Manganese phytotoxicity: new light on an old problem

Background Manganese (Mn) is an essential micronutrient that is phytotoxic under certain edaphic and climatic conditions. Multiple edaphic factors regulate Mn redox status and therefore its phytoavailability, and multiple environmental factors including light intensity and temperature interact with Mn phytotoxicity. The complexity of these interactions coupled with substantial genetic variation in Mn tolerance have hampered the recognition of Mn toxcity as an important stress in many natural and agricultural systems.Scope Conflicting theories have been advanced regarding the mechanism of Mn phytotoxicity and tolerance. One line of evidence suggests that Mn toxicity ocurs in the leaf apoplast, while another suggests that toxicity occurs by disruption of photosynthetic electron flow in chloroplasts. These conflicting results may at least in part be attributed to the light regimes employed, with studies conducted under light intensities approximating natural sunlight showing evidence of photo-oxidative stress as a mechanism of toxicity. Excessive Mn competes with the transport and metabolism of other cationic metals, causing a range of induced nutrient deficiencies. Compartmentation, exclusion and detoxification mechanisms may all be involved in tolerance to excess Mn. The strong effects of light, temperature, precipitation and other climate variables on Mn phytoavailability and phytotoxicity suggest that global climate change is likely to exacerbate Mn toxicity in the future, which has largely escaped scientific attention.Conclusions Given that Mn is terrestrially ubiquitous, it is imperative that the heightened risk of Mn toxicity to both managed and natural plant ecosystems be factored into evaluation of the potential impacts of global climate change on vegetation. Large inter- and intraspecific genetic variation in tolerance to Mn toxicity suggests that increased Mn toxicity in natural ecosystems may drive changes in community composition, but that in agroecosystems crops may be developed with greater Mn tolerance. These topics deserve greater research attention.     

Shedding light on the EpCAM: An overview

The epithelial cell adhesion molecule (EpCAM) is a Type I transmembrane superficial glycoprotein antigen that is expressed on the surface of basolateral membrane of multiple epithelial cells with some exceptions such as epidermal keratinocytes, hepatocytes, thymic cortical epithelial cells, squamous stratified epithelial cells, and myoepithelial cells that do not express the molecule. The molecule plays a pivotal role in the structural integrity, adhesion of the epithelial tissues and their interaction with the underlying layers. EpCAM prevents claudin-7 and claudin-1 molecules from degradation, thereby, decreasing the number of tight junctions and cellular interconnections, and promoting the cells toward carcinogenic transformation. Moreover, the mutations in the EpCAM gene lead to congenital tufting enteropathy, severe intestinal epithelium homeostasis disorders, and Lynch and Lynch syndrome. Overexpression of EpCAM on stem cells of some cancers and the presence of this molecule on circulating tumor cells (CTCs) makes it a promising candidate for cancer diagnosis as well as tracing and isolation of CTCs.     

FRET技术在受体信号转导研究中的应用

细胞信号传导是细胞生物学方面的重要内容之一,涉及生命过程的各个方面,包括生长、分化发育、增殖、凋亡、迁移等等,对维持细胞功能及机体生存至关重要。目前对细胞信号转导研究的技术手段多种多样,其中荧光共振能量转移技术（FRET）是研究细胞信号转导较为常用的一种技术,可以实现活细胞内蛋白质之间相互作用的实时检测。本文中我们以受体酪氨酸激酶为例,介绍FRET技术在受体介导细胞信号传导中的应用及进展情况。     

Shedding light on the system: studying embryonic development with light sheet microscopy

Light sheet-based fluorescence microscopy (LSFM) is emerging as a powerful imaging technique for the life sciences. LSFM provides an exceptionally high imaging speed, high signal-to-noise ratio, low level of photo-bleaching and good optical penetration depth. This unique combination of capabilities makes light sheet-based microscopes highly suitable for live imaging applications. There is an outstanding potential in applying this technology to the quantitative study of embryonic development. Here, we provide an overview of the different basic implementations of LSFM, review recent technical advances in the field and highlight applications in the context of embryonic development. We conclude with a discussion of promising future directions.     

Shedding light on a hot topic: Tuberisation in potato

Growing small seedling tubers from true seed, comparable with mini tubers, in controlled conditions could be a method to multiply healthy starting material of potato. In indoor farming systems, the conditions can be optimised for high production. In field trials, it is impossible to investigate the effects of environmental factors such as temperature and light separately. In this study, we performed three climate room experiments in which the effects of light intensity, temperature and percentage of far-red light in the light spectrum on tuber production were assessed. We found that increasing the average temperature reduced tuber number and tuber weight. Increasing the diurnal temperature variation while keeping the average temperature equal resulted in increased tuber size. The light treatments on the other hand only affected the number of tubers per plant: increasing light intensity and increasing the percentage of far-red light in the spectrum enhanced the number of tubers. Moreover, interaction in tuber production between inbred lines and temperature was significant, with some inbred lines being relatively tolerant to high temperature. These findings will help breed for heat tolerant varieties and optimise growing conditions for tuber production in indoor farming systems.     

Shedding light on selenium biomineralization: proteins associated with bionanominerals

Selenium-reducing microorganisms produce elemental selenium nanoparticles with particular physicochemical properties due to an associated organic fraction. This study identified high-affinity proteins associated with such bionanominerals and with nonbiogenic elemental selenium. Proteins with an anticipated functional role in selenium reduction, such as a metalloid reductase, were found to be associated with nanoparticles formed by one selenium respirer, Sulfurospirillum barnesii.     

Shedding light on bioscience. Symposium on Optical Imaging: Applications to Biology and Medicine

This dynamic symposium, held on 11-16 February 2003 in Taos, New Mexico, was the first Keystone meeting to focus on optical techniques and their use in biology and medicine. It was organized by D. Becker, D. Farkas and S. Fraser and attracted almost 100 participants from both academia and industry. Fluorescence imaging and its applications, ranging from nano-bioscience to small-animal imaging and imaging of disease progression in humans, were the main topics, with opportunities for further discussion in the cantinas of the town and on the ski slopes of Taos mountain.     

Anticipation in myotonic dystrophy: new light on an old problem.

The concept of anticipation, the occurrence of a genetic disorder at progressively earlier ages in successive generations, has been debated from the early years of this century, with myotonic dystrophy as the most striking example. Throughout most of this period there has been controversy as to whether the phenomenon resulted from observational and ascertainment biases or reflected a more fundamental mechanism. The recent discovery of inherited unstable DNA sequences, first in fragile-X mental retardation and now in myotonic dystrophy, not only confirms that anticipation indeed has a true biological basis but provides a specific molecular mechanism for it; this discovery can explain many of the puzzling anomalies in the inheritance of myotonic dystrophy and may prove relevant to comparable problems in other genetic disorders.     

Shedding light on shade: ecological perspectives of understorey plant life

Shade, in ecological sense, is not merely a lack of light, but a multi-faceted phenomenon that creates new and complex settings for community and ecosystem dynamics. Tolerating shade therefore affects plants’ ability to cope with other stressors, and also shape its interactions with surrounding organisms. The aim of this broad review was to map our current knowledge about how shade affects plants, plant communities and ecosystems – to gather together knowledge of what we know, but also to point out what we do not yet know. This review covers the following topics: the nature of shade, and ecological and physiological complexities related to growing under a canopy; plants’ capability of tolerating other stress factors while living under a shade – resource trade-offs and polytolerance of abiotic stress; ontogenetic effects of shade tolerance; coexistence patterns under the canopy – how shade determines the forest structure and diversity; shade-induced abiotic dynamics in understorey vegetation, including changing patterns of irradiance, temperature and humidity under the canopy; shade-driven plant–plant and plant–animal interactions – how shade mediates facilitation and stress, and how it creates differentiated environment for different herbivores and pollinators, including the role of volatile organic compounds. We also discuss the ways how vegetation in understorey environments will be affected by climate change, as shade might play a significant role in mitigating negative effects of climate change. Our review shows that living under a shade affects biotic and abiotic stress tolerance of plants, it also influences the outcomes of both symbiotic and competitive plant–plant and plant–animal interactions in a complex and dynamic manner. The current knowledge of shade-related mechanisms is rather ample, however there is much room for progress in integrating different implications of the multifaceted nature of shade into consistent and integral understanding how communities and ecosystems function.     

Shedding light on vampires: the phylogeny of vampyrellid amoebae revisited

With the advent of molecular phylogenetic techniques the polyphyly of naked filose amoebae has been proven. They are interspersed in several supergroups of eukaryotes and most of them already found their place within the tree of life. Although the 'vampire amoebae' have attracted interest since the middle of the 19th century, the phylogenetic position and even the monophyly of this traditional group are still uncertain. In this study clonal co-cultures of eight algivorous vampyrellid amoebae and the respective food algae were established. Culture material was characterized morphologically and a molecular phylogeny was inferred using SSU rDNA sequence comparisons. We found that the limnetic, algivorous vampyrellid amoebae investigated in this study belong to a major clade within the Endomyxa Cavalier-Smith, 2002 (Cercozoa), grouping together with a few soil-dwelling taxa. They split into two robust clades, one containing species of the genus Vampyrella Cienkowski, 1865, the other containing the genus Leptophrys Hertwig & Lesser, 1874, together with terrestrial members. Supported by morphological data these clades are designated as the two families Vampyrellidae Zopf, 1885, and Leptophryidae fam. nov. Furthermore the order Vampyrellida West, 1901 was revised and now corresponds to the major vampyrellid clade within the Endomyxa, comprising the Vampyrellidae and Leptophryidae as well as several environmental sequences. In the light of the presented phylogenetic analyses morphological and ecological aspects, the feeding strategy and nutritional specialization within the vampyrellid amoebae are discussed.     

Early development of the gut: new light on an old hypothesis

This review deals with the early development of the gut. It draws largely on information provided from the study of avian embryos. Evidence that concerns the early determination of the regional fate of the endoderm and mesoderm of the gut is reviewed. Gut endoderm can undergo a limited degree of differentiation from a remarkably early age when cultured in the absence of mesoderm and there is evidence that points to the establishment of a pre-pattern in the early mesoderm before the genes responsible for patterning in gut are active. Initially, at least at cranial levels, those parts of the mesoderm and endoderm that are in contact are not those parts that will ultimately be in apposition; the consequence of this for any signalling between these layers is considered. In the light of the above information, the probable role of mesenchyme in gut development is re-examined.     

Shedding light on sheddases: role in growth and development.

The extracellular domains of several integral membrane proteins are released from the cell surface by a group of enzymes known as "sheddases" through a process called "ectodomain shedding". Because many transmembrane growth and differentiation factors, including members of the epidermal growth factor (EGF) family that play a crucial role in development, require ectodomain shedding for proper action in vivo, proteolysis is now viewed as a regulatory mechanism in the developing embryos. Two recent reports by Zhao et al. provide evidence for the role of cell surface proteolysis by an ADAM (a disintegrin and metalloprotease) in the development of murine lung. Inhibition of tumor necrosis factor-alpha converting enzyme (TACE, ADAM17) by the hydroxamic acid-based metalloprotease inhibitor (TAPI), or a targeted mutation in Zn(2+)-binding domain of TACE, disrupts two essential epithelial functions in lung development: branching morphogenesis and cytodifferentiation. Evidence for the role of ADAMs as sheddases in development and growth factor signaling is discussed.     

Shedding light on moths: shorter wavelengths attract noctuids more than geometrids

With moth declines reported across Europe, and parallel changes in the amount and spectra of street lighting, it is important to understand exactly how artificial lights affect moth populations. We therefore compared the relative attractiveness of shorter wavelength (SW) and longer wavelength (LW) lighting to macromoths. SW light attracted significantly more individuals and species of moth, either when used alone or in competition with LW lighting. We also found striking differences in the relative attractiveness of different wavelengths to different moth groups. SW lighting attracted significantly more Noctuidae than LW, whereas both wavelengths were equally attractive to Geometridae. Understanding the extent to which different groups of moth are attracted to different wavelengths of light will be useful in determining the impact of artificial light on moth populations.