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2.
The plant cell changes its cell wall architecture during growth and development through synthesis and degradation of wall polysaccharides. Changes of chemical components in the cell wall include not only the synthesis and degradation but also the shift of molecular-weight distribution of certain species of the component polysaccharides. The changes in chemical structure, in turn lead to alteration of physical properties of the cell wall. Changes of physical parameters of cell walls obtained by a physical method accord with the biochemical degradation of polysaccharides. The changes in chemical structures of the cell wall are regulated by plant hormones, stress signals and gene expression. The physical and chemical studies of the cell wall have disclosed that degradation and/or depolymerization of wall polysaccahrides causes decrease in viscosity of the cell wall, leading further extension of the cell wall even under the unchanged osmotic relation. Furthermore, cell walls of outer and inner tissues play different regulatory roles in tissue growth and stem strength was governed by the number of cellulose molecules in the cell wall. Recipient of the Botanical Society Award for Young Scientists, 1990.  相似文献   
3.
玉米根ABA结合蛋白的亚细胞定位及动力学性质   总被引:9,自引:0,他引:9  
以玉米(Zea maysL.)根或胚芽鞘为材料,经匀浆、分级离心得到胞质部分和膜部分(微粒体),进一步用6.2% (W/W ) Dextran T500 和PEG 3350 两相系统制备质膜,用1% 和8% (W /W) Dextran T70 梯度离心制备液泡膜. 电镜鉴定及多种标志酶检测表明,制备获得了高纯度正向型质膜和富含液泡膜的组分,其它内膜的污染很少. 用微量放射配体结合(MRLB)实验证明,玉米根微粒体的ABA专一性结合位点主要分布在液泡膜和质膜上,这两种膜组分与ABA 的特异结合活性分别为2485.4 fm ol/m g protein 和1257.3 fm ol/m g pro-tein,玉米根段胞质部分结合活性最低(差一个数量级).质膜上ABA-BP与ABA 的结合平衡解离常数(KD)为1.57 nm ol/L.  相似文献   
4.
Whole-plant ABA flux and the regulation of water loss in Cedrella odorata   总被引:2,自引:0,他引:2  
Three-month-old Cedrella odorata seedlings were exposed to a soil-drying treatment. During this period, xylem sap was periodically collected from the plant by applying pneumatic pressure to the roots. This also allowed whole-plant water status to be measured by recording the balancing pressure applied. The concentration of ABA in xylem sap (C) was related to the whole-plant transpiration rate (V) which was measured with a sap flow gauge. The analysis of these paired measurements centred on how the reciprocal of C (R) varied with respect to V. This revealed that (1) the observed increases in C could not be explained by the reductions in V alone, (2) initially, decreases in V were associated with proportional increases in the whole-plant ABA flux (M), and (3) this relationship broke down at low values of V since zero flow was associated with a finite value for C estimated to be 41 pmol ABA mmol?1 H2O. A simple static model is developed from the observations that is able to explain the data well, and the results are discussed in terms of the effects of ABA on stomatal conductance (gsw).  相似文献   
5.

Background

Stomatal guard cells are the regulators of gas exchange between plants and the atmosphere. Ca2+-dependent and Ca2+-independent mechanisms function in these responses. Key stomatal regulation mechanisms, including plasma membrane and vacuolar ion channels have been identified and are regulated by the free cytosolic Ca2+ concentration ([Ca2+]cyt).

Scope

Here we show that CO2-induced stomatal closing is strongly impaired under conditions that prevent intracellular Ca2+ elevations. Moreover, Ca2+ oscillation-induced stomatal closing is partially impaired in knock-out mutations in several guard cell-expressed Ca2+-dependent protein kinases (CDPKs) here, including the cpk4cpk11 double and cpk10 mutants; however, abscisic acid-regulated stomatal movements remain relatively intact in the cpk4cpk11 and cpk10 mutants. We further discuss diverse studies of Ca2+ signalling in guard cells, discuss apparent peculiarities, and pose novel open questions. The recently proposed Ca2+ sensitivity priming model could account for many of the findings in the field. Recent research shows that the stomatal closing stimuli abscisic acid and CO2 enhance the sensitivity of stomatal closing mechanisms to intracellular Ca2+, which has been termed ‘calcium sensitivity priming’. The genome of the reference plant Arabidopsis thaliana encodes for over 250 Ca2+-sensing proteins, giving rise to the question, how can specificity in Ca2+ responses be achieved? Calcium sensitivity priming could provide a key mechanism contributing to specificity in eukaryotic Ca2+ signal transduction, a topic of central interest in cell signalling research. In this article we further propose an individual stomatal tracking method for improved analyses of stimulus-regulated stomatal movements in Arabidopsis guard cells that reduces noise and increases fidelity in stimulus-regulated stomatal aperture responses ( Box 1). This method is recommended for stomatal response research, in parallel to previously adopted blind analyses, due to the relatively small and diverse sizes of stomatal apertures in the reference plant Arabidopsis thaliana.

Box 1. Improved resolution of stimulus-induced stomatal movements in guard cells by tracking of individual stomatal apertures

Arabidopsis guard cells have become a prime model system for analysing signal transduction, since early research combining genetic and ion channel analyses in this system (Ichida et al., 1997; Pei et al., 1997, 1998; Roelfsema and Prins, 1997). Arabidopsis stomata are small relative to other stomatal model systems and stomatal apertures of various plant types including Arabidopsis are known to show variability in the size of individual stomatal complexes and also variability in the opening apertures of stomata of similar size in a given leaf (Gorton et al., 1988; Mott and Buckley, 2000; Mott and Peak, 2007). Thus stomatal aperture measurements are expected to show a clear degree of statistical variation. Use of blind experiments, in which the genotype and, when possible, the stimulus being applied to guard cells is unknown to the experimenter (Murata et al., 2001) has been employed by several laboratories, has become a standard in the field and has aided in addressing the above limitations of the range of stomatal aperture sizes found under any given condition.Research in our laboratory has shown that a major additional improvement in experiments can be made, by adding imaging of the same individual stomatal apertures over time (Allen et al., 2001; Mori et al., 2006; Vahisalu et al., 2008; Siegel et al., 2009), while performing blind experiments. In such ‘stomatal tracking’ experiments the lower side of a leaf is attached to a glass coverslip in an extracellular incubation medium (Webb et al., 2001; Young et al., 2006). The mesophyll and upper leaf epidermis are removed surgically for better optical resolution of stomatal apertures in the intact lower leaf epidermis (Young et al., 2006). For stimulus-induced stomatal closing analyses, a field of well-opened stomata is located and images are captured (e.g. using Scion Image software) for later analyses and data storage. The bottom (dry side) of coverslips can be marked with colour marker pens to label grids in the regions where apertures where imaged, for finding these same stomata subsequently if needed. Images of the same stomatal apertures are taken over time and can be stored for later analyses of individual stomatal apertures and for deposition of image files. While this approach has been used as a standard for imposed Ca2+ oscillation studies (Allen et al., 2001; Mori et al., 2006; Vahisalu et al., 2008; Fig. 4), we have found that this method also substantially improves stomatal movement response analyses to any given stimulus (Siegel et al., 2009; see Figs 1 and 4 and, Box Fig. 1). For example, while individual stomata are known to have diverse apertures (e.g. Box Fig. 1C), the relative responses of wide open stomata and smaller stomatal apertures to ABA or to CO2 were comparable (Fig. 1 and Box Fig. 1; Siegel et al., 2009). Note that this method has previously been proposed and used in Vicia faba (Gorton et al., 1988), for which stomata exhibit relatively weak ABA and CO2 responses, compared with, for example, Arabidopsis. We propose that this simple image-capturing approach, together with blind analyses, be used as a standard for stomatal response research in arabidopsis. Our research experience with this method shows that this approach will aid in greatly improving resolution and robustness and in defining the functions of individual Ca2+-independent and Ca2+-dependent components and mechanisms in stomatal response analyses. Open in a separate windowBox Fig. 1.ABA-induced stomatal closing of individually tracked stomatal apertures. (A) Average individually tracked stomatal apertures in the presence of 50 µm Ca2+ (open triangles) and in the presence of 200 nm free Ca2+ (open squares) in the bath solution from three experiments are shown and were normalized to the stomatal apertures at time = 0. (B, C) ABA-induced stomatal closing in the presence of 50 µm Ca2+ in five individually tracked stomatal apertures. In (A; open triangles) normalized stomatal apertures of the same stomata depicted in (B) and (C) are shown. Methods used in these experiments tracking individual stomatal apertures are described in Siegel et al. (2009). ABA-induced stomatal closing experiments are reproduced from Siegel et al. (2009) with permission of the publisher.  相似文献   
6.
Water stress-induced ABA accumulation is a cellular signaling process from water stress perception to activation of genes encoding key enzymes of ABA biosynthesis, of which the water stress-signal perception by cells or triggering mechanism of the ABA accumulation is the center in the whole process of ABA related-stress signaling in plants. The cell biological mechanism for triggering of ABA accumulation under water stress was studied in leaves ofVicia faba. Mannitol at 890 mmol ·kg-1 osmotic concentration induced an increase of more than 5 times in ABA concentration in detached leaf tissues, but the same concentration of mannitol only induced an increase of less than 40 % in ABA concentration in protoplasts. Like in detached leaf tissues, ABA concentration in isolated cells increased more than 10 times under the treatment of mannitol at 890 mmol · kg-1 concentration, suggesting that the interaction between plasmalemma and cell wall was essential to triggering of the water stress-induced ABA accumulation. Neither Ca2+-chelating agent EGTA nor Ca2+channel activator A23187 nor the two cytoskeleton inhibitors, colchicine and cytochalasin B, had any effect on water stress-induced ABA accumulation. Interestingly water stress-induced ABA accumulation was effectively inhibited by a non-plasmalemma-permeable sulfhydryl-modifier PCMBS (p-chloromercuriphenyl-sulfonic acid), suggesting that plasmalemma protein(s) may be involved in the triggering of water stress-induced ABA accumulation, and the protein may contain sulfhydryl group at its function domain.  相似文献   
7.
应用酶联免疫技术,研究了冬小麦品种燕大1817 在不同光周期条件下,体内内源玉米赤霉烯酮(ZEN) 和ABA 含量的变化。结果表明,冬小麦品种燕大1817 具有短日春化性,苗期经4 周SD 处理后转到LD 下能正常抽穗。SD 诱导春化的幼苗茎尖和叶片中ZEN 含量高于未经诱导的LD 幼苗,而在两种光周期条件下生长的幼苗中ABA 含量变化趋势并无明显差异。马拉硫磷( MAL) 抑制SD 幼苗体内ZEN 含量高峰的出现,也部分抑制抽穗;外源ZEN 可部分抵消MAL对植株的影响,降低茎尖内源ABA 含量,并有促进小麦拔节的作用。说明在冬小麦短日春化过程中,ZEN 具有促进作用,而ABA 没有直接影响。  相似文献   
8.
9.
Abscisic acid (ABA) is a plant hormone involved in the response to environmental stress. Recently, ABA has been shown to be present and active also in mammals, where it stimulates the functional activity of innate immune cells, of mesenchymal and hemopoietic stem cells, and insulin-releasing pancreatic β-cells. LANCL2, the ABA receptor in mammalian cells, is a peripheral membrane protein that localizes at the intracellular side of the plasma membrane. Here we investigated the mechanism enabling ABA transport across the plasmamembrane of human red blood cells (RBC). Both influx and efflux of [3H]ABA occur across intact RBC, as detected by radiometric and chromatographic methods. ABA binds specifically to Band 3 (the RBC anion transporter), as determined by labeling of RBC membranes with biotinylated ABA. Proteoliposomes reconstituted with human purified Band 3 transport [3H]ABA and [35S]sulfate, and ABA transport is sensitive to the specific Band 3 inhibitor 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid. Once inside RBC, ABA stimulates ATP release through the LANCL2-mediated activation of adenylate cyclase. As ATP released from RBC is known to exert a vasodilator response, these results suggest a role for plasma ABA in the regulation of vascular tone.  相似文献   
10.
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