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 A Tug-of-War Model Explains the Saltatory Sperm Cell Movement in Arabidopsis thaliana Pollen Tubes by Kinesins With Calponin Homology Domain

2021 ◽  
Vol 11 ◽  
Author(s):  
Saskia Schattner ◽  
Jan Schattner ◽  
Fabian Munder ◽  
Eva Höppe ◽  
Wilhelm J. Walter
Keyword(s):  
Arabidopsis Thaliana ◽  
Pollen Tube ◽  
Sperm Cell ◽  
Cell Movement ◽  
Pollen Tubes ◽  
Vegetative Nucleus ◽  
Sperm Cells ◽  
Calponin Homology Domain ◽  
Calponin Homology ◽  
Actin Cables

Upon pollination, two sperm cells are transported inside the growing pollen tube toward the apex. One sperm cell fertilizes the egg cell to form the zygote, while the other fuses with the two polar nuclei to form the triploid endosperm. In Arabidopsis thaliana, the transport of the two sperm cells is characterized by sequential forward and backward movements with intermediate pauses. Until now, it is under debate which components of the plant cytoskeleton govern this mechanism. The sperm cells are interconnected and linked to the vegetative nucleus via a cytoplasmic projection, thus forming the male germ unit. This led to the common hypothesis that the vegetative nucleus is actively transported via myosin motors along actin cables while pulling along the sperm cells as passive cargo. In this study, however, we show that upon occasional germ unit disassembly, the sperm cells are transported independently and still follow the same bidirectional movement pattern. Moreover, we found that the net movement of sperm cells results from a combination of both longer and faster runs toward the pollen tube apex. We propose that the observed saltatory movement can be explained by the function of kinesins with calponin homology domain (KCH). This subgroup of the kinesin-14 family actively links actin filaments and microtubules. Based on KCH's specific properties derived from in vitro experiments, we built a tug-of-war model that could reproduce the characteristic sperm cell movement in pollen tubes.

The nuclear envelope protein KAKU4 determines the migration order of the vegetative nucleus and sperm cells in pollen tubes

2020 ◽  
Vol 71 (20) ◽  
pp. 6273-6281 ◽  
Author(s):  
Chieko Goto ◽  
Kentaro Tamura ◽  
Satsuki Nishimaki ◽  
Daisuke Maruyama ◽  
Ikuko Hara-Nishimura
Keyword(s):  
Sperm Cell ◽  
Pollen Grains ◽  
Nuclear Lamina ◽  
Pollen Tubes ◽  
Pollen Grain ◽  
Vegetative Nucleus ◽  
Sperm Cells ◽  
Wild Type ◽  
Cell Nuclei ◽  
In The Wild

Abstract A putative component protein of the nuclear lamina, KAKU4, modulates nuclear morphology in Arabidopsis thaliana seedlings, but its physiological significance is unknown. KAKU4 was highly expressed in mature pollen grains, each of which has a vegetative cell and two sperm cells. KAKU4 protein was highly abundant on the envelopes of vegetative nuclei and less abundant on the envelopes of sperm cell nuclei in pollen grains and elongating pollen tubes. Vegetative nuclei are irregularly shaped in wild-type pollen. However, KAKU4 deficiency caused them to become more spherical. After a pollen grain germinates, the vegetative nuclei and sperm cells enter and move along the pollen tube. In the wild type, the vegetative nucleus preceded the sperm cell nuclei in >90% of the pollen tubes, whereas, in kaku4 mutants, the vegetative nucleus preceded the sperm cell nuclei in only about half of the pollen tubes. kaku4 pollen was less competitive for fertilization than wild-type pollen after pollination. These results led us to hypothesize that the nuclear shape in vegetative cells of pollen grains affects the orderly migration of the vegetative nucleus and sperm cells in pollen tubes.

scholarly journals KAKU4-mediated deformation of the vegetative nucleus controls its precedent migration over sperm cells in pollen tubes

2019 ◽  
Author(s):  
Chieko Goto ◽  
Kentaro Tamura ◽  
Satsuki Nishimaki ◽  
Naoki Yanagisawa ◽  
Kumi Matsuura-Tokita ◽  
...  
Keyword(s):  
Competitive Ability ◽  
Pollen Grains ◽  
Nuclear Lamina ◽  
Pollen Tubes ◽  
Vegetative Nucleus ◽  
Sperm Cells ◽  
Wild Type ◽  
Cell Nuclei ◽  
In The Wild ◽  
Dense Accumulation

AbstractA putative nuclear lamina protein, KAKU4, modulates nuclear morphology in Arabidopsis thaliana seedlings but its physiological significance is unknown. KAKU4 was strongly expressed in mature pollen grains, each of which has a vegetative cell and two sperm cells. KAKU4 protein was highly abundant on the envelopes of vegetative nuclei (VNs) and less abundant on the envelopes of sperm cell nuclei (SCNs) in pollen grains and elongating pollen tubes. VN is irregularly shaped in wild-type pollen. However, KAKU4 deficiency caused it to become more spherical. These results suggest that the dense accumulation of KAKU4 is responsible for the irregular shape of the VNs. After a pollen grain germinates, the VN and SCNs migrate to the tip of the pollen tube. In the wild type, the VN preceded the SCNs in 91–93% of the pollen tubes, whereas in kaku4 mutants, the VN trailed the SCNs in 39–58% of the pollen tubes. kaku4 pollen was less competitive than wild-type pollen after pollination, although it had an ability to fertilize. Taken together, our results suggest that controlling the nuclear shape in vegetative cells of pollen grains by KAKU4 ensures the orderly migration of the VN and sperm cells in pollen tubes.HighlightThe nuclear envelope protein KAKU4 is involved in controlling the migration order of vegetative nuclei and sperm cells in pollen tubes, affecting the competitive ability of pollen for fertilization.

Dynamics of the apical vesicle accumulation and the rate of growth are related in individual pollen tubes

2001 ◽  
Vol 114 (14) ◽  
pp. 2685-2695 ◽  
Author(s):  
R. M. Parton ◽  
S. Fischer-Parton ◽  
M. K. Watahiki ◽  
A. J. Trewavas
Keyword(s):  
Growth Rate ◽  
Plasma Membrane ◽  
Pollen Tube ◽  
Staining Pattern ◽  
Periodic Oscillation ◽  
Quantitative Relationship ◽  
Pollen Tubes ◽  
Apical Region ◽  
Secretory Vesicles ◽  
Animal Cells

Regulated secretory vesicle delivery, vesicle fusion and rapid membrane recycling are all contentious issues with respect to tip growth in plant, fungal and animal cells. To examine the organisation and dynamics of membrane movements at the growing pollen tube apex and address the question of their relationship to growth, we have used the membrane stain FM4-64 both as a structural marker and as a quantitative assay. Labelling of living Lilium Longiflorum pollen tubes by FM4-64 resulted in a distinct staining pattern in the tube apex, which corresponds spatially to the previously identified cone-shaped `apical clear zone' containing secretory vesicles. Dye uptake could be inhibited by sodium azide and followed a strict temporal sequence from the plasma membrane to a population of small (1-2 μm diameter) discrete internal structures, with subsequent appearance of dye in the apical region and ultimately in vacuolar membranes. Washout of the dye rapidly removed the plasma membrane staining, which was followed by a gradual decline in the apical fluorescence over more than an hour. Injected aqueous FM4-64 solution showed a relatively even distribution within the pollen tube. Association of FM4-64 with apical secretory vesicles was supported by the effects of the inhibitors Brefeldin-A and Cytochalasin-D, which are known to affect the localisation and number of such vesicles, on the FM4-64 staining pattern. Examination of the dynamics of FM4-64 labelling in the pollen tube tip by time-lapse observation, supported by fluorescence-recovery-after-photobleaching (FRAP) analysis, suggested the possibility of distinct pathways of bulk membrane movement both towards and, significantly, away from the apex. Quantitative analysis of FM4-64 distribution in the apex revealed that fluctuations in fluorescence 5 to 10 μm subapically, and to a lesser extent the apical 3 μm, could be related to the periodic oscillation in pollen tube growth rate. This data reveals a quantitative relationship between FM4-64 staining and growth rate within an individual tube.

scholarly journals Polyspermy Block in the Central Cell During Double Fertilization of Arabidopsis thaliana

2021 ◽  
Vol 11 ◽  
Author(s):  
Shiori Nagahara ◽  
Hidenori Takeuchi ◽  
Tetsuya Higashiyama
Keyword(s):  
Arabidopsis Thaliana ◽  
Sperm Cell ◽  
Central Cell ◽  
Egg Cell ◽  
Sperm Cells ◽  
Potential Contribution ◽  
Double Fertilization ◽  
Male Gametes ◽  
One To One ◽  
The One

During double fertilization in angiosperms, two male gametes (sperm cells), are released from a pollen tube into the receptive region between two female gametes; the egg cell and the central cell of the ovule. The sperm cells fertilize the egg cell and the central cell in a one-to-one manner to yield a zygote and an endosperm, respectively. The one-to-one distribution of the sperm cells to the two female gametes is strictly regulated, possibly via communication among the four gametes. Polyspermy block is the mechanism by which fertilized female gametes prevent fertilization by a secondary sperm cell, and has been suggested to operate in the egg cell rather than the central cell. However, whether the central cell also has the ability to avoid polyspermy during double fertilization remains unclear. Here, we assessed the one-to-one fertilization mechanism of the central cell by laser irradiation of the female gametes and live cell imaging of the fertilization process in Arabidopsis thaliana. We successfully disrupted an egg cell within the ovules by irradiation using a femtosecond pulse laser. In the egg-disrupted ovules, the central cell predominantly showed single fertilization by one sperm cell, suggesting that neither the egg cell nor its fusion with one sperm cell is necessary for one-to-one fertilization (i.e., monospermy) of the central cell. In addition, using tetraspore mutants possessing multiple sperm cell pairs in one pollen, we demonstrated that normal double fertilization was observed even when excess sperm cells were released into the receptive region between the female gametes. In ovules accepting four sperm cells, the egg cell never fused with more than one sperm cell, whereas half of the central cells fused with more than one sperm cell (i.e., polyspermy) even 1 h later. Our results suggest that the central cell can block polyspermy during double fertilization, although the central cell is more permissive to polyspermy than the egg cell. The potential contribution of polyspermy block by the central cell is discussed in terms of how it is involved in the one-to-one distribution of the sperm cells to two distinct female gametes.

Migration of sperm cells during pollen tube elongation in Arabidopsis thaliana: behavior during transport, maturation and upon dissociation of male germ unit associations

Planta ◽  
2010 ◽  
Vol 233 (2) ◽  
pp. 325-332 ◽  
Author(s):  
Lili Ge ◽  
Xiaoping Gou ◽  
Tong Yuan ◽  
Greg W. Strout ◽  
Jin Nakashima ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Pollen Tube ◽  
Sperm Cells ◽  
Male Germ Unit ◽  
Pollen Tube Elongation

scholarly journals The Arabidopsis thaliana Class II Formin FH13 Modulates Pollen Tube Growth

2021 ◽  
Vol 12 ◽  
Author(s):  
Eva Kollárová ◽  
Anežka Baquero Forero ◽  
Fatima Cvrčková
Keyword(s):  
Arabidopsis Thaliana ◽  
Pollen Tube ◽  
Pollen Tube Growth ◽  
Tip Growth ◽  
Pollen Tubes ◽  
Class Ii ◽  
Membrane Dynamics ◽  
Tube Growth ◽  
Class I ◽  
Pollen Tube Elongation

Formins are a large, evolutionarily conserved family of actin-nucleating proteins with additional roles in regulating microfilament, microtubule, and membrane dynamics. Angiosperm formins, expressed in both sporophytic and gametophytic tissues, can be divided into two subfamilies, Class I and Class II, each often exhibiting characteristic domain organization. Gametophytically expressed Class I formins have been documented to mediate plasma membrane-based actin assembly in pollen grains and pollen tubes, contributing to proper pollen germination and pollen tube tip growth, and a rice Class II formin, FH5/RMD, has been proposed to act as a positive regulator of pollen tube growth based on mutant phenotype and overexpression data. Here we report functional characterization of the Arabidopsis thaliana pollen-expressed typical Class II formin FH13 (At5g58160). Consistent with published transcriptome data, live-cell imaging in transgenic plants expressing fluorescent protein-tagged FH13 under the control of the FH13 promoter revealed expression in pollen and pollen tubes with non-homogeneous signal distribution in pollen tube cytoplasm, suggesting that this formin functions in the male gametophyte. Surprisingly, fh13 loss of function mutations do not affect plant fertility but result in stimulation of in vitro pollen tube growth, while tagged FH13 overexpression inhibits pollen tube elongation. Pollen tubes of mutants expressing a fluorescent actin marker exhibited possible minor alterations of actin organization. Our results thus indicate that FH13 controls or limits pollen tube growth, or, more generally, that typical Class II formins should be understood as modulators of pollen tube elongation rather than merely components of the molecular apparatus executing tip growth.

scholarly journals Intercellular communication in Arabidopsis thaliana pollen discovered via AHG3 transcript movement from the vegetative cell to sperm

2015 ◽  
Vol 112 (43) ◽  
pp. 13378-13383 ◽  
Author(s):  
Hua Jiang ◽  
Jun Yi ◽  
Leonor C. Boavida ◽  
Yuan Chen ◽  
Jörg D. Becker ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Pollen Tube ◽  
Intercellular Communication ◽  
Protein Phosphatase ◽  
Pollen Tube Growth ◽  
Vegetative Cell ◽  
Male Gametophyte ◽  
Pollen Grain ◽  
Sperm Cells ◽  
Coding Region

An Arabidopsis pollen grain (male gametophyte) consists of three cells: the vegetative cell, which forms the pollen tube, and two sperm cells enclosed within the vegetative cell. It is still unclear if there is intercellular communication between the vegetative cell and the sperm cells. Here we show that ABA-hypersensitive germination3 (AHG3), encoding a protein phosphatase, is specifically transcribed in the vegetative cell but predominantly translated in sperm cells. We used a series of deletion constructs and promoter exchanges to document transport of AHG3 transcripts from the vegetative cell to sperm and showed that their transport requires sequences in both the 5′ UTR and the coding region. Thus, in addition its known role in transporting sperm during pollen tube growth, the vegetative cell also contributes transcripts to the sperm cells.

Identification and localization of three classes of myosins in pollen tubes of Lilium longiflorum and Nicotiana alata

1995 ◽  
Vol 108 (7) ◽  
pp. 2549-2563
Author(s):  
D.D. Miller ◽  
S.P. Scordilis ◽  
P.K. Hepler
Keyword(s):  
Pollen Tube ◽  
Myosin Ii ◽  
Generative Cell ◽  
Freeze Substitution ◽  
Lilium Longiflorum ◽  
Pollen Tubes ◽  
Vegetative Nucleus ◽  
Nicotiana Alata ◽  
Myosin V ◽  
Myosin I

The presence and localization of actin and myosin have been examined in pollen tubes of Lilium longiflorum and Nicotiana alata. Immunoblot analysis of pollen tube extracts with antibodies to actin, myosins IA and IB, myosin II, and myosin V reveals the presence of these contractile proteins. Immunofluorescence microscopy using various methods to preserve the pollen tubes; chemical fixation, rapid freeze fixation and freeze substitution (RF-FS) followed by rehydration or by embeddment in a methacrylate mixture, was performed to optimize preservation. Immunocytochemistry reaffirmed that actin is localized longitudinally in the active streaming lanes and near the cortical surface of the pollen tube. Myosin I was localized to the plasma membrane, larger organelles, the surface of the generative cell and the vegetative nucleus, whereas, myosin V was found in the vegetative cytoplasm in a punctate fashion representing smaller organelles. Myosin II subfragment 1 and light meromyosin were localized in a punctate fashion on the larger organelles throughout the vegetative cytoplasm. In addition, isolated generative cells and vegetative nuclei labeled only with the myosin I antibody. Competition studies indicated the specificity of the heterologous antibodies utilized in this study suggesting the presence of three classes of myosins in pollen. These results lead to the following hypothesis: Myosin I may move the generative cell and vegetative nucleus unidirectionally through the pollen tube to the tip, while myosin V moves the smaller organelles and myosins I and II move the larger organelles (bidirectionally) that are involved in growth.

Sign in / Sign up

Export Citation Format

Share Document