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.

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 Intracellular motility and the evolution of the actin cytoskeleton during development of the male gametophyte of wheat ( Triticum aestivum L.)

1997 ◽  
Vol 352 (1364) ◽  
pp. 1985-1993 ◽  
Author(s):  
J. Heslop-Harrison ◽  
Y. Heslop-Harrison
Keyword(s):  
Actin Cytoskeleton ◽  
Vegetative Cell ◽  
Male Gametophyte ◽  
Generative Cell ◽  
Triticum Aestivum L ◽  
Starch Accumulation ◽  
Vegetative Nucleus ◽  
Published Evidence ◽  
Main Period ◽  
Actin Mrna

The uniaperturate pollen of wheat is dispersed in a partially hydrated condition. Amyloplasts are concentrated in the apertural hemisphere where they surround the two sperms, while vigorously moving polysaccharide–containing wall precursor bodies (P–particles) together with the vegetative nucleus occupy the other. This disposition is the product of a post–meiotic developmental sequence apparently peculiar to the grasses. During vacuolation of the spore after release from the tetrad, the nucleus is displaced to the pole of the cell opposite the site of the germination aperture, already defined in the tetrad. Following pollen mitosis, the vegetative nucleus migrates along the wall of the vegetative cell towards the aperture, leaving the generative cell at the opposite pole isolated by a callose wall. As the vacuole is resorbed, the generative cell rounds up, loses its wall and follows the vegetative nucleus, passing along the wall of the vegetative cell towards the aperture where it eventually divides to produce the two sperms. Throughout this period of nucleus and cell manoeuvrings, minor inclusions of the vegetative cell cytoplasm, including mitochondria, lipid globuli and developing amyloplasts, move randomly. Coordinated vectorial movement begins after the main period of starch accumulation, when the amyloplasts migrate individually into the apertural hemisphere of the grain, a final redistribution betokening the attainment of germinability. In the present paper we correlate aspects of the evolution of the actin cytoskeleton with these events in the developing grain, and relate the observations to published evidence from another monocotyledonous species concerning the timing of the expression of actin genes during male gametophyte development, as revealed in the synthesis of actin mRNA.

Restoration of movement and apical growth in the angiosperm pollen tube following cytochalasin-induced paralysis

1991 ◽  
Vol 331 (1260) ◽  
pp. 225-235 ◽  
Keyword(s):  
Actin Cytoskeleton ◽  
Vegetative Cells ◽  
Cytoplasmic Inclusions ◽  
Essentially Normal ◽  
Narcissus Pseudonarcissus ◽  
Partial Dissociation ◽  
Actin Fibrils ◽  
Angiosperm Pollen ◽  
Generative Cells ◽  
Rapid Contraction

Cytochalasin D (CD) at 5 pg ml- 1 arrested growth and vectorial movement in pollen tubes of Narcissus pseudonarcissus and Endymion nonscriptus and caused the mainly longitudinally oriented actin fibrils in the vegetative cells to coalesce and form massive, more randomly oriented, cables. As extension growth was arrested, the tubes formed apical bulbs and abnormal wall thickenings. During recovery from a 10 min treatment period in E. nonscriptus , an essentially normal fibril system was reconstituted by partial dissociation of the thick cables formed during the exposure to CD. As this progressed movement was restored in the vegetative cells. Some 80 % of the blocked tubes initiated new growing points, either by producing randomly oriented swellings in sites where the wall was thinner, or by erosion and penetration of thicker zones. Contrary to expectation, the sites of the prospective growing points were not indicated in advance by any special disposition of the actin cytoskeleton. With the transition to cylindrical growth in the secondary tubes the standard stratification of the tube wall reappeared, with outer pectocellulosic and inner callosic layers. Normal movement pathways were established concomitantly, together with the apical zonation of organelles and other cytoplasmic inclusions characteristic of the extending tube. CD-treatment brought about rapid contraction of the vegetative nuclei with the loss of the elastic extensions of the nuclear envelopes. The extended form was resumed as the actin cytoskeleton was restored during recovery, and vegetative nuclei and generative cells moved into the secondary tubes where they continued to track the apex as in the normal tube.

scholarly journals Protein Analysis of Pollen Tubes after the Treatments of Membrane Trafficking Inhibitors Gains Insights on Molecular Mechanism Underlying Pollen Tube Polar Growth

2021 ◽  
Vol 40 (2) ◽  
pp. 205-222
Author(s):  
Monica Scali ◽  
Alessandra Moscatelli ◽  
Luca Bini ◽  
Elisabetta Onelli ◽  
Rita Vignani ◽  
...  
Keyword(s):  
Pollen Tube ◽  
Actin Cytoskeleton ◽  
Membrane Trafficking ◽  
Tip Growth ◽  
Male Gametophyte ◽  
Pollen Tubes ◽  
Structural Features ◽  
Two Dimensional Gel Electrophoresis ◽  
Depth Analysis

AbstractPollen tube elongation is characterized by a highly-polarized tip growth process dependent on an efficient vesicular transport system and largely mobilized by actin cytoskeleton. Pollen tubes are an ideal model system to study exocytosis, endocytosis, membrane recycling, and signaling network coordinating cellular processes, structural organization and vesicular trafficking activities required for tip growth. Proteomic analysis was applied to identifyNicotiana tabacumDifferentially Abundant Proteins (DAPs) after in vitro pollen tube treatment with membrane trafficking inhibitors Brefeldin A, Ikarugamycin and Wortmannin. Among roughly 360 proteins separated in two-dimensional gel electrophoresis, a total of 40 spots visibly changing between treated and control samples were identified by MALDI-TOF MS and LC–ESI–MS/MS analysis. The identified proteins were classified according to biological processes, and most proteins were related to pollen tube energy metabolism, including ammino acid synthesis and lipid metabolism, structural features of pollen tube growth as well modification and actin cytoskeleton organization, stress response, and protein degradation. In-depth analysis of proteins corresponding to energy-related pathways revealed the male gametophyte to be a reliable model of energy reservoir and dynamics.

scholarly journals Persistent directional growth capability in Arabidopsis thaliana pollen tubes after nuclear elimination from the apex

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Kazuki Motomura ◽  
Hidenori Takeuchi ◽  
Michitaka Notaguchi ◽  
Haruna Tsuchi ◽  
Atsushi Takeda ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Pollen Tube ◽  
Sperm Cell ◽  
Pollen Tubes ◽  
Vegetative Nucleus ◽  
Sperm Cells ◽  
Apical Region ◽  
Basal Region ◽  
Specific Expression ◽  
Directional Growth

AbstractDuring the double fertilization process, pollen tubes deliver two sperm cells to an ovule containing the female gametes. In the pollen tube, the vegetative nucleus and sperm cells move together to the apical region where the vegetative nucleus is thought to play a crucial role in controlling the direction and growth of the pollen tube. Here, we report the generation of pollen tubes in Arabidopsis thaliana whose vegetative nucleus and sperm cells are isolated and sealed by callose plugs in the basal region due to apical transport defects induced by mutations in the WPP domain-interacting tail-anchored proteins (WITs) and sperm cell-specific expression of a dominant mutant of the CALLOSE SYNTHASE 3 protein. Through pollen-tube guidance assays, we show that the physiologically anuclear mutant pollen tubes maintain the ability to grow and enter ovules. Our findings provide insight into the sperm cell delivery mechanism and illustrate the independence of the tip-localized vegetative nucleus from directional growth control of the pollen tube.

scholarly journals NETWORKED2‐Subfamily Proteins Regulate the Cortical Actin Cytoskeleton of Growing Pollen Tubes and Polarised Pollen Tube Growth

2021 ◽  
Author(s):  
Patrick Duckney ◽  
Johan T. Kroon ◽  
Martin R. Dixon ◽  
Timothy J. Hawkins ◽  
Michael J. Deeks ◽  
...  
Keyword(s):  
Pollen Tube ◽  
Actin Cytoskeleton ◽  
Pollen Tube Growth ◽  
Pollen Tubes ◽  
Tube Growth ◽  
Cortical Actin

The tricornered Gene, Which Is Required for the Integrity of Epidermal Cell Extensions, Encodes the Drosophila Nuclear DBF2-Related Kinase

Genetics ◽  
2000 ◽  
Vol 156 (4) ◽  
pp. 1817-1828 ◽  
Author(s):  
Wei Geng ◽  
Biao He ◽  
Mina Wang ◽  
Paul N Adler
Keyword(s):  
Actin Cytoskeleton ◽  
Actin Polymerization ◽  
Cell Structure ◽  
Cytochalasin D ◽  
Epidermal Cells ◽  
Sense Organs ◽  
Latrunculin A ◽  
Cellular Extensions ◽  
Cuticular Structures ◽  
Cuticular Surface

Abstract During their differentiation epidermal cells of Drosophila form a rich variety of polarized structures. These include the epidermal hairs that decorate much of the adult cuticular surface, the shafts of the bristle sense organs, the lateral extensions of the arista, and the larval denticles. These cuticular structures are produced by cytoskeletal-mediated outgrowths of epidermal cells. Mutations in the tricornered gene result in the splitting or branching of all of these structures. Thus, tricornered function appears to be important for maintaining the integrity of the outgrowths. tricornered mutations however do not have major effects on the growth or shape of these cellular extensions. Inhibiting actin polymerization in differentiating cells by cytochalasin D or latrunculin A treatment also induces the splitting of hairs and bristles, suggesting that the actin cytoskeleton might be a target of tricornered. However, the drugs also result in short, fat, and occasionally malformed hairs and bristles. The data suggest that the function of the actin cytoskeleton is important for maintaining the integrity of cellular extensions as well as their growth and shape. Thus, if tricornered causes the splitting of cellular extensions by interacting with the actin cytoskeleton it likely does so in a subtle way. Consistent with this possibility we found that a weak tricornered mutant is hypersensitive to cytochalasin D. We have cloned the tricornered gene and found that it encodes the Drosophila NDR kinase. This is a conserved ser/thr protein kinase found in Caenorhabditis elegans and humans that is related to a number of kinases that have been found to be important in controlling cell structure and proliferation.

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