Multiple ligand-binding properties of the lipocalin member chicken α1-acid glycoprotein studied by circular dichroism and electronic absorption spectroscopy: The essential role of the conserved tryptophan residue

Multiple ligand-binding properties of the 30-kDa chicken α₁-acid glycoprotein (cAGP), a member of the lipocalin protein family, were investigated for the first time by using circular dichroism (CD) and UV/Vis absorption spectroscopy methods. By measuring induced CD (ICD) spectra, high-affinity binding (K_a ≈ 10⁵–10⁶ M⁻¹) of several drugs, dyes and natural compounds to cAGP was demonstrated including antimalarial agents (quinacrine, primaquine), phenotiazines (chlorpromazine, methylene blue), propranolol, non-steroidal antiinflammatory drugs (ketoprofen, diclofenac), tamoxifen, diazepam, tacrine, dicoumarol, cationic dyes (auramine O, thioflavine T, ethidium bromide), benzo[a]pyrene, l-thyroxine, bile pigments (bilirubin, biliverdin), alkaloids (piperine, aristolochic acid), saturated and unsaturated fatty acids. Analysis of the extrinsic CD spectra with the study of the covalently modified protein and CD displacement experiments revealed that a single Trp26 residue of cAGP conserved in the whole lipocalin family is part of the binding site, and it is essentially involved in the ligand-binding process via π–π stacking interaction resulting in the appearance of strong induced CD bands due to the non-degenerate intermolecular exciton coupling between the π–π* transitions of the stacked indole ring–ligand chromophore. The finding that cAGP is able to accommodate a broad spectrum of ligands belonging to different chemical classes suggests that its core β-barrel cavity is unusually wide containing overlapping sub-sites. Significance of these new data in understanding of the ligand-binding properties of other lipocalins, especially that of human AGP, and potential practical applications are briefly discussed. Overall, cAGP serves as a simple, ultimate model to extend our knowledge on ligand-binding properties of lipocalins and to study the role of tryptophan residues in molecular recognition processes.     

Annual Medicago: from a model crop challenged by a spectrum of necrotrophic pathogens to a model plant to explore the nature of disease resistance

BACKGROUND: Annual Medicago spp., including M. truncatula, play an important agronomic role in dryland farming regions of the world where they are often an integral component of cropping systems, particularly in regions with a Mediterranean or Mediterranean-type climate where they grow as winter annuals that provide both nitrogen and disease breaks for rotational crops. Necrotrophic foliar and soil-borne pathogens dominate these regions and challenge the productivity of annual Medicago and crop legume species. SCOPE: This review outlines some of the major and/or widespread diseases these necrotrophic pathogens cause on Medicago spp. It then explores the potential for using the spectrum of necrotrophic pathogen-host interactions, with annual Medicago as the host plant, to better understand and model pathosystems within the diseases caused by nectrotrophic pathogens across forage and grain legume crops. CONCLUSIONS: Host resistance clearly offers the best strategy for cost-effective, long-term control of necrotrophic foliar and soil-borne pathogens, particularly as useful resistance to a number of these diseases has been identified. Recently and initially, the annual M. truncatula has emerged as a more appropriate and agronomically relevant substitute to Arabidopsis thaliana as a model plant for legumes, and is proving an excellent model to understand the mechanisms of resistance both to individual pathogens and more generally to most forage and grain legume necrotrophic pathogens.     

不同硬度类型小麦高分子量谷蛋白亚基组成及遗传多样性分析

为了在小麦品质育种中充分利用品种资源,以引进的57份小麦品种(系)为试验材料,采用SDS-PAGE和单籽粒硬度仪(SKCS)分析了这些品种(系)的高分子量谷蛋白亚基(HMW-G S)组成及其籽粒硬度.共检测到13种亚基和21种亚基组合,30份材料具有5 10亚基,10份2*,9份17 18,1份13 16.5 10和2*在硬质麦中出现的频率较混合麦高,在软质麦中的频率最低,17 18在混合麦中的频率较高.HMW-G S组合中,N u ll、7 9、2 12和1、7 8、2 12的频率较高,分别为17.5%和14.0%,个别品种还同时聚合有1A、1B、1D上的优质亚基.参试品种(系)含硬质麦32份(1级20份、2级12份),混合麦15份(2级3份,3级12份),软质麦10份(4级6份,5级4份),籽粒硬度的分布范围为12~74.春小麦和冬小麦材料N e i s平均遗传变异系数分别为0.550 8和0.573 3,表明春小麦的高分子量谷蛋白位点的遗传变异略低于冬小麦;春小麦和冬小麦A、B和D基因组的N e i s平均遗传变异系数分别为0.497 5、0.648 7和0.540 3,说明G lu-B 1位点的遗传多样性最高,其次是G lu-D 1位点,G lu-A 1位点最低.     

Somatic embryogenesis and plant regeneration from cotyledonary explants of green gram [Vigna radiata (L.) Wilezek.]—A recalcitrant grain legume

Summary This study reports a protocol for plant regeneration from cultured explants of green gram [Vigna radiata (L.) Wilezek] via somatic embryogenesis. Somatic embryos were induced from nature cotyledons of var., TAP-7 and Pusa Baisaki when cultured on Murashige and Skoog (MS) medium fortified with different concentrations of 2,4-dichlorophenoxyacetic acid, α-naphthaleneacetic acid (NAA) and 2,4,5-trichlorophenoxyacetic acid singly or in combination with 2.22–8.88 μM N ⁶-benzylaminopurine (BAP) or 2.32–9.38 μM kinetin. The type and concentration of auxin and plant genotype influenced the frequency of somatic embryogenesis. NAA was the most effective auxin for somatic embryo induction. The well-developed, cotyledonary shaped embryos of var. TAP-7 germinated into plantlets at a frequency of 56.6% on MS medium supplemented with 1.88 μM abscisic acid and 6.66 μM BAP. Regenerated plants were transferred to soil and grown to maturity with 90% survival. The protocol described here offers a good potential for genetic improvement using gene transfer techniques and the production of synthetic seeds of V. radiata.     

Phenotypic plasticity in two marine snails: constraints superseding life history

In organisms encountering predictable environments, fixed development is expected, whereas in organisms that cannot predict their future environment, phenotypic plasticity would be optimal to increase local adaptation. To test this prediction we experimentally compared phenotypic plasticity in two rocky-shore snail species; Littorina saxatilis releasing miniature snails on the shore, and Littorina littorea releasing drifting larvae settling on various shores, expecting L. littorea to show more phenotypic plasticity than L. saxatilis. We compared magnitude and direction of vectors of phenotypic difference in juvenile shell traits after 3 months exposure to different stimuli simulating sheltered and crab-rich shores, or wave-exposed and crab-free shores. Both species showed similar direction and magnitude of vectors of phenotypic difference with minor differences only between ecotypes of the nondispersing species, indicating that plasticity is an evolving trait in L. saxatilis. The lack of a strong plastic response in L. littorea might be explained by limits rather than costs to plasticity.     

A comparison of ring-width and event-year chronologies derived from white oak (Quercus alba) and northern red oak (Quercus rubra), southwestern Quebec, Canada

In dendrochronology, ring width has been a variable of choice when assessing the radial growth–climate association of tree species. We compared ring-width and event-year chronologies from a dendroclimatic perspective using both white oak (Quercus alba L.) and northern red oak (Quercus rubra L.). The study was conducted in three regions of the Ottawa valley in southern Québec. Twelve mixed red and white oak stands were selected and for each oak species, 12 chronologies were developed from tree-ring measurement and 12 others were derived using visual assessment of narrow or wide rings (event years). Ring-width and event-year chronologies gave almost identical results and revealed the prevalence of drought in the early growing season as the most influential factor in both species. This study emphasizes the utility of event-year chronologies in tree-ring studies and their comparativeness with ring width. Establishing event-year chronologies has the advantage of being faster than measuring ring width, it does not necessitate complex equipment and depending on the purpose of the study may prove to be at least comparable. The choice of species, their mean sensitivity, the ability to recognize narrow or large rings as well as the number of trees and sites to analyze may, however, be factors to consider when choosing to use event-year chronologies over the more commonly used ring-width ones.     

水稻磷效率相关性状的遗传特性

利用数量遗传模型对P1、P2、F1、F2．3等4个世代的相对分蘖率、有效穗、生物产量及经济产量等性状进行了遗传分析。混合遗传模型分析表明：低磷胁迫条件下,相对分蘖率和相对有效穗两个指标适合两对主基因的加性．显性．上位性的模型,两对主基因之间存在着广泛的加性、显性和上位性效应,也存在多基因修饰;相对分蘖率和相对有效穗的最大效应主基因以加性效应为主,次大主基因以显性效应为主,而相对生物量与相对经济产量两个指标符合两对加性．显性．上位性主基因＋多基因的模型,主基因遗传力分别达到60．08％和37．70％,多基因遗传力分别达到32．15％和58．9％。表明相对分蘖率、有效穗和生物量的主基因遗传力均较高,可以作为水稻耐低磷遗传育种的指标。而相对经济产量的主基因遗传力相对较低,说明经济产量受气候等环境因素影响较大。     

沈阳市区古油松年轮宽度年表的建立

以沈阳城区昭陵古油松为样本,建立了古油松标准化年表、差值年表和自回归年表．结果表明,年表与沈阳1月和4月的极端最低气温显著相关;与2月的降水量、年均水汽压分别为显著和极显著相关,年表对4、5、9和10月的水汽压响应较强,且均与自回归年表显著相关．年表与相对湿度的年指标,4、5、6、9、10和11月月指标的相关性较高,其中与年值和5月值分别为显著相关（差值年表除外）和极显著相关．蒸发与油松的生长在全年和绝大部分月份呈负相关,其中5月最明显,而1月的蒸发量与油松年表呈正相关．年表的窄化突变佐证了1700年以来32次历史资料记录的主要旱灾年．沈阳地区的油松生长也受全球或半球尺度温度波动的影响．3种年表对以往太阳黑子的变化和地磁的活动呈现明显负相关,其中与太阳黑子活动存在显著的11年、23年和50年左右的公共周期,与地磁指标在10．5年、20年和45年左右存在共同的周期变化．     

Differential levels of mite infestation of wheat and barley in Czech grain stores

Abstract  While mites are able to utilize numerous food sources, the suitability of the food strongly influences population growth. The different suitabilities of various stored agricultural products will thus affect the level of infestation. In this study, we compared field mite infestation rates in two stored cereals: wheat and barley. We analyzed mite abundance, frequency and species composition in samples of grain obtained from 79 selected Czech grain stores. Stored barley seemed to be more vulnerable to mite attack than wheat, as we consistently found more infested samples, more species and higher mean and median mite abundance per sample in barley as compared to wheat. The mean mite abundance per sample were 55 and 506 individuals for wheat and barley, respectively. In barley, 10% of samples exceeded allergen risk threshold (i.e., 1 000 individuals per kg of grain). Altogether, 25 species were identified from approximately 35 000 individuals. The most frequently identified species were the same in wheat and barley, that is, Tydeus interruptus Sig Thor, Acarus siro L., Tarsonemus granarius Lindquist, Lepidoglyphus destructor (Schrank) and Tyrophagus putrescentiae (Schrank). Based on principal components analysis, we found a closer association of T. interruptus , T. putrescentiae , L. destructor and Cheyletus eruditus (Schrank) with barley samples, corresponding to the high frequency and abundance values of these mites. The probable reasons for the higher infestation, especially mite abundance in barley, are discussed in relation to the higher proportion of crushed parts, which may release favorable nutrient sources and amplify the abundance values.     

Structural and electrostatic characterization of Pariacoto virus: Implications for viral assembly

We present the first all‐atom model for the structure of a T = 3 virus, pariacoto virus (PaV), which is a nonenveloped, icosahedral RNA virus and a member of the Nodaviridae family. The model is an extension of the crystal structure, which reveals about 88% of the protein structure but only about 35% of the RNA structure. New modeling methods, combining coarse‐grained and all‐atom approaches, were required for developing the model. Evaluation of alternative models confirms our earlier observation that the polycationic N‐ and C‐terminal tails of the capsid proteins must penetrate deeply into the core of the virus, where they stabilize the structure by neutralizing a substantial fraction of the RNA charge. This leads us to propose a model for the assembly of small icosahedral RNA viruses: nonspecific binding of the protein tails to the RNA leads to a collapse of the complex, in a fashion reminiscent of DNA condensation. The globular protein domains are excluded from the condensed phase but are tethered to it, so they accumulate in a shell around the condensed phase, where their concentration is high enough to trigger oligomerization and formation of the mature virus. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 530–538, 2009. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com