Identification of genes encoding photoconvertible (Class I) water-soluble chlorophyll-binding proteins from Chenopodium ficifolium

Photoconvertible water-soluble chlorophyll-binding proteins, called Class I WSCPs, have been detected in Chenopodiaceae, Amaranthaceae and Polygonaceae plant species. To date, Chenopodium album WSCP (CaWSCP) is the only cloned gene encoding a Class I WSCP. In this study, we identified two cDNAs encoding Chenopodium ficifolium Class I WSCPs, CfWSCP1, and CfWSCP2. Sequence analyses revealed that the open reading frames of CfWSCP1 and CfWSCP2 were 585 and 588 bp, respectively. Furthermore, both CfWSCPs contain cystein2 and cystein30, which are essential for the chlorophyll-binding ability of CaWSCP. Recombinant CfWSCP1 and CfWSCP2, expressed in Escherichia coli as hexa-histidine fusion proteins (CfWSCP1-His and CfWSCP2-His), formed inclusion bodies; however, we were able to solubilize these using a buffer containing 8 M urea and then refold them by dialysis. The refolded CfWSCP1-His and CfWSCP2-His could bind chlorophylls and exhibited photoconvertibility, confirming that the cloned CfWSCPs are further examples of Class I WSCPs.     

The Ecological Significance of Allelopathy in the Community Organization of Alhagi Graecorum Boiss

Field study revealed that species diversity index of the community was 0.597. The data of interspecific association index of Alhagi graecorum and each of its associates, Chenopodium murale, Glinus lotoides and Malva parviflora, were 0.35, 0.41 and 0.33, respectively. Therefore, a net negative association and low diversity among the species were the main characters of the community. Laboratory experiments verified the role played by competition and allelopathy in this community organization. The bioassay results indicated that A. graecorum exhibited phytotoxic activity on the tested species. Accordingly, water-borne allelopathic compounds may be released from A. graecorum into the environment and suppress the growth of its associates where they were not able to compete with A. graecorum in the field, so the latter species become dominant.     

Two Proton Pumps Operate in Parallel Across the Tonoplast of Vacuoles Isolated from Suspension Cells of Chenopodium rubrum L.*

The kinetics of vacuolar acidification upon addition of ATP and/or pyrophosphate (PPi) has been assayed on single immobilized vacuoles by computer-aided microfluorimetry of 9-aminoacridine, and by acridine orange absorption photometry on vacuole suspensions isolated from green suspension cells of Chenopodium rubrum L. Two proton pumps at the tonoplast, an ATPase and a pyrophosphatase (PPase), operate in parallel to acidify the vacuole with different contributions adding up to a transtonoplast Δ pH of 2.6 pH units at external pH 7.2. The saturable components of proton pumping reach half maximal velocity with 0.32 ± 0.06 mM ATP and 23 ± 2.5 μM PPi, respectively. At saturating substrate concentrations, ATPase and PPase hydrolyse ATP and PPi, respectively, at a ratio of 2.3. The same ratio holds for the corresponding proton fluxes maintaining a given steady-state vacuolar pH. We conclude that both pumps operate at the same stoichiometry.     

青橄榄浸膏的提取及其抗氧化活性研究

为优化青橄榄浸膏提取工艺,并探讨其抗氧化性。以茂名盛产的青橄榄为原料,采用超声波辅助乙醇提取法,以总黄酮和总多酚得率为评价指标,考察各因素对青橄榄浸膏提取效果的影响。采用邻苯三酚自氧化法、结晶紫法和DPPH清除能力评价青橄榄浸膏的抗氧化活性。结果显示,浸膏的最佳提取工艺为:乙醇体积分数70%,料液比1∶18 (g∶mL),超声提取温度50℃,时间6 min(超声提取阶段);单纯有机溶剂提取温度60℃,时间45 min(有机溶剂浸提阶段);此条件下总黄酮得率为1. 76%,总多酚得率为15. 53%。终产物浸膏在0. 3 mg/mL浓度下对超氧阴离子自由基抑制率为22. 74%,相当于同等质量浓度的抗坏血酸抑制效果的23. 47%;在0. 02 mg/mL浓度下对羟基自由基的清除率为67. 32%,相当于同等质量浓度的抗坏血酸清除效果的112. 58%;在0. 2 mmol/mL的DPPH溶液体系中,0. 15 mg/mL的浸膏对DPPH的清除率为95. 40%,相当于同等质量浓度的抗坏血酸清除效果的140. 83%;总体来讲,浸膏具有良好的抗氧化能力,虽然对超氧阴离子自由基抑制率弱于抗坏血酸,但羟基自由基的清除率及DPPH清除率均优于抗坏血酸。     

Methyl jasmonate differentially affects tocopherol content and tyrosine amino transferase activity in cultured cells of Amaranthus caudatus and Chenopodium quinoa

Tocopherols are lipid-soluble compounds synthesised exclusively by photosynthetic organisms. In this study, in vitro callus cultures were established from two plants that are naturally rich in tocopherols, Amaranthus caudatus and Chenopodium quinoa, in order to examine whether callus cultures were able to produce these compounds at levels comparable to those observed in planta . In both species, cotyledon explants produced the best callus induction and, once established, callus cultures were grown under two different hormonal treatments to check for effects of growth and to induce chloroplast differentiation in the cells. A rapid differentiation of chloroplasts occurred only in C. quinoa cell aggregates grown in the presence of benzyladenine, leading to the production of a homogeneous green callus. In both species, only α-tocopherol was produced by callus cultures, although levels were much lower than in planta, and the production was not influenced by the hormonal conditions. Interestingly, cell cultures of the two species responded in different ways to methyl jasmonate (MJ). In A. caudatus cultures, treatment with 100 μ m MJ increased the production of α-tocopherol up to fivefold, and the inductive effect was influenced by the hormonal composition of the medium. This increase in α-tocopherol was associated with a proportional increase in tyrosine aminotransferase (TAT) activity, one of the key enzymes involved in tocopherol biosynthesis. By contrast, in C. quinoa cultures, elicitation with MJ did not have any effect, neither on tocopherol production, nor on TAT activity. These results are discussed in relation to chloroplast differentiation and the interplay between jasmonates and phytohormones.     

铺地藜——中国藜属一新归化种

报道中国藜属一新归化种——铺地藜(Chenopodium pumilio R. Br.)。     

Heat-stable chloroplastic Cu/Zn superoxide dismutase in Chenopodium murale

Chenopodium murale is a weed species having wide adaptation to different climatic regimes and experiences a temperature range of 5-45 degrees C during its life span. Higher temperatures may result in heat stress, which induces higher ROS production leading to oxidative stress in the plant. Superoxide dismutase enzyme (SOD, EC.1.15.1.1) is ubiquitous, being widely distributed among O(2)(-) consuming organisms and is the first line of defense against oxidative stress. In this study, we have characterized the thermostability of the SOD isozymes from C. murale in vitro. The leaf protein extracts, thylakoidal and stromal fractions were subjected to elevated temperatures ranging from 50 degrees C to boiling and analyzed for activity and isoform pattern of SOD. Out of six SOD isoforms, SOD V showed stability even after boiling the extract for 10min. Under high temperature treatment (>60 degrees C) there was an appearance of a new SOD band with higher electrophoretic mobility. The inhibitor studies and subcellular analysis revealed that the SOD V isoform was a chloroplastic Cu/Zn SOD. The stromal Cu/Zn SOD (SOD V) was more stable than the co-migrating thylakoidal isozyme at 80 degrees C and boiling for 10min. Hence, we report an unusual, constitutive thermostable chloroplastic Cu/Zn SOD from C. murale, which may contribute towards its heat tolerance.     

Influence of photoinhibition on electron transport and photophosphorylation of isolated chloroplasts

The effects of a photoinhibition treatment (PIT) on electron transport and photophosphorylation reactions were measured in chloroplasts isolated from triazine-resistant and susceptible Chenopodium album plants grown under high and low irradiance. Electron transport dependent on photosystem I (PSI) alone was much less affected by PIT than that dependent on both photosystem II (PSII) and PSI. There was a smaller difference in susceptibility to PIT between the photophosphorylation activitity dependent on PSI alone and that dependent on both PSII and PSI. Because in all cases photophosphorylation activity decreased faster upon PIT than the rate of electron transport, we conclude that photoinhibition causes a gradual uncoupling of electron transport with phosphorylation. Since the extent of the light-induced proton gradient across the thylakoid membrane decreased upon PIT, it is suggested that photoinhibiton causes a proton leakiness of the membrane. We have found no significant differences to PIT of the various reactions measured in chloroplasts isolated from triazine-resistant and susceptible plants. We have also not observed any significant differences to PIT of the photophosphorylation reactions in chloroplasts of plants grown under low irradiance, compared with those grown under high irradiance. However, the electron transport reactions in chloroplasts from plants grown under low irradiance appeared to be somewhat less sensitive to PIT than those grown under high irradiance.     

Semicontinuous cultivation of photoautotrophic cell suspension cultures in a 20 l airlift-reactor

An airlift-bioreactor system was established for semicontinuous growth of photosynthetically active plant cell suspension cultures in a controlled environment. The bioreactor unit was constructed as a conventional, internal draught tube airlift-reactor, which is characterized by a H D^-1 ratio of 2.9, a ratio of the cross-sectional area of the riser to the cross-sectional area of the downcomer of 0.25 and a surface area of 0.435 m² for illumination. Cultivation experiments could be scaled up to working volumes of maximal 20 1. Sixteen fluorescent tubes were fixed around the outer glass cylinder to provide cells continuously with light. An external cooling device was used to keep the temperature constantly at 27°C. Agitation as well as supply with CO₂ was performed by injecting air enriched with CO₂ through a ring-shaped sparger at the bottom of the vessel. A first set of experiments was carried out with a photoautotrophic culture of Chenopodium rubrum L. Cell material adapted to large scale culture conditions was used to inoculate a modified MS medium (Murashige & Skoog 1962) without any organic constituents. Under these conditions a biomass increase of 1870% was achieved in 18 days. Several physiological parameters (e.g. pigmentation, photosynthetic O₂ evolution, carbohydrate content) were measured routinely to elucidate the growth characteristics of large-scale grown Chenopodium cells. Electron microscopic photographs from different phases of culture growth clearly demonstrate the pattern of cellular development. Special emphasis was placed upon the differentiation of chloroplast ultrastructure. The presented data confirm the feasibility of large-scale culture techniques with photosynthetic active plant cell cultures.Abbreviations D diameter - DW dry weight - FW fresh weight - H height - K_La volumetric oxygen transfer coefficient (h^-1) - MES 2-(N-morpholino)-ethanesulfonic acid - specific growth rate (d^-1) - PAR photosynthetically active radiation (400–700 nm) - Pepcase phosphoenolpyruvate carboxylase - Rubisco ribulose-1,5-biphosphate carboxylase/oxygenase - t_d doubling time (d) - vvm (aeration volume) (medium volume)^-1 min^-1 Dedicated to Prof. F.-C. Czygan on the Occasion of his 60th Birthday     

人工促成檀香结香的研究

在自然情况下生长的檀香（ＳａｎｔａｌｕｍａｌｂｕｍＬ．）植株,约１０龄左右开始形成具芳香的心材（通称结香）,约３０—４０年方可砍伐利用．作者采用两年生的幼树,施用植物生长抑制剂ＰＧＩ１进行促成结香试验,结果证明采用１％３ｍｌ生长激素处理的植株,其檀香油和檀香醇的含量一般较对照和用水处理的植株高１—２倍．