Polymorphism and physiology of arsenate tolerance in Holcus lanatus L. from an uncontaminated site

The polymorphism of arsenate tolerance in a Holcus lanatus L. population from an uncontaminated soil was investigated and a high percentage of tolerant individuals (65%) was found in the population studied. Influx of arsenate was highly correlated to arsenate tolerance within the population, with the most tolerant individuals having the lowest rates of arsenate influx. Isotherms for the high affinity arsenate uptake systems were determined in six tolerant and six non-tolerant genotypes. Tolerant plants had the lowest rates of arsenate influx. This was achieved by adaptation of the V_max of arsenate influx with the V_max of the high affinity uptake system saturating at lower substrate concentrations in the tolerant plants. The polymorphism is discussed with relation to adaptation to the extreme environments to which the plants are subjected on mine-spoil soils.     

Effects of phosphate on arsenate and arsenite sensitivity in two rice (Oryza sativa L.) cultivars of different sensitivity

Arsenate and arsenite sensitivity and arsenate influx tests were conducted for two rice cultivars of different arsenic sensitivity, Azucena and Bala. These were to establish if the mechanism of reduced arsenic sensitivity is achieved through an altered phosphate uptake system, as shown for Holcus lanatus. High phosphate treatments (≥50 μM) provided protection against both arsenate and arsenite. Unlike the H. lanatus tolerance mechanism, in the less sensitive cultivar Bala, arsenate influx did not decrease with phosphate treatment and phosphate transporters appeared to be constitutively upregulated; V_max for arsenate influx remain similar when Bala was grown in the presence or absence of phosphate (V_max - 0.90 and 0.63 nmol g⁻¹ f.wt min⁻¹ respectively). Although mean K_m appear different, Bala did not show lower affinity to arsenate than Azucena in the absence of phosphate (K_m - Azucena, 0.30 mM and Bala, 0.18), while in phosphate treatment, Bala arsenate affinity was half that observed for Azucena (K_m - Azucena, 0.14 and Bala, 0.36 mM). These were low compared to a 4 and 6 fold decrease seen for similar studies on H. lanatus in the absence and presence of phosphate. Phosphate-induced arsenic protection was observed but the mechanism does not resemble that of H. lanatus. Alternative mechanisms were discussed.     

Expression of five frizzleds during zebrafish craniofacial development

Wnt/Planar Cell Polarity (PCP) signaling is critical for proper animal development. While initially identified in Drosophila, this pathway is also essential for the proper development of vertebrates. Zebrafish mutants, defective in the Wnt/PCP pathway, frequently display defects in convergence and extension gastrulation movements and additional later abnormalities including problems with craniofacial cartilage morphogenesis. Although multiple Frizzled (Fzd) homologues, Wnt receptors, were identified in zebrafish, it is unknown which Fzd plays a role in shaping the early larvae head skeleton. In an effort to determine which Frizzleds are involved in this process, we analyzed the expression of five zebrafish frizzled homologues fzd2, 6, 7a, 7b, and 8a from 2–4 days post-fertilization (dpf). During the analyzed developmental time points fzd2 and fzd6 are broadly expressed throughout the head, while the expression of fzd7a, 7b and 8a is much more restricted. Closer examination revealed that fzd7b is expressed in the neural crest and the mesodermal core of the pharyngeal arches and in the chondrocytes of newly stacked craniofacial cartilage elements. However, fzd7a is only expressed in the neural crest of the pharyngeal arches and fzd8a is expressed in the pharyngeal endoderm.     

鄱阳湖洲滩湿地植物生长和营养繁殖对水淹时长的响应

水淹时长是影响湿地植物分布的重要因素。在水情不断变化的背景下,鄱阳湖洲滩湿地植物种群和群落的变化规律还不清楚。为了探究淹水时长对鄱阳湖洲滩3种优势植物生长和繁殖的影响,并预测在水文发生剧烈变化后,3种优势植物分布的趋势,采用控制实验模拟了不同水淹时长(0、60、90、120、150 d和180 d)下鄱阳湖湿地3种优势植物(灰化薹草(Carex cinerascens)、南荻(Miscanthus lutarioriparius)和虉草(Phalaris arundinacea))的生长和繁殖情况。研究结果表明:1)南荻在水淹超过120 d后,存活率开始降低,水淹到达180 d完全死亡。而灰化薹草和虉草在淹水180 d后仍全部存活。表明南荻耐淹水的能力弱于其他两种植物。2)水淹显著降低灰化薹草的总生物量,并且总生物量随水淹时长的增加而逐渐降低。而短时间(小于150 d)的水淹没有对虉草总生物量产生显著影响。3)退水初期,灰化薹草的恢复生长趋向于地上部分,而虉草表现为地下和地下部分同步生长。该研究结果可以为预测水文情势变化下鄱阳湖湿地植物种群和群落的动态变化提供依据。     

不同水淹深度对鄱阳湖洲滩湿地植物生长及营养繁殖的影响

水淹深度是影响湿地植物生长和繁殖的关键因子,不同湿地植物对淹水深度存在着不同响应。然而,在水情不断变化的背景下,鄱阳湖洲滩湿地植物种群和群落如何变化还不清楚。为了探究淹水深度对湿地植物生长的影响,并预测鄱阳湖洲滩湿地植被分布的趋势,采用控制实验模拟了不同水淹深度(0、0.5、1 m和2 m)下鄱阳湖湿地3种优势植物(灰化薹草(Carex cinerascens)、南荻(Miscanthus lutarioriparius)和虉草(Phalaris arundinacea))的生长和繁殖情况。实验结果表明:1)水淹对灰化薹草总生物量的影响最显著。遭受水淹时,灰化薹草把大部分的生物量集中在地下部分;随着水淹深度逐渐增加,南荻的生物量逐渐减少;不同深度水淹对虉草生物量没有产生显著影响(P0.05)。就生物量而言,虉草对水淹的适应性强于其他两种植物。2)不同水淹深度下,灰化薹草的株高都显著降低;而南荻只在2 m水淹梯度下株高才显著降低。在枯水年时,下降的水位有利于南荻向较低高程迁移。3)不同深度水淹对灰化薹草的分株没有产生显著影响(P0.05);而虉草在经过2 m水淹后分株数显著高于其他水淹深度。在丰水年时,相比于灰化薹草和南荻,升高的水位对虉草的繁殖影响较小。在一个水位周期性变化的湿地生态系统中,不同深度的水淹对植物的生长及退水后的繁殖产生了严重影响,研究结果为预测水文变化对湿地植被的生存和分布提供了重要的依据。     

A comparison of N and C uptake during brown tide (Aureococcus anophagefferens) blooms from two coastal bays on the east coast of the USA

Blooms of the brown tide pelagophyte, Aureococcus anophagefferens, have been reported in coastal bays along the east coast of the USA for nearly two decades. Blooms appear to be constrained to shallow bays that have low flushing rates, little riverine input and high salinities (e.g., >28). Nutrient enrichment and coastal eutrophication has been most frequently implicated as the cause of A. anophagefferens and other blooms in coastal bays. We compare N and C dynamics during two brown tide blooms, one in Quantuck Bay, on Long Island, NY in 2000, and the other in Chincoteague Bay, at Public Landing, MD in 2002, with a physically similar site in Chincoteague Bay that did not experience a bloom. We found that the primary forms of nitrogen (N) taken up during the bloom in Quantuck Bay were ammonium and dissolved free amino acids (DFAA) while the primary form of N fueling production at both sites in Chincoteague Bay was urea. At both Chincoteague sites, amino acid carbon (C) was taken up while urea C was not. Even though A. anophagefferens has the ability to take up organic C, during the bloom at Chincoteague Bay, photosynthetic uptake of bicarbonate was the dominant pathway of C acquisition by the >1.2 μm size fraction during the day. C uptake by cells <5.0 μm was insufficient to meet cellular C demand based on the measured N uptake rates and the C:N ratio of particulate material. While cells >1.2 μm did not take up much organic C during the day, smaller cells (>0.2 μm) did. Peptide hydrolysis appeared to play an important role in mobilizing organic matter in Quantuck Bay, where amino acids contributed substantially to N and C uptake, but not in Chincoteague Bay. Dissolved organic N (DON), dissolved organic C (DOC) concentrations and the DOC/DON ratio were higher and total dissolved inorganic N (DIN) concentrations were lower at the bloom site in Chincoteague Bay than at the nonbloom site in the same bay. We conclude that A. anophagefferens is capable of using a wide variety of N and C compounds, and that nutrient inputs, biotic interactions and the dominant recycling pathways determine which compounds are available and which metabolic pathways are active at a particular site.     

Erwinia soft rot resistance of potato cultivars expressing antimicrobial peptide tachyplesin I

Tachyplesin I is a 2.3 kDa antimicrobial peptide isolated from Southeast Asian horseshoe crabs. Bacterial suspensions containing 1×10⁶ colony-forming units/ml of six isolates of pectolytic Erwinia spp., the causal pathogens of potato soft rot and blackleg, were killed in vitro by 1.4 to 11.1 g/ml of tachyplesin I. In an attempt to enhance resistance to Erwinia spp., each of the potato cultivars Bintje, Karnico and Kondor were transformed with two gene constructs encoding different precursor tachyplesin I proteins under the control of a cauliflower mosaic virus 35S promotor. Northern and western blot analysis showed that the tachyplesin I gene was expressed in transgenic plants. Small tubers of 17 transgenic clones were screened twice for soft rot resistance to Erwinia carotovora ssp. atroseptica. Under aerobic or anaerobic conditions, transgenic clones showed slightly less rot than control tubers.Abbreviations AP acidic carboxyl terminal polypeptide - Eca Erwinia carotovora ssp. atroseptica - Ecc E. carotovora ssp. carotovora - Ech E. chrysanthemi - IF intercellular fluid - SP signal peptide - TPNI (tpnI) tachyplesin I     

Root growth and nitrate utilization of maize cultivars under field conditions

In a 2-year field study conducted on a high fertilized Gleyic Luvisol in Stuttgart-Hohenheim significant differences among 10 maize cultivars were observed in soil nitrate depletion. The different capability of the cultivars to utilize nitrate particularly from the subsoil was positively correlated with (a) shoot N uptake at maturity, and (b) root length density (L_v) in the subsoil layers at silking. Critical root length densities for nitrate uptake were estimated by (a) calculating uptake rates per unit root length (U), (b) subsequent calculation of needed nitrate concentration in soil solution (C₁) to sustain calculated U according to the Baldwin formula, and (c) reducing measured L_v and proportionate increase of U until needed concentration equaled measured concentration. Uptake rate generally increased with soil depth. Critical root length densities for cultivar Brummi (high measured root length densities and soil nitrate depletion) at 60–90 cm depth ranged from 7 % (generative growth) to 28 % (vegetative growth) of measured L_v Measured root length density of each other cultivar was higher than critical root length density for Brummi indicating that the root system of each cultivar examined would have been able to ensure N uptake of Brummi. Positive relationships between root length density and nitrate utilization as indicated by correlation analysis therefore could not be explained by model calculations. This might be due to simplifying assumptions made in the model, which are in contrast to non-ideal uptake conditions in the field, namely irregular distribution of roots and nitrate in the soil, limited root/soil contact, and differences between root zones in uptake activity. It is concluded from the field experiment that growing of cultivars selected for high N uptake-capacity of the shoots combined with high root length densities in the subsoil may improve the utilization of a high soil nitrate supply.     

草木灰对四种松属种子发芽和幼苗生长的影响

火干扰不仅影响森林生态系统的结构与功能,而且影响群落更新与演替。为了研究草木灰对4种松属种子萌芽和幼苗生长的影响,在湖南省株洲市黄丰桥林场采集马尾松、云南松、湿地松和火炬松种子,以马尾松次生林火烧迹地的草木灰为基质,设置对照和3个草木灰处理,进行播种试验及生长观测。结果表明:(1)草木灰处理下4个物种的种子发芽率比对照试验低,并呈现随草木灰含量的增加而降低的趋势,低草木灰含量处理马尾松种子发芽率不及对照一半,中、高草木灰含量处理发芽率更低;云南松、湿地松和火炬松种子发芽率规律类似于马尾松,而高草木灰含量处理发芽率为0。(2)培养皿播种平均发芽时间比花盆播种长,无论草木灰处理还是培养条件(培养皿或花盆),马尾松和云南松种子平均发芽时间比湿地松和火炬松短。(3)4个物种种子播种14周后,对照试验中马尾松和云南松幼苗死亡率最低,而火炬松和湿地松幼苗死亡率相对增加。(4)播种14周后不同试验处理4个物种幼苗生长差异不明显。火炬松、湿地松、云南松和马尾松幼苗的单株平均干重分别达0.038、0.031、0.027、0.024 g。各物种叶干重按降序排列依次是火炬松(0.026 g)湿地松(0.019 g)云南松(0.017 g)马尾松(0.016 g),根和茎的干重比重相当,约占对应物种幼苗叶干重的三分之一。研究表明以草木灰为培养基质,马尾松和云南松种子的发芽率较高,平均发芽时间较短,更适合作为火烧迹地植被恢复先锋树种,为火干扰后选择人工促进天然更新树种提供参考。     

Nutrient status of vegetation grown in alkaline bauxite processing residue amended with gypsum and thermally dried sewage sludge - A two year field study

Although the treatments for overcoming the high pH and exchangeable sodium percentage (ESP) of bauxite residue are well known, there is little information on long-term nutrient management of vegetation after rehabilitation. The present study examined the chemical and physical amendment of fine fraction residue (red mud) at the Aughinish Alumina Ltd. Bayer Plant, Ireland followed by a two-year field investigation. Gypsum and sewage sludge were incorporated into the residue and amended mud sown with Lolium perenne and Holcus lanatus. Aerial portions were harvested and nutrient composition determined annually for the first two years growth. Amended substrate was low in manganese and magnesium. After year one herbage contained adequate calcium levels, but there were deficiencies for nitrogen, manganese, potassium and magnesium. Sodium levels were not considered excessive and levels declined further in year two. Levels for nitrogen, calcium, manganese, magnesium, phosphorous and potassium were also reduced in the second year. As levels were already deficient in year one the further decreases suggest severe nutrient shortage in the residue substrate. For long-term success of revegetation of bauxite residue, even after gypsum and organic amendment, the deficiencies of nutrients in the substrate must be overcome.     

镇江香醋核心酿造微生物醋酸杆菌和乳酸杆菌共培养对生长代谢的影响

[目的]研究镇江香醋酿造过程核心功能微生物醋酸杆菌属与乳酸杆菌属菌株之间的相互作用关系.[方法]本文以分离到的镇江香醋酿造中的核心微生物2株醋酸杆菌和8株孔酸杆菌为研究对象,构建醋酸杆菌和乳酸杆菌共培养发酵体系,比较异位与原位条件下,纯培养及共培养中菌株的生长和代谢(包括还原糖、乙醇和总酸等含量)差异;采用GC-MS检...     

筛选抑制酿酒酵母生长的人类基因

【目的】基于人类基因文库,构建一个筛选抑制酿酒酵母生长的人类基因的方法,并运用此方法筛选含有生长抑制性人源蛋白质的酿酒酵母,用于分析人类基因的生理功能及其抑制剂的寻找。【方法】利用Gateway~(TM)重组技术将人类蛋白质编码基因构建到酿酒酵母表达质粒中。得到的质粒分别转化酿酒酵母细胞中,分析哪些基因的表达会抑制酿酒酵母的生长,并用绿色荧光蛋白标签对典型候选基因在酿酒酵母中的定位进行观察。【结果与结论】本研究建立了抑制酿酒酵母生长的人类基因的筛选方法,并运用此方法成功地从2991个人类蛋白质编码基因中筛选到29个显著抑制酿酒酵母生长的基因。其中一些是引起人类疾病的致病基因。例如,PDLIM4参与到骨质疏松症和前列腺癌的形成和发展,但其生理功能尚不清楚。我们的研究可能为揭示这些候选基因的功能和调节机制提供新的途径。     

Ethylene advances the transition from vegetative growth to flowering in Arabidopsis thaliana

The transition from vegetative growth to flowering is the most drastic change in plant development. In order to examine the involvement of ethylene in growth transition, we compared the development of ethylene-related mutants, eto1, etr1, ein2-1 and ein3-1, with the wild type (WT) in Arabidopsis thaliana. The ethylene sensitivity of two WT and the mutants is decreased in the following order: eto1 = WT < ein3-1 < ein2-1 = etr1-1. Bolting time was also delayed in nearly the same order: eto1 < WT < ein3-1 < ein2-1 < etr1. Leaf numbers increased according to the delay of bolting time, indicating that the delay of bolting time was caused by the delay of transition from vegetative to reproductive growth. Other growth parameters, including leaf area and number of flowers opening at the same time, increased in the same order, indicating that these changes were caused by a single factor, the amount of ethylene signal which was transferred though an ethylene signal transduction pathway. These results suggest that ethylene is involved in the transition from vegetative to reproductive growth in Arabidopsis thaliana.     

Genetic variation of Carthamus tinctorius L. and related species revealed by SRAP analysis

Genetic diversity of 23 populations of Carthamus tinctorius L. and two populations of Carthamus lanatus L. in China was investigated using Sequence-related Amplified Polymorphism (SRAP). All populations could be uniquely distinguished by 30 primer combinations with 483 bands and 274 polymorphic bands which generated 57% of polymorphic ratio. Unweighed pair-group method of with arithmetical averages (UPGMA) cluster analysis enabled construction of a dendrogram for estimating genetic distances among different populations. The extreme variation was observed when No. 4 cultivated and No. 13 wild population of C. lanatus were grouped at GS = 0.58, and separated from 23 populations of C. tinctorius at GS = 0.10. The result suggested that the cultivated and wild populations of C. lanatus had close relationship with each other and far relationship with C. tinctorius. Dendrogram also revealed a large genetic variation in 23 C. tinctorius populations; different primer combinations allowed them distinctly distinguished one from others with relatively low genetic similarity. Furthermore, five typical representative fragments in C. lanatus were obtained by four most informative primer combinations, which provided a possibility to distinguish C. lanatus from the C. tinctorius evidently.     

Influence of phosphorus level on VA Mycorrhizal colonization and growth of cowpea cultivars

Vesicular-arbuscular mycorrhizal (VAM) associations often vary according to the abundance of available soil phosphorus (P). Therefore, understanding the response of crop plants to colonization by VAM fungi necessitates the study of the response of colonized and noncolonized plants, from a range of cultivars, to differing levels of P. Cowpea is grown throughout the world, often on impoverished soils in which it can benefit from formation of mycorrhizae. The present study was conducted to determine the response of four cultivars of cowpea (Vigna unguiculata (L.) Walp.), varying in nitrogen fixation capacity, to inoculation withGlomus fasciculatum at four levels of added P in the rooting medium. In a greenhouse experiment, four cowpea cultivars, Mississippi Silver, Brown Crowder, Six Week Browneye and MI 35, were grown with and without the mycorrhizal fungus at four levels of added P, 0, 10, 20 and 30 ppm. Root colonization (%) was negatively correlated with P content of the growth medium and shoot P concentration. Intraspecific variability was shown for shoot dry weight and leaf area in response to inoculation withG. fasciculatum at different P levels. The range of P required in the growth medium which allowed benefit fromG. fasciculatum was identified for individual cultivars using shoot dry weight and leaf area, and collectively across cultivars for other parameters.     

Evaluation of the bioremediatory potential of several species of the red alga <Emphasis Type="BoldItalic">Porphyra</Emphasis> using short-term measurements of nitrogen uptake as a rapid bioassay

Rates of inorganic nitrogen uptake by three Northeast US and three Asian species of Porphyra were compared in short-term incubations to evaluate potential for longer term and larger scale examination of bioremediation of nutrient-loaded effluents from finfish aquaculture facilities. The effects of nitrogen (N) species and concentration, temperature, acclimation history, and irradiance were investigated. Uptake rates increased ca. nine-fold from 20 to 150 μM N. Nitrate and ammonium uptake occurred at similar rates. Irradiance had a strong effect, with uptake at 40 μmol photons m⁻² s⁻¹only 55% of uptake at 150 μmol photons m⁻² s⁻¹. N-replete tissue took up inorganic nitrogen at rates that averaged only 60% of nutrient-deprived tissue. Although there were species (P. amplissima > (P. purpurea = P. umbilicalis)) and temperature effects (10 ^°C>5 ^°C>15 ^°C), interactions among factors indicated that individual species be considered separately. Overall, P. amplissima was the best Northeast US candidate. It took up ammonium at faster rates than other local species at 10 and 15 ^°C, two temperatures that fall within the expected range of industrial conditions for finfish operations.     

Expression analyses of Arabidopsis oligopeptide transporters during seed germination, vegetative growth and reproduction

AtOPT promoter-GUS fusions were constructed for six of the nine known, putative oligopeptide transporters (OPTs) in Arabidopsis thaliana and used to examine AtOPT expression at various stages of plant development. AtOPT1, AtOPT3, AtOPT4, AtOPT6 and AtOPT7 were expressed in the embryonic cotyledons prior to root radicle emergence. Except for AtOPT8, which gave weak expression, all AtOPTs were strongly expressed in post-germinative seedlings with strongest expression in vascular tissues of cotyledons and hypocotyls. Preferential expression of AtOPTs in vascular tissues was also observed in cotyledons, leaves, hypocotyls, roots, flowers, siliques, and seed funiculi of seedlings and adult plants. Differential tissue-specific expression was observed for specific AtOPTs. For example, AtOPT1, AtOPT3 and AtOPT8 were uniquely expressed in pollen. Only AtOPT1 was expressed in growing pollen tubes, while only AtOPT6 was observed in ovules. AtOPT8 was transiently expressed in seeds during early stages of embryogenesis. Iron limitation was found to enhance expression of AtOPT3. These data suggest distinct cellular roles for specific AtOPTs including nitrogen mobilization during germination and senescence, pollen tube growth, pollen and ovule development, seed formation and metal transport.     

Use of Tissue Culture and Biotechnology for the Genetic Improvement of Watermelon

Watermelon is an important vegetable crop world-wide with over 81 million metric tons produced annually. Despite these high production figures, million of metric tons of fruit are lost in fields to disease. Genetic improvement through tissue culture and biotechnology offer potential routes of improving fruit harvest by offering higher quality products, like seedless fruit, or by introducing recombinant genes or generating somaclonal variants with improved resistance to biotic or abiotic stresses. The purpose of this review is to highlight how tissue culture and biotechnology have been used for the genetic improvement of watermelon and provide suggestions for future application of these methods to facilitate further genetic improvement.     

A genetic classification of potato cultivars based on allozyme patterns

Summary A total of 25 potato isozymes were characterized by the numbers and relative mobilities of their allozymes, the subunit number, the subcellular localization, and the patterns of tissue expression. Using hierarchically ordered phenotype arrays at 9 of these isozymes, we were able to construct a dichotomous classification table for a total of 74 potato varieties, including those of most agronomical interest in Europe and North America.