共查询到20条相似文献,搜索用时 15 毫秒
1.
The synergid cell: attractor and acceptor of the pollen tube for double fertilization 总被引:2,自引:0,他引:2
T. Higashiyama 《Journal of plant research》2002,115(2):0149-0160
In flowering plants, the egg cell is generally accompanied by two symmetrical cells, called synergid cells. As early as the
1870s, synergid cells were distinguished from egg cells and cooperation between synergid and egg cells was proposed; the term
"synergid" is derived from the Greek "synergos," which means "working together." The accumulation of morphological and genetic
data, and, more recently, the in vitro physiological analysis of the fertilization system of Torenia fournieri, have revealed that synergid cells work together with egg and central cells to accomplish double fertilization. This cooperation
is of crucial importance in the attraction and acceptance of the pollen tube. In this review article, I focus on the physiological
function and behavior of the synergid cell during the fertilization process.
Received: December 20, 2001 / Accepted: December 27, 2001 相似文献
2.
Pistil strategies controlling pollen tube growth 总被引:4,自引:0,他引:4
The progamic phase appears especially well suited for pollen-pistil interaction. During this phase the pistil supports pollen
germination and tube growth, and provides an adequate environment, nutrition and directional cues. However, this support does
not occur indiscriminantly and some mechanisms operating in the pistil constrain pollen tube growth. An active, regulated
constraint is the self-incompatibility reaction, but moderate restrictions of pollen tube growth also occur in compatible
matings. These moderate restrictions involve reduced support by the pistil and they operate through two main strategies; one
is by decreasing the amount of support and the other is by varying the time at which this support is provided. In this minireview,
we examine the evidence that is accumulating for both support and constraint of pollen tube growth by the pistil and discuss
the benefits of this dual system. 相似文献
3.
4.
Ultrastructure of the micropyle and its relationship to pollen tube growth and synergid degeneration in sunflower 总被引:1,自引:0,他引:1
Summary Ultrastructural studies made on the micropyle of sunflower before and after pollination resulted in the following observations. (1) The micropyle is closed instead of a hole or canal. The inner epidermis of the integument on both sides of the micropyle is in close contact at the apex of the ovule. The boundary between the two sides consists of two layers of epidermal cuticle. (2) The micropyle contains a transmitting tissue. The micropyle is composed of an intercellular matrix produced by the epidermal cells of the integument. (3) The micropyle is asymmetrical, and is much wider on the side proximal to the funicle. On the funicle side the cells adjacent to the micropyle are similar to those of the transmitting tissue: they have large amounts of intercellular matrix and contain abundant dictyosomes, rough ER, and starch grains, and provide an appropriate environment for growth of the pollen tubes. The cells distal to the funicle are rich in rough ER and lipid bodies; they lack large intercellular spaces. (4) The micropyle is variable in the axial direction, i.e., it is much larger and more asymmetric at the level distal to the embryo sac than at a level close to the embryo sac. After pollination, one to four pollen tubes are seen in a micropyle. During their passage through the micropyle, most pollen tubes are restricted to the side proximal to the funicle. There is a greater tendency (81%) for the degenerate synergid to be located toward the funicle, i.e., at the same side as the pollen tube pathway. The data indicate a close relationship between micropyle organization, orientation of pollen tube growth, and synergid degeneration. 相似文献
5.
Summary In pollen tubes, the motive force of cytoplasmic streaming is assumed to be generated by the sliding of the translocator associated with cell organelles along actin filaments. In the present study, the characteristics of the translocator were studied by reconstituting the movement of pollen tube organelles along characean actin bundles. Movement of pollen tube organelles proceeded from the pointed end to the barbed end of the actin filaments of the characean cells. The reconstituted movement was not inhibited by vanadate. KCL at higher concentrations inhibited the movement. Furthermore, heavy meromyosin (HMM) prepared from rabbit skeletal muscle myosin partially inhibited the reconstituted movement and pCMB-modified HMM inhibited it completely. The present results strongly support our previous conclusion that the translocator which generates the motive force of cytoplasmic streaming in pollen tube is myosin.Abbreviations AMP-PNP
adenylyl-imidodiphosphate
- ATP
adenosine-5-triphosphate
- ATP--S
adenosine-5-0-(3-thiotriphosphate)
- BSA
bovine serum albumin
- CCCP
carbonylcyanide m-chlorophenylhydrazone
- DTT
dithiothreitol
- EDTA
ethylenediamine tetraacetic acid
- EGTA
ethyleneglycol-bis-(-aminoethyl ether)N,N,N,N-tetraacetic acid
- HB
homogenization buffer
- HMM
heavy meromyosin
- NEM
N-ethylmaleimide
- pCMB
p-chloromercuribenzoic acid
- PIPES
piperazine-N,N-bis-(2-ethanesulfonic acid)
- PPi
pyrophosphate 相似文献
6.
花粉管生长调控的研究进展 总被引:5,自引:0,他引:5
本文从花粉管的生长特性、细胞质组成、细胞骨架、细胞壁的结构与合成、Ca2+通道和向性生长机制六个方面,综述了近些年来对花粉管生长调控研究的进展。 相似文献
7.
8.
Y. Iwanami 《Protoplasma》1980,102(1-2):111-115
Summary Effect of eight dicarboxylic acids and three monocarboxylic acids on pollen growth ofCamellia japonica was tested. While monocarboxylic acids inhibited pollen germination and pollen tube elongation, dicarboxylic acids, namely oxalic, succinic, suberic, adipic, sebacic, traumatic cis-1,2-cyclohexane dicarboxylic, and 3,3-diethyl glutaric acids stimulated pollen tube elongation stronger than indoleacetic acid. 相似文献
9.
10.
The growth of pollen tubes is characterized by an intense cytoplasmic streaming, during which the movements of smaller organelles (like secretory vesicles) and larger ones (including the generative cell and vegetative nucleus) are precisely coordinated. A well-characterized cytoskeletal apparatus is likely responsible for these intracellular movements. In recent years both microfilament and microtubule-based motor proteins have been identified and assumed to be the translocators of the several organelle categories. Their precise function during pollen tube growth is not yet clear, but apparently an actomyosin-based system is mainly responsible for pollen tube elongation. On the other hand, microtubules and microtubule-based motors have been thought to play a role in the maintenance of cell polarity. Both cytoskeletal systems (and their respective motor activities) could cooperate to ensure a precise regulation of pollen tube growth. 相似文献
11.
Pollen tube growth is localized at the apex and displays oscillatory dynamics. It is thought that a balance between intracellular
turgor pressure (hydrostatic pressure, reflected by the cell volume) and cell wall loosening is a critical factor driving
pollen tube growth. We previously demonstrated that water flows freely into and out of the pollen tube apical region dependent
on the extracellular osmotic potential, that cell volume changes reflect changes in the intracellular pressure, and that cell
volume changes differentially induce, increases or decreases in specific phospholipid signals. This article shows that manipulation
of the extracellular osmotic potential rapidly induces modulations in pollen tube growth rate frequencies, demonstrating that
changes in the intracellular pressure are sufficient to reset the pollen tube growth oscillator. This indicates a direct link
between intracellular hydrostatic pressure and pollen tube growth. Altering hydrodynamic flow through the pollen tube by replacing
extracellular H2O with 2H2O adversely affects both cell volume and growth rate oscillations and induces aberrant morphologies. Normal growth and cell
morphology are rescued by replacing 2H2O with H2O. Further studies revealed that the cell volume oscillates in the pollen tube apical region. These cell volume oscillations
were not from changes in cell shape at the tip and were detectable up to 30 μm distal to the tip (the longest length measured).
Cell volume in the apical region oscillates with the same frequency as growth rate oscillations but surprisingly the cycles
are phase-shifted by 180°. Raman microscopy yields evidence that hydrodynamic flow out of the apex may be part of the biomechanics
that drive cellular expansion. The combined results suggest that hydrodynamic loading/unloading in the apical region induces
cell volume oscillations and has a role in driving cell elongation and pollen tube growth. 相似文献
12.
No differences have been observed in vivo between Lycopersicum peruvianum compatible and incompatible pollen during activation and pollen tube emission and organization, that is until 4 h and 30 min after pollination. During pollen activation the main events are the setting free of rough endoplasmic reticulum (RER) cisterns which were stacked in the mature pollen, the increase in the number of polysomes, and a great activity of the dictyosomes. Immediately after germination of the vegetative nucleus and the generative cell move into the tube, the generative cell diviting to form the male gametes; the tube then becomes organized in four zones. This series of changes is similar to what has already been observed in vitro except that in vitro the generative cell remains undivided and the whole process from seeding to tube organization takes 3 h instead of 4 h and 30 min after pollination, as it does in vivo. Our findings are compatible with the main models of the tube inhibition mechanism proposed till now.Abbreviations RER
rough endoplasmic reticulum
- GC
generative cell
- VN
vegetative nucleus
- GP
germinative pore
Research performed under C.N.R. (Italian National Research Council) program Biology of Reproduction 相似文献
13.
Actin and pollen tube growth 总被引:24,自引:0,他引:24
Summary Actin microfilaments (MFs) are essential for the growth of the pollen tube. Although it is well known that MFs, together with myosin, deliver the vesicles required for cell elongation, it is becoming evident that the polymerization of new actin MFs, in a process that is independent of actomyosin-dependent vesicle translocation, is also necessary for cell elongation. Herein we review the recent literature that focuses on this subject, including brief discussions of the actin-binding proteins in pollen, and their possible role in regulating actin MF activity. We promote the view that polymerization of new actin MFs polarizes the cytoplasm at the apex of the tube. This process is regulated in part by the apical calcium gradient and by different actin-binding proteins. For example, profilin binds actin monomers and gives the cell control over the initiation of polymerization. A more recently discovered actin-binding protein, villin, stimulates the formation of unipolar bundles of MFs. Villin may also respond to the apical calcium gradient, fragmenting MFs, and thus locally facilitating actin remodeling. While much remains to be discovered, it is nevertheless apparent that actin MFs play a fundamental role in controlling apical cell growth in pollen tubes.Dedicated to Professor Brian E. S. Gunning on the occasion of his 65th birthday 相似文献
14.
N. J. Gawel C. D. Robacker 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1986,72(1):84-87
Summary All possible crosses among 5 strains of Gossypium hirsutum were made, and the pollen tubes were grown in vivo for 4 h before being fixed, stained and measured. Temperatures ranging from 18.5 to 40.0 °C were tested for pollen germination and pollen tube growth. The optimal temperature for pollen tube growth was 30.0 °C. Relative humidity levels of 0 to 100% were used as a pre-pollination treatment of the pollen. Significant differences among the mean pollen tube length of the strains occurred due to pollenXstyle interactions. The strains also differed in the number of styles which did not support pollen tube growth. These differences were also due to pollenXstyle interactions. Pollen and style strains could be ranked according to their relative contribution to pollen tube length.College of Agricultural Sciences Publication Number T-4-189 相似文献
15.
Pollen tube elongation in the pistil is a crucial step in the sexual reproduction of plants. Because the wall of the pollen tube tip is composed of a single layer of pectin and, unlike most other plant cell walls, does not contain cellulose or callose, pectin methylesterases (PMEs) likely play a central role in the pollen tube growth and determination of pollen tube morphology. Thus, the functional studies of pollen-specific PMEs, which are still in their infancy, are important for understanding the pollen development. We identified a new Arabidopsis pollen-specific PME, AtPPME1, characterized its native expression pattern, and used reverse genetics to demonstrate its involvement in determination of the shape of the pollen tube and the rate of its elongation. 相似文献
16.
Ovary signals for directional pollen tube growth 总被引:4,自引:0,他引:4
M. Herrero 《Sexual plant reproduction》2001,14(1-2):3-7
In angiosperms, the female gametophyte has a secluded life; it is protected by several concentric layers that envelop each
other. The embryo sac is surrounded by the nucellus, which in turn is wrapped by the integuments forming the ovule, which
is nested in the ovary. These wrappings are not hermetic, but contain little ”gates” the pollen tube must traverse on its
way towards the embryo sac. Information is emerging that shows that the ovary and ovule provide signals orienting and directimng
the pollen tube on the right course. There are three main bodies of evidence supporting this hypothesis. One relates to developmental
changes in the female tissues and how they affect pollen tube growth. The second refers to defective ovule mutants, which
induce defective pollen tube guidance. And the third relates to the possible molecules involved in this signalling. Here,
information gathered along these three main lines of evidence is reviewed. All converge to the conclusion that different checkpoints
exist all along the pollen tube pathway. These checkpoints provide active signalling that guides the pollen tube to its destination,
the embryo sac.
Received: 15 December 2000 / Accepted: 13 June 2001 相似文献
17.
Pollen tube dynamics following different competition regimes were studied in sweet cherry (Prunus avium L.). In the process from pollination to fertilization, a constant reduction in the number of pollen tubes that travel along the style is observed. There could be two main causes of this reduction. One is a physical or physiological constraint consisting of the progressive decrease in the reserves and space available for pollen tube growth along the transmitting tissue of the style, and the other is genetic interaction both among the male gametophytes and between the male gametophytes and the female tissues of the flower. To evaluate the roles that these two forces play in reducing the number of pollen tubes that travel along the style, pistils were subjected to various pollen competition regimes by applying different mixtures of live and dead pollen onto the stigmata. The results obtained were similar when the experiment was repeated with different genotypes over 2 years, both in the laboratory and in the field. The role of stylar constriction is important, but it is not the only cause of pollen tube attrition because with low pollen loads fewer pollen tubes reach the different parts of the style than could fit therein. The fact that under different pollen competition regimes the number of pollen tubes is reduced by the same proportion in each stylar level indicates that genetic interactions play an important role in the control of pollen tube attrition. 相似文献
18.
Phosphoinositides play important roles in eukaryotic cells, although they constitute a minor fraction of total cellular lipids. Specific kinases and phosphatases function on the regulation of phosphoinositide levels. Phosphatidylinositol 3-phosphate (PtdIns3P), a molecule of phosphoinositides regulates multiple aspects of plant growth and development. In this article, we introduce and discuss the kinases and phosphatases involved in PtdIns3P metabolism and their roles in pollen development and pollen tube growth in Arabidopsis. 相似文献
19.
The nucellar beak is a proboscis-like outgrowth of the nucellus at the micropylar end, being the obligatory path for the pollen tube entering the ovule. Among the few angiosperm families with nucellar beak, Cucurbitaceae is remarkable because the pollen tube may develop at least two types of growth within the nucellar beak: tubular and ampulliform. Wondering about the possibility that Cucurbitaceae ovules may express some histological variation that could be related to pollen tube growth within the nucellar beak, we performed a compared anatomical and histochemical study of the nucellar beak and the pollen tube growth of ten species of Cucurbitaceae. Results show that Cucurbitaceae ovules are diverse in size and proportions (of integuments, nucellar body, and nucellar beak), and they have at least four types of nucellar beak histology: pectic-tracked, secretory-like, amylaceous, and mixed. Amylaceous and mixed nucellar beaks are related to the ampulliform growth of the pollen tube, which could have appeared independently in most derived tribes of Cucurbitaceae, although information about nucellar beak structure in the basal tribes is still needed. In addition, the understanding of the relation between amylaceous nucellar beaks and the ampulliform growth of the pollen tube, whose function is still to be discovered, might open the possibility of a unique model of pollen tube-ovule co-evolution in angiosperms. 相似文献
20.
Gametophytic self-incompatibility inhibits pollen tube growth using different mechanisms 总被引:3,自引:0,他引:3
Self-incompatibility (SI) is one of the most important mechanisms used by plants to prevent self-pollination and consequently inbreeding. It is genetically controlled by the S-locus, which allows the recognition and rejection of ‘self’ (S-phenotypically identical) pollen. Gametophytically controlled SI (GSI) is the most widespread SI system. To date, only two forms have been elucidated in detail at the molecular level, revealing two different stigmatic S-genes. Here we summarize the evidence for the use of two different mechanisms to inhibit incompatible pollen tube growth. Because the limited data suggest the independent evolution of these two GSI systems, it would be interesting to explore other GSI systems to determine the extent of the mechanistic diversity. 相似文献