the area of mangroves available to filter river runoff between 1948 and 2002. Over 54 years, there was a net loss of 137 ha (22%) of tidal mangroves during four successive periods that were characterized by different driving mechanisms: (1) little net change (1948–1962); (2) net gain from rapid mangrove expansion (1962–1972); (3) net loss from clearing and tidal isolation (1972–1991); and (4) net loss from a severe species-specific dieback affecting over 50% of remaining mangrove cover (1991–2002). Manual digitization of aerial photographs was accurate for mapping changes in the boundaries of mangrove distributions, but this technique underestimated the total loss due to dieback. Regions of mangrove dieback were identified and mapped more accurately and efficiently after applying the Normalized Difference Vegetation Index (NDVI) to Landsat Thematic Mapper satellite imagery, and then monitoring changes to the index over time. These remote sensing techniques to map and monitor mangrove changes are important for identifying habitat degradation, both spatially and temporally, in order to prioritize restoration for management of estuarine and adjacent marine ecosystems.     

Changes in sexual signals are greater than changes in ecological traits in a dichromatic group of fishes

Understanding the mechanisms by which phenotypic divergence occurs is central to speciation research. These mechanisms can be revealed by measuring differences in traits that are subject to different selection pressures; greater influence of different types of selection can be inferred from greater divergence in associated traits. Here, we address the potential roles of natural and sexual selection in promoting phenotypic divergence between species of snubnose darters by comparing differences in body shape, an ecologically relevant trait, and male color, a sexual signal. Body shape was measured using geometric morphometrics, and male color was measured using digital photography and visual system‐dependent color values. Differences in male color are larger than differences in body shape across eight allopatric, phylogenetically independent species pairs. While this does not exclude the action of divergent natural selection, our results suggest a relatively more important role for sexual selection in promoting recent divergence in darters. Variation in the relative differences between male color and body shape across species pairs reflects the continuous nature of speciation mechanisms, ranging from ecological speciation to speciation by sexual selection alone.