Sites of Origin of the Peripheral Microtubule System of the Vegetative Cell of the Angiosperm Pollen Tube

1988 ◽  
Vol 62 (5) ◽  
pp. 455-461 ◽  
Author(s):  
J. HESLOP-HARRISON ◽  
Y. HESLOP-HARRISON
Keyword(s):  
Pollen Tube ◽  
Vegetative Cell ◽  
Angiosperm Pollen

Conformation and movement of the vegetative nucleus of the angiosperm pollen tube: association with the actin cytoskeleton

1989 ◽  
Vol 93 (2) ◽  
pp. 299-308
Author(s):  
J. HESLOP-HARRISON ◽  
Y. HESLOP-HARRISON
Keyword(s):  
Pollen Tube ◽  
Actin Cytoskeleton ◽  
Nuclear Envelope ◽  
Vegetative Cell ◽  
Cytochalasin D ◽  
Vegetative Nucleus ◽  
Continuous Change ◽  
Cytoplasmic Bodies ◽  
Angiosperm Pollen ◽  
Rapid Contraction

Actin is present in the cytoplasm of the vegetative cell of angiosperm pollens in numerous fusiform, spiculate or toroidal bodies, and also as a sheath enveloping the vegetative nucleus. During activation following hydration, the compact cytoplasmic bodies are translated into skeins of extended fibrils, and circulatory movements begin in the cytoplasm. Throughout this period the vegetative nucleus, with fibrillar actin now associated with the surface, undergoes a continuous change of shape. In the extending tube following germination the actin cytoskeleton consists of numerous mainly longitudinally oriented fibrils. After entry into the tube the vegetative nucleus remains associated with the fibrils, usually extending greatly in length and developing attenuated, often pointed extensions. The observed conformations, which change continuously, suggest that varying local tensions are applied to the vegetative nucleus during passage through the tube. Cytochalasin D breaks up the actin fibril system and brings about a rapid contraction of the nucleus, at the same time eliminating the elastic extensions of the nuclear envelope. Nuclei isolated physically from unfixed tubes also contract in length as the fibrillar components of the cytoskeleton are detached. These findings indicate that the movement of the vegetative nucleus depends on local associations of the nuclear envelope with the actin cytoskeleton of the vegetative cell.

Dynamic aspects of apical zonation in the angiosperm pollen tube

1990 ◽  
Vol 3 (3) ◽  
Author(s):  
J. Heslop-Harrison ◽  
Y. Heslop-Harrison
Keyword(s):  
Pollen Tube ◽  
Angiosperm Pollen

Actin During Pollen Germination

1986 ◽  
Vol 86 (1) ◽  
pp. 1-8
Author(s):  
J. HESLOP-HARRISON ◽  
Y. HESLOP-HARRISON ◽  
M. CRESTI ◽  
A. TIEZZI ◽  
F. CIAMPOLINI
Keyword(s):  
Medium Release ◽  
Pollen Tube ◽  
Vegetative Cell ◽  
Pollen Germination ◽  
Pollen Grain ◽  
Actin Microfilaments ◽  
Vegetative Cells ◽  
Stage Of Development ◽  
Angiosperm Species

The cytoplasm of the vegetative cell of the ungerminated pollen grain of Endymton non-scriplus and other angiosperm species contains numerous fusiform bodies sometimes exceeding 15μm in length and 2.5 μm in width, which bind fluorescent-labelled phalloidin and are likely therefore to constitute a storage form of actin. The bodies are dispersed during the activation of the pollen, being replaced by aggregates of slender phalloidin-binding fibrils, which converge towards the germination apertures and are present in the emerging pollen tube. The storage bodies appear to be homologous with crystalline-fibrillar structures, shown in an earlier paper to be abundantly present in the vegetative cells of Nicotiana pollen. These are composed of massive aggregates of linearly disposed units with individual widths of 4–7 nm, probably to be interpreted as actin microfilaments. Vegetative-cell protoplasts from mature but ungerminated pollen disrupted in osmotically balancing medium release extended phalloidin-binding fibrils of a kind not observed in the intact grain. It is suggested that these are derived by the rapid dissociation of the compact actin storage bodies present in the vegetative cell at this stage of development.

Cytoskeletal Elements, Cell Shaping and Movement in the Angiosperm Pollen Tube

1988 ◽  
Vol 91 (1) ◽  
pp. 49-60 ◽  
Author(s):  
J. HESLOP-HARRISON ◽  
Y. HESLOP-HARRISON ◽  
M. CRESTI ◽  
A. TIEZZI ◽  
A. MOSCATELLI
Keyword(s):  
Pollen Tube ◽  
Shape Change ◽  
Generative Cell ◽  
Vegetative Nucleus ◽  
Microtubule Cytoskeleton ◽  
Tube Shape ◽  
Galanthus Nivalis ◽  
Angiosperm Pollen ◽  
Cytoskeletal Elements ◽  
Generative Cells

The ellipsoidal generative cell of the pollen grain of Endymion nonscriptus usually elongates further following germination and entry into the tube, producing attenuated extensions the forward one of which may reach into the vicinity of the vegetative nucleus. This shape change is accompanied by the stretching of the microtubule cytoskeleton of the cell, identified in the present work by immunofluorescence using monoclonal antibodies to tubulin. Complementary observations of living generative cells of Iris pseudacorus showed that they undergo slow undulatory movements accompanied by variation in shape and length during passage through the tube. Such changes must presumably be accompanied by modifications of the microtubule cytoskeleton. Colchicine at 1 mM eliminated microtubules from tubes and most generative cells of E. nonscriptus, but did not radically affect pollen-tube shape or extension growth, nor arrest the movements of the vegetative nucleus and generative cell into and through the tube. Generative cells in colchicinetreated pollen of Galanthus nivalis rounded up and failed to undergo the usual changes in shape during passage through the tube. Secondary consequences were changes in precedence in movement through the tube, and a greater dispersal along its length. On the assumption that no other cytoskeletal elements remain to be discovered, it seems likely that microfilaments rather than microtubules provide the motive force for movement in the tube, although the latter are involved in shaping the generative cell and adapting it to its passage.

scholarly journals Actin Bundles in The Pollen Tube

2018 ◽  
Vol 19 (12) ◽  
pp. 3710 ◽  
Author(s):  
Shujuan Zhang ◽  
Chunbo Wang ◽  
Min Xie ◽  
Jinyu Liu ◽  
Zhe Kong ◽  
...  
Keyword(s):  
Pollen Tube ◽  
Tip Growth ◽  
Imaging Techniques ◽  
Embryo Sac ◽  
Pollen Tubes ◽  
Growth Strategy ◽  
Regulation Mechanism ◽  
Actin Bundles ◽  
Angiosperm Pollen ◽  
Plant Pollen

The angiosperm pollen tube delivers two sperm cells into the embryo sac through a unique growth strategy, named tip growth, to accomplish fertilization. A great deal of experiments have demonstrated that actin bundles play a pivotal role in pollen tube tip growth. There are two distinct actin bundle populations in pollen tubes: the long, rather thick actin bundles in the shank and the short, highly dynamic bundles near the apex. With the development of imaging techniques over the last decade, great breakthroughs have been made in understanding the function of actin bundles in pollen tubes, especially short subapical actin bundles. Here, we tried to draw an overall picture of the architecture, functions and underlying regulation mechanism of actin bundles in plant pollen tubes.

scholarly journals Myosin associated with the surfaces of organelles, vegetative nuclei and generative cells in angiosperm pollen grains and tubes

1989 ◽  
Vol 94 (2) ◽  
pp. 319-325
Author(s):  
J. HESLOP-HARRISON ◽  
Y. HESLOP-HARRISON
Keyword(s):  
Pollen Tube ◽  
Pollen Grains ◽  
Giant Cells ◽  
Pollen Tubes ◽  
Microfilament Bundles ◽  
Hyacinthus Orientalis ◽  
Actin Fibrils ◽  
Angiosperm Pollen ◽  
Muscle Myosin ◽  
Generative Cells

Myosin, detected by immunofluorescence using an antibody to bovine skeletal and smooth muscle myosin, has been localised on individual identifiable organelles from the grasses Alopecurus pratensis and Secale cereale, and on the surfaces of vegetative nuclei and generative cells from pollen and pollen tubes of Hyacinthus orientalis and Helleborus foetidus. Taken in conjunction with recent evidence showing that the growing pollen tube contains an actin cytoskeleton consisting of numerous mainly longitudinally oriented microfilament bundles, and that isolated pollen-tube organelles show ATP-dependent movement along the actin bundles of the giant cells of the characeous algae, this finding suggests that an actomyosin motility system is present in pollen tubes, and indicates that the movements of the different classes of inclusions are driven by interaction of the surface myosin with the actin fibrils at the zones of contact.

scholarly journals Proteomic Analysis of Generative and Vegetative Nuclei Reveals Molecular Characteristics of Pollen Cell Differentiation in Lily

2021 ◽  
Vol 12 ◽  
Author(s):  
Chen You ◽  
YuPing Zhang ◽  
ShaoYu Yang ◽  
Xu Wang ◽  
Wen Yao ◽  
...  
Keyword(s):  
Cell Differentiation ◽  
Pollen Tube ◽  
Cell Fate ◽  
Vegetative Cell ◽  
Generative Cell ◽  
Histone Variants ◽  
Molecular Characteristics ◽  
Nuclear Pore ◽  
Cell Nuclei ◽  
Pollen Cell

In plants, the cell fates of a vegetative cell (VC) and generative cell (GC) are determined after the asymmetric division of the haploid microspore. The VC exits the cell cycle and grows a pollen tube, while the GC undergoes further mitosis to produce two sperm cells for double fertilization. However, our understanding of the mechanisms underlying their fate differentiation remains limited. One major advantage of the nuclear proteome analysis is that it is the only method currently able to uncover the systemic differences between VC and GC due to GC being engulfed within the cytoplasm of VC, limiting the use of transcriptome. Here, we obtained pure preparations of the vegetative cell nuclei (VNs) and generative cell nuclei (GNs) from germinating lily pollens. Utilizing these high-purity VNs and GNs, we compared the differential nucleoproteins between them using state-of-the-art quantitative proteomic techniques. We identified 720 different amount proteins (DAPs) and grouped the results in 11 fate differentiation categories. Among them, we identified 29 transcription factors (TFs) and 10 cell fate determinants. Significant differences were found in the molecular activities of vegetative and reproductive nuclei. The TFs in VN mainly participate in pollen tube development. In comparison, the TFs in GN are mainly involved in cell differentiation and male gametogenesis. The identified novel TFs may play an important role in cell fate differentiation. Our data also indicate differences in nuclear pore complexes and epigenetic modifications: more nucleoporins synthesized in VN; more histone variants and chaperones; and structural maintenance of chromosome (SMC) proteins, chromatin remodelers, and DNA methylation-related proteins expressed in GN. The VC has active macromolecular metabolism and mRNA processing, while GC has active nucleic acid metabolism and translation. Moreover, the members of unfolded protein response (UPR) and programmed cell death accumulate in VN, and DNA damage repair is active in GN. Differences in the stress response of DAPs in VN vs. GN were also found. This study provides a further understanding of pollen cell differentiation mechanisms and also a sound basis for future studies of the molecular mechanisms behind cell fate differentiation.

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