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1.
Brown RC  Lemmon BE  Nguyen H 《Protoplasma》2003,222(3-4):167-174
Summary. Endosperm begins development as a single fertilized cell that undergoes many rounds of mitosis without cytokinesis resulting in a syncytium. The multinucleate cytoplasm is organized by nucleus-based radial microtubule systems into nuclear-cytoplasmic domains. When microtubules are organized into mitotic spindles, the integrity of the common cytoplasm is maintained by an unaltered network of filamentous actin. The first four rounds of mitosis result in the establishment of three developmental domains within the common cytoplasm. The spindles of the first two rounds of mitosis are oriented parallel to the long axis of the central cell, resulting in four nuclear-cytoplasmic domains in a filamentous arrangement. A switch in spindle orientation occurs in the third round of mitosis; all four spindles are oriented perpendicular to the long axis resulting in eight nuclear-cytoplasmic domains arranged in two adjacent files. Whereas the first three rounds of mitosis are synchronous, the fourth occurs as a wave of successive mitoses that begins at the micropylar pole. By the 16-nuclei stage, differences in nuclear shape, cytoskeletal arrays, and cytoplasmic characteristics mark the differentiation of the syncytium into micropylar, central, and chalazal developmental chambers. Nuclei in the micropylar chamber are fusiform and sheathed by parallel microtubules that flare from their tips, while those in the central and chalazal chambers are spherical. Nuclei in the central chamber are surrounded by radial microtubule systems, while those in the chalaza are enmeshed in a reticulum of microtubules. Whereas the cytoplasm in both micropylar and chalazal chambers is dense and nearly nonvacuolate, the syncytium in the central chamber consists of a single layer of evenly spaced nuclear-cytoplasmic domains surrounding a large central vacuole.Correspondence and reprints: Department of Biology, University of Louisiana at Lafayette, Lafayette, LA 70504-2451, U.S.A.Present address: Department of Plant Sciences, University of Arizona, Tucson, Arizona, U.S.A.  相似文献   

2.
The seed in the mature and dry state is metabolically inactive (quiescent) and is thus able to withstand extreme environmental conditions, such as drought and cold. Germination commences when the dry seed, shed from its parent plant, takes up water (imbibition) and ends when the root emerges through the seed coat. During seedling establishment, the reserves stored in the seed are metabolized, whereas the subsequent vegetative and reproductive growth is supported by photosynthesis. Here, we describe the functional characterization of the PH-START protein AtAPO1 (Arabidopsis thaliana APOSTART1), the putative homologue of PpAPO1 (Poa pratensis APOSTART1) in Arabidopsis thaliana. By using translational fusion of the AtAPO1 promoter to the uiaD gene and in situ hybridization analyses, we show that AtAPO1 is expressed in mature embryo sacs and developing embryos. The functional analysis of two at-apostart mutant alleles suggests that AtAPO1 is involved in the control of seed germination.  相似文献   

3.
Dovzhenko A  Dal Bosco C  Meurer J  Koop HU 《Protoplasma》2003,222(1-2):107-111
Summary. An efficient and fast regeneration system from cotyledon protoplasts was established for Arabidopsis thaliana accessions C24, Columbia, and Wassilewskija. Culture conditions and media compositions were optimised for the development of protoplasts embedded in thin alginate layers. Unexpectedly, the absence of cytokinins had a positive effect on cell development. Moreover, combined adjustment of -naphthylacetic acid and dicamba concentrations resulted in high plating efficiencies of up to 30%, followed by shoot regeneration within only 19 days after protoplast isolation. The protocol is reproducible, efficient, extremely fast, and regenerated plants are fertile. Thus, this cotyledon-based system could prove useful for studying plant cell and molecular biology in A. thaliana.Correspondence and reprints: Zentrum für angewandte Biowissenschaften, Sonnenstrasse 5, 79104 Freiburg, Federal Republic of Germany.Received December 9, 2002; accepted April 13, 2003; published online September 23, 2003  相似文献   

4.
 The process of endosperm development in Arabidopsis was studied using immunohistochemistry of tubulin/microtubules coupled with light and confocal laser scanning microscopy. Arabidopsis undergoes the nuclear type of development in which the primary endosperm nucleus resulting from double fertilization divides repeatedly without cytokinesis resulting in a syncytium lining the central cell. Development occurs as waves originating in the micropylar chamber and moving through the central chamber toward the chalazal tip. Prior to cellularization, the syncytium is organized into nuclear cytoplasmic domains (NCDs) defined by nuclear-based radial systems of microtubules. The NCDs become polarized in axes perpendicular to the central cell wall, and anticlinal walls deposited among adjacent NCDs compartmentalize the syncytium into open-ended alveoli overtopped by a crown of syncytial cytoplasm. Continued centripetal growth of the anticlinal walls is guided by adventitious phragmoplasts that form at interfaces of microtubules emanating from adjacent interphase nuclei. Polarity of the elongating alveoli is reflected in a subsequent wave of periclinal divisions that cuts off a peripheral layer of cells and displaces the alveoli centripetally into the central vacuole. This pattern of development via alveolation appears to be highly conserved; it is characteristic of nuclear endosperm development in angiosperms and is similar to ancient patterns of gametophyte development in gymnosperms. Received: 21 September 1998 / Revision accepted: 17 November 1998  相似文献   

5.
DEGP家族蛋白酶广泛分布于原核生物和真核生物细胞中。在拟南芥中有16个DEGP类似的蛋白酶,根据蛋白质组学数据,其中有4个定位于叶绿体中,分别命名为DEG1、DEG2、DEG5和DEG8。结合生物化学和分子生物学等研究手段对拟南芥叶绿体中的DEGP蛋白酶进行了分析,现有的研究初步证明了这些蛋白酶参与光系统II(PSII)复合物反应中心D1蛋白的降解,从而在PSII复合物的修复循环和功能维护中起重要作用。该文概述了拟南芥叶绿体中DEG蛋白酶的结构和功能的最新研究进展。  相似文献   

6.
自1979年Grove等首次从油菜(&.wM-。。WL·)花粉中分离出油菜素内酯(brassinolide,BR)以来,人们已在该激素的生理反应和对植物生长发育等方面进行了许多研究(Kalinich等1985,Mandava1988,吴登如和赵硫橘1993)。但由于这类激素在10-'mol/L浓度水平就能诱导大豆、水稻等多种植物细胞的生长和分裂(Sasse1991),而且在植物体内含量极低,因此用传统的方法研究它的作用方式非常困难。目前,利用激素突变体来研究激素代谢及其分子机制已有不少成功的例子,如生长素(Keily和Bradford1986,Lincoln等1990)、赤霉素(Singh…  相似文献   

7.
拟南芥室内培养技术   总被引:9,自引:1,他引:9  
本文报道了室内培养拟南芥的一些简便易行的改进技术.采用我们改进的营养土、蛭石、素沙混合培养介质和直播方式培养拟南芥,并根据其生物学特性在温度、空气湿度、土壤水分和光照等方面给予适当管理,能培养出生长更健壮、更好地满足实验要求的拟南芥植株.此外还介绍了播种、浇水、生育期调节、种子保存、病虫害防治和防混杂等环节的一些技巧措施.与其他培养方法相比,此法不仅简便、效果好,而且适合较简易的培养条件.  相似文献   

8.
Plasmodesmata in Arabidopsis thaliana suspension cells   总被引:2,自引:0,他引:2  
Bayer E  Thomas CL  Maule AJ 《Protoplasma》2004,223(2-4):93-102
Summary. A current challenge in plant biology is to identify the structural and functional components of plasmodesmata (PDs). The use of plant tissue as a source material for plasmodesmal characterisation has had limited success, so we have explored the frequency and features of PDs occurring in suspension cell cultures of Arabidopsis thaliana. This material has the advantages of homogeneity, quantity, and ease of disruption. Using light and electron microscopy and immunostaining for callose and calreticulin, we showed that suspension cells laid down abundant PDs in division walls, and that vestiges of these structures were retained as half PDs even when the cell-to-cell contacts were disrupted during culture growth. Although callose was a reliable marker for PD distribution, which was deposited in an organised collar around the neck of PDs, it was not abundant in unstressed cells. Calreticulin and the chemical stain 3,3-dihexyloxacarbocyanine iodide also provided useful markers when monitoring PDs in cell wall preparations by light microscopy. Purified cell walls were shown to be virtually free of contamination from cytoplasmic components, except for the presence of small amounts of cortical endoplasmic reticulum attached to PDs. Hence, clean cell walls from A. thaliana suspension cells provide a valuable resource for a proteomic approach to the analysis of plasmodesmal components.Correspondence and reprints: John Innes Centre, Norwich Research Park, Colney, Norwich NR4 7UH, United Kingdom.  相似文献   

9.
In the studies of nutritional absorption and metal toxicity in the root, it is important to grow plants without technical damage. We established a simple hydroponic culture system for Arabidopsis thaliana to obtain a healthy plant having a well-developed root system with many lateral roots. The phytotoxic effects of Cr, Cu, and Al ions were examined by FDA-PI staining using this culture system. The pattern of root inhibition varied with the ion, suggesting the usefulness of this culture system.  相似文献   

10.
The photorespiratory enzyme L-serine:glyoxylate amino- transferase (SGAT; EC 2.6.1.45) was purified from Arabidopsis thaliana leaves. The f'mal enzyme was approximately 80 % pure as revealed by sodium dodecyl sulfatepolyacrylamide gel electrophoresis with silver staining. The identity of the enzyme was confirmed by LC/MS/MS analysis. The molecular mass estimated by gel filtration chromato- graphy on Sephadex G-150 under non-denaturing conditions, mass spectrometry (matrix-assisted laser desorption/ ionization/time of flight technique) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis was 82.4 kDa, 42.0 kDa, and 39.8 kDa, respectively, indicating dimer as the active form. The optimum pH value was 9.2. The enzyme activity was inhibited by aminooxyacetate and β-chloro-L-alanine both compounds reacting with the carbonyl group of pyridoxal phosphate. The enzyme's transaminating activity with L-alanine and glyoxylate as substrates was approximately 55 % of that observed with L-serine and glyoxylate. The lower Kmvalue (1.25 mM) for L-alanine, compared with that of other plant SGATs, and the kcat/Km(Ala) ratio being approxi- mately 2-fold higher than kcat/Km(Ser) suggested that, during photorespiration, Ala and Ser are used by Arabidopsis SGAT with equal efficiency as amino group donors for glyoxylate. The equilibrium constant (Keq), derived from the Haldane relation, for the transamination reaction between L-serine and glyoxylate with the formation of hydroxypyruvate and glycine was 79.1, strongly favoring glycine synthesis. However, it was accompanied by a low Km value of 2.83 mM for glycine. A comparison of some kinetic properties of the studied enzymes with the recombinant Arabidopsis SGATs previously obtained revealed substantial differences. The ratio of the velocity of the transamination reaction with L-alanine and glyoxylate as substrates versus that with L-serine and glyoxylate was 1:1.8 for the native enzyme, whereas it was 1:7 for the recombinant SGAT. Native SGAT showed a much lower Km value for L-alanine compared to the recombinant enzyme.  相似文献   

11.
12.
Plant growth-promoting rhizobacteria (PGPR) colonize plant roots and exert beneficial effects on plant health and development. We are investigating the mechanisms by which PGPR elicit plant growth promotion from the viewpoint of signal transduction pathways within plants. We report here our first study to determine if well-characterized PGPR strains, which previously demonstrated growth promotion of various other plants, also enhance plant growth in Arabidopsis thaliana. Eight different PGPR strains, including Bacillus subtilis GB03, B. amyloliquefaciens IN937a, B. pumilus SE-34, B. pumilus T4, B. pasteurii C9, Paenibacillus polymyxa E681, Pseudomonas fluorescens 89B-61, and Serratia marcescens 90-166, were evaluated for elicitation of growth promotion of wild-type and mutant Arabidopsis in vitro and in vivo. In vitro testing on MS medium indicated that all eight PGPR strains increased foliar fresh weight of Arabidopsis at distances of 2, 4, and 6 cm from the site of bacterial inoculation. Among the eight strains, IN937a and GB03 inhibited growth of Arabidopsis plants when the bacteria were inoculated 2 cm from the plants, while they significantly increased plant growth when inoculated 6 cm from the plants, suggesting that a bacterial metabolite that diffused into the agar accounted for growth promotion with this strain. In vivo, eight PGPR strains promoted foliar fresh weight under greenhouse conditions 4 weeks after sowing. To define signal transduction pathways associated with growth promotion elicited by PGPR, various plant-hormone mutants of Arabidopsis were evaluated in vitro and in vivo. Elicitation of growth promotion by PGPR strains in vitro involved signaling of brassinosteroid, IAA, salicylic acid, and gibberellins. In vivo testing indicated that ethylene signaling was involved in growth promotion. Results suggest that elicitation of growth promotion by PGPR in Arabidopsis is associated with several different signal transduction pathways and that such signaling may be different for plants grown in vitro vs. in vivo.  相似文献   

13.
拟南芥养分离子转运蛋白研究进展   总被引:8,自引:2,他引:8  
养分离子的跨膜转运是细胞获取养分的重要环节,亦是植物在组织和器官水平上进行养分吸收运移的基础。文中综述了拟南芥中养分离子转运蛋白在基因克隆、序列与结构分析、功能鉴定、表达与调控方面的研究进展,其中着重讨论了这些转运蛋白在氮、磷和钾等营养元素吸收、运输、分配中的作用。  相似文献   

14.
绒毡层在拟南芥花药花粉发育过程中具有重要作用,包括分泌降解胼胝质的胼胝质酶、为花粉壁的形成提供原料以及为小孢子发育提供营养物质.本文通过对拟南芥雄性不育突变体st273的分析,研究了ST273基因在花药花粉发育过程中的功能.st273是通过T-DNA插入诱变野生型拟南芥得到的一株突变体,遗传分析表明st273是单隐性核基因控制的.利用图位克隆的方法对不育基因ST273进行了定位,结果表明ST273基因与拟南芥第三条染色体上分子标记CIW11连锁.生物信息学分析发现该分子标记附近有一个调控花粉发育的基因TDF1.测序分析结果表明在st273突变体中,TDF1基因第三个外显子上459位的碱基发生了由G459变成了A459的单碱基变化,导致ST273基因该位点提前终止突变.等位分析结果表明st273与tdf1是等位突变体.st273突变体营养生长期发育正常,但生殖生长发育出现异常.亚历山大染色结果显示st273突变体花药中没有花粉.组织切片观察结果表明,突变体花药绒毡层异常肥大且空泡化,四分体不能正常释放小孢子,最终无法形成花粉.这些结果揭示了ST273蛋白质参与调控了绒毡层和小孢子发育过程.  相似文献   

15.
Sulfurtransferases (STRs) catalyze the transfer of a sulfur atom from a donor to a suitable acceptor molecule. The Arabidopsis thaliana genome encodes 20 putative STR proteins. The biological functions of most are unclear. We found that STR1 and STR2 play important roles in embryo/seed development. Mutation of STR1 alone resulted in a shrunken seed phenotype, although growth and development of vegetative and reproductive organs were not affected. The shrunken seed phenotype was associated with the delayed/arrested embryo development, in most cases, at the heart stage. The embryo defect of str1 mutant is not fully penetrant. Approximately 12.5% of embryos developed further and formed normal looking seeds. In severely shrunken seeds, no embryo could be identified after seed collection. Partially shrunken seeds that contained viable embryos could still germinate. However, cotyledons of the seedlings from such seeds were abnormal. An STR1-GUS fusion reporter revealed that the STR1 gene was universally expressed, with high levels of expression in specific tissues/organs including embryos. The incomplete penetrance of str1 embryo/seed phenotype is a result of functional STR2. Single str2 mutant had no phenotype. However, no str1(-/-)/str2(-/-) double mutant embryos were able to develop past the heart stage. Furthermore, STR2 is haplo-insufficient in str1 mutant background, and str1(-/-)/str2(+/-) embryos were 100% lethal. These data provide new insights into the biological functions of the ubiquitous sulfurtransferase in Arabidopsis embryogenesis and seed development.  相似文献   

16.
We analyzed the complete genome sequence of Arabidopsis thaliana and sequence data from 83 genes in the outcrossing A. lyrata, to better understand the role of gene expression on the strength of natural selection on synonymous and replacement sites in Arabidopsis. From data on tRNA gene abundance, we find a good concordance between codon preferences and the relative abundance of isoaccepting tRNAs in the complete A. thaliana genome, consistent with models of translational selection. Both EST-based and new quantitative measures of gene expression (MPSS) suggest that codon preferences derived from information on tRNA abundance are more strongly associated with gene expression than those obtained from multivariate analysis, which provides further support for the hypothesis that codon bias in Arabidopsis is under selection mediated by tRNA abundance. Consistent with previous results, analysis of protein evolution reveals a significant correlation between gene expression level and amino acid substitution rate. Analysis by MPSS estimates of gene expression suggests that this effect is primarily the result of a correlation between the number of tissues in which a gene is expressed and the rate of amino acid substitution, which indicates that the degree of tissue specialization may be an important determinant of the rate of protein evolution in Arabidopsis.  相似文献   

17.
18.
对苏铁(Cycas revoluta Thunb.)种子的种皮进行了解剖研究,结果表明:苏铁种子的种皮分为外种皮、中种皮和内种皮3层结构.外种皮含有角质化的表皮细胞、薄壁细胞以及少量的厚壁细胞和异细胞,布有树脂道、气室和4束大维管束;中种皮主要由厚壁细胞群和木质化纤维组成,种孔端有一条缝合线,种脐端有3个孔;内种皮由多层干瘪的薄壁细胞和脉络状维管束组成,种孔端有一层椭圆状保护膜.对外种皮和内种皮维管束进行观察研究发现:外种皮和内种皮的维管束分布方式及其结构存在明显差异,外种皮的维管束由种脐端顺着种子弧形走向种孔端,内种皮的维管束呈脉络状,形成维管网贯穿其中;内、外种皮维管束中均存在多种不同样式的导管.  相似文献   

19.
Plastid transformation in Arabidopsis thaliana   总被引:33,自引:0,他引:33  
Plastid transformation is reported in Arabidopsis thaliana following biolistic delivery of transforming DNA into leaf cells. Transforming plasmid pGS31A carries a spectinomycin resistance (aadA) gene flanked by plastid DNA sequences to target its insertion between trnV and the rps12/7 operon. Integration of aadA by two homologous recombination events via the flanking ptDNA sequences and selective amplification of the transplastomes on spectinomycin medium yielded resistant cell lines and regenerated plants in which the plastid genome copies have been uniformly altered. The efficiency of plastid transformation was low: 2 in 201 bombarded leaf samples. None of the 98 plants regenerated from the two lines were fertile. Received: 13 February 1998 / Revision received: 24 April 1998 / Accepted: 5 June 1998  相似文献   

20.
Complete structure of the chloroplast genome of Arabidopsis thaliana.   总被引:7,自引:0,他引:7  
The complete nucleotide sequence of the chloroplast genome of Arabidopsis thaliana has been determined. The genome as a circular DNA composed of 154,478 bp containing a pair of inverted repeats of 26,264 bp, which are separated by small and large single copy regions of 17,780 bp and 84,170 bp, respectively. A total of 87 potential protein-coding genes including 8 genes duplicated in the inverted repeat regions, 4 ribosomal RNA genes and 37 tRNA genes (30 gene species) representing 20 amino acid species were assigned to the genome on the basis of similarity to the chloroplast genes previously reported for other species. The translated amino acid sequences from respective potential protein-coding genes showed 63.9% to 100% sequence similarity to those of the corresponding genes in the chloroplast genome of Nicotiana tabacum, indicating the occurrence of significant diversity in the chloroplast genes between two dicot plants. The sequence data and gene information are available on the World Wide Web database KAOS (Kazusa Arabidopsis data Opening Site) at http://www.kazusa.or.jp/arabi/.  相似文献   

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