scholarly journals Feeling the force: how pollen tubes deal with obstacles

2018 ◽  
Author(s):  
Jan T. Burri ◽  
Hannes Vogler ◽  
Nino F. Läubli ◽  
Chengzhi Hu ◽  
Ueli Grossniklaus ◽  
...  
Keyword(s):  
Pollen Tube ◽  
Mechanical Stress ◽  
Turgor Pressure ◽  
Lilium Longiflorum ◽  
Pollen Tubes ◽  
Cellular Growth ◽  
Force Perception ◽  
Male Gametes ◽  
Ideal System ◽  
Growth Adjustment

HighlightPollen tubes literally feel their way through their environment to avoid obstacles as they deliver male gametes to the ovule. We measured their force sensitivity to understand this remarkable behavior.AbstractPhysical forces are involved in the regulation of plant development and morphogenesis by translating mechanical stress into the modification of physiological processes, which, in turn, can affect cellular growth. Pollen tubes are tip-growing cells that provide an ideal system to study processes induced by exposure to mechanical stress. We combined a lab-on-a-chip device with cellular force microscopy to mimic and quantify the forces that are involved in pollen tube navigation upon confronting mechanical obstacles. Several stages of obstacle avoidance were identified, including force perception, growth adjustment, and penetration. We have experimentally determined the perceptive force, which is the force threshold at which the pollen tube senses the obstacle, for Lilium longiflorum and Arabidopsis thaliana. In addition, we provide evidence that pollen tubes are capable of penetrating narrow gaps by increasing turgor pressure. Taken together, our data indicate that pollen tubes sense physical barriers and actively adjust their growth behavior to overcome them.

scholarly journals Comparative analyses of angiosperm secretomes identify apoplastic pollen tube functions and novel secreted peptides

2020 ◽  
Author(s):  
María Flores-Tornero ◽  
Lele Wang ◽  
David Potěšil ◽  
Said Hafidh ◽  
Frank Vogler ◽  
...  
Keyword(s):  
Cell Wall ◽  
Pollen Tube ◽  
Turgor Pressure ◽  
Pollen Grains ◽  
Pollen Tubes ◽  
Secreted Proteins ◽  
Reproductive Tissues ◽  
Small Proteins ◽  
Secreted Peptides

Abstract Key message Analyses of secretomes of in vitro grown pollen tubes from Amborella, maize and tobacco identified many components of processes associated with the cell wall, signaling and metabolism as well as novel small secreted peptides. Abstract Flowering plants (angiosperms) generate pollen grains that germinate on the stigma and produce tubes to transport their sperm cells cargo deep into the maternal reproductive tissues toward the ovules for a double fertilization process. During their journey, pollen tubes secrete many proteins (secreted proteome or secretome) required, for example, for communication with the maternal reproductive tissues, to build a solid own cell wall that withstands their high turgor pressure while softening simultaneously maternal cell wall tissue. The composition and species specificity or family specificity of the pollen tube secretome is poorly understood. Here, we provide a suitable method to obtain the pollen tube secretome from in vitro grown pollen tubes of the basal angiosperm Amborella trichopoda (Amborella) and the Poaceae model maize. The previously published secretome of tobacco pollen tubes was used as an example of eudicotyledonous plants in this comparative study. The secretome of the three species is each strongly different compared to the respective protein composition of pollen grains and tubes. In Amborella and maize, about 40% proteins are secreted by the conventional “classic” pathway and 30% by unconventional pathways. The latter pathway is expanded in tobacco. Proteins enriched in the secretome are especially involved in functions associated with the cell wall, cell surface, energy and lipid metabolism, proteolysis and redox processes. Expansins, pectin methylesterase inhibitors and RALFs are enriched in maize, while tobacco secretes many proteins involved, for example, in proteolysis and signaling. While the majority of proteins detected in the secretome occur also in pollen grains and pollen tubes, and correlate in the number of mapped peptides with relative gene expression levels, some novel secreted small proteins were identified. Moreover, the identification of secreted proteins containing pro-peptides indicates that these are processed in the apoplast. In conclusion, we provide a proteome resource from three distinct angiosperm clades that can be utilized among others to study the localization, abundance and processing of known secreted proteins and help to identify novel pollen tube secreted proteins for functional studies.

Functional genomics of pollen tube–pistil interactions in Arabidopsis

2010 ◽  
Vol 38 (2) ◽  
pp. 593-597 ◽  
Author(s):  
Ravishankar Palanivelu ◽  
Mark A. Johnson
Keyword(s):  
Pollen Tube ◽  
Regulatory Networks ◽  
Genomic Analysis ◽  
Pollen Tubes ◽  
Cellular Growth ◽  
Functional Genomic ◽  
Reverse Genetic ◽  
Guidance Cues ◽  
Functional Genomic Analysis

The pollen tube represents an attractive model system for functional genomic analysis of the cell–cell interactions that mediate guided cellular growth. The pollen tube extends through pistil tissues and responds to guidance cues that direct the tube towards an ovule, where it releases sperm for fertilization. Pollen is readily isolated from anthers, where it is produced, and can be induced to produce a tube in vitro. Interestingly, pollen tube growth is significantly enhanced in pistils, and pollen tubes are rendered competent to respond to guidance cues after growth in a pistil. This potentiation of the pollen tube by the pistil suggested that pollen tubes alter their gene-expression programme in response to their environment. Recently, the transcriptomes of pollen tubes grown in vitro or through pistil tissues were determined. Significant changes in the transcriptome were found to accompany growth in vitro and through the pistil tissues. Reverse genetic analysis of pollen-tube-induced genes identified a new set of factors critical for pollen tube extension and navigation of the pistil environment. Recent advances reviewed in the present paper suggest that functional genomic analysis of pollen tubes has the potential to uncover the regulatory networks that shape the genetic architecture of the pollen tube as it responds to migratory cues produced by the pistil.

scholarly journals pH gradients are not associated with tip growth in pollen tubes of Lilium longiflorum

1997 ◽  
Vol 110 (15) ◽  
pp. 1729-1740 ◽  
Author(s):  
M.D. Fricker ◽  
N.S. White ◽  
G. Obermeyer
Keyword(s):  
Pollen Tube ◽  
Tip Growth ◽  
Lilium Longiflorum ◽  
Pollen Tubes ◽  
Tube Growth ◽  
Cytoplasmic Ph ◽  
Clear Zone ◽  
External Application ◽  
Ph Gradients ◽  
External Ph

The cytoplasmic pH of growing pollen tubes of Lilium longiflorum Thunb. was measured using the pH-sensitive fluorescent dye 2′,7′-bis-(carboxyethyl)-5(6′)-carboxyfl uorescein and confocal fluorescence ratio imaging. The average cytoplasmic pH in the clear zone of the pollen tube tip was pH 7.11, and no consistent pH gradients were detected in the clear zone, averaging around -1.00 milli pH unit microm(−1), or along the first 50 microm of the tube (3.62 milli pH units microm[-1]). In addition, no correlation was observed between the absolute tip cytoplasmic pH or the pH gradient and the pollen tube growth rates. Shifts of external pH to more acidic pH values (pH 4.5) caused a relatively small acidification by 0.18 pH units, whereas a more alkaline external pH >7.0 caused a dramatic increase in cytoplasmic pH and growth stopped immediately. Stimulation of the plasma membrane H+-ATPase by fusicoccin, resulted in an increase of tube growth but no change in cytoplasmic pH. On the other hand, vanadate (250–500 microM), a putative inhibitor of the pump, stopped tube growth and a slight cytoplasmic alkalinisation of 0.1 pH units was observed. Vanadate also arrested fusicoccin-stimulated growth and stimulated an increased alkalinisation of around 0.2 pH units. External application of CaCl2 (10 mM) caused a small acidification of less than 0.1 pH units in the clear zone, whilst LaCl3 (250 microM) caused slight and rather variable perturbations in cytoplasmic pH of no more than 0.1 pH units. Both treatments stopped growth. It was inferred from these data that tip-acid cytoplasmic pH gradients do not play a central role in the organisation or maintenance of pollen tube tip growth.

scholarly journals Autoradiographs of Pollen Tube Nuclei with Calcium-45

1959 ◽  
Vol 6 (3) ◽  
pp. 339-342 ◽  
Author(s):  
Dale Steffensen ◽  
John A. Bergeron
Keyword(s):  
Pollen Tube ◽  
Growth And Development ◽  
Lilium Longiflorum ◽  
Pollen Tubes ◽  
Mitotic Division ◽  
Generative Nucleus ◽  
Tube Nucleus ◽  
Easter Lily ◽  
Nuclear Component ◽  
Sperm Nuclei

Autoradiography with Ca45 has been used to obtain information about the relation between calcium and chromosomes. Labelled pollen from the Easter lily, Lilium longiflorum, was allowed to develop into pollen tubes between 5 and 6 cm. long in the styles of non-radioactive flowers. All of the nuclei, namely the tube nucleus and the two sperm nuclei, retain Ca45 after this period of growth and development. Since the two sperm nuclei have formed during this interval by the mitotic division of the generative nucleus and growth of the tube has occurred under the influence of the tube nucleus, it is inferred that the calcium was bound in a stable nuclear component, the chromosomes.

scholarly journals Functional identification of lncRNAs in sweet cherry (Prunus avium) pollen tubes via transcriptome analysis using single-molecule long-read sequencing

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Yang Li ◽  
Chuanbao Wu ◽  
Chunsheng Liu ◽  
Jie Yu ◽  
Xuwei Duan ◽  
...  
Keyword(s):  
Pollen Tube ◽  
Single Molecule ◽  
Noncoding Rna ◽  
Sweet Cherry ◽  
Prunus Avium ◽  
Assessment Tool ◽  
Pollen Tubes ◽  
Functional Identification ◽  
Coding Region ◽  
Male Gametes

AbstractSweet cherry (Prunus avium) is a popular fruit with high nutritional value and excellent flavor. Although pollen plays an important role in the double fertilization and subsequent fruit production of this species, little is known about its pollen tube transcriptome. In this study, we identified 16,409 transcripts using single-molecule sequencing. After filtering 292 transposable elements, we conducted further analyses including mRNA classification, gene function prediction, alternative splicing (AS) analysis, and long noncoding RNA (lncRNA) identification to gain insight into the pollen transcriptome. The filtered transcripts could be matched with 3,438 coding region sequences from the sweet cherry genome. GO and KEGG analyses revealed complex biological processes during pollen tube elongation. A total of 2043 AS events were predicted, 7 of which were identified in different organs, such as the leaf, pistil and pollen tube. Using BLASTnt and the Coding-Potential Assessment Tool (CPAT), we distinguished a total of 284 lncRNAs, among which 154 qualified as natural antisense transcripts (NATs). As the NATs could be the reverse complements of coding mRNA sequences, they might bind to coding sequences. Antisense transfection assays showed that the NATs could regulate the expression levels of their complementary sequences and even affect the growth conditions of pollen tubes. In summary, this research characterizes the transcripts of P. avium pollen and lays the foundation for elucidating the physiological and biochemical mechanisms underlying sexual reproduction in the male gametes of this species.

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.

The distribution of calcium in the grass pollen tube

1985 ◽  
Vol 225 (1240) ◽  
pp. 315-327 ◽  
Keyword(s):  
Pollen Tube ◽  
Pollen Dispersal ◽  
Lilium Longiflorum ◽  
Pollen Tubes ◽  
Distal Region ◽  
Tube Growth ◽  
Growth Physiology ◽  
Large Numbers ◽  
The Difference ◽  
Apical Organization

The distribution of calcium in the terminal regions of actively extending pollen tubes of two Gramineae, Zea mays and Pennisetum americanum , has been investigated by chlorotetracycline (CTC) fluorescence and by energy-dispersive X-ray analysis. Neither method reveals a concentration gradient declining from the tip towards the older parts of the tube comparable with that reported from the pollen tubes of Lilium longiflorum . The difference evidently arises from dissimilarities in pollen-tube growth physiology and the apical organization of the tube. Growth is achieved by the insertion of dictyosome-derived vesicles carrying wallprecursor materials at the tube tip. In L . longiflorum these are produced in a subapical zone of the tube, and a characteristic zonation of cytoplasmic organelles in the distal region develops during growth. In the grasses, large numbers of the wall precursor bodies (‘P-particles ’) are produced before pollen dispersal, and are stored in the grain; they are distributed throughout the tube during early growth, and the organelle zonation in the apex is less pronounced. CTC-induced fluorescence is strongly associated with mitochondria, membranes and P-particles, suggesting that the observed distribution of calcium may reflect mainly the distribution of the element held in organelles and membranes rather than mobile Ca 2+ in the cytosol.

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 Hyperoside promotes pollen tube growth by regulating the depolymerization effect of actin-depolymerizing factor 1 on microfilaments in okra

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Biying Dong ◽  
Qing Yang ◽  
Zhihua Song ◽  
Lili Niu ◽  
Hongyan Cao ◽  
...  
Keyword(s):  
Pollen Tube ◽  
Pollen Tube Growth ◽  
Pollen Germination ◽  
Pollen Tubes ◽  
Tube Growth ◽  
Actin Depolymerizing Factor ◽  
Specific Mechanism ◽  
Promoting Effect ◽  
New Research

AbstractMature pollen germinates rapidly on the stigma, extending its pollen tube to deliver sperm cells to the ovule for fertilization. The success of this process is an important factor that limits output. The flavonoid content increased significantly during pollen germination and pollen tube growth, which suggests it may play an important role in these processes. However, the specific mechanism of this involvement has been little researched. Our previous research found that hyperoside can prolong the flowering period of Abelmoschus esculentus (okra), but its specific mechanism is still unclear. Therefore, in this study, we focused on the effect of hyperoside in regulating the actin-depolymerizing factor (ADF), which further affects the germination and growth of pollen. We found that hyperoside can prolong the effective pollination period of okra by 2–3-fold and promote the growth of pollen tubes in the style. Then, we used Nicotiana benthamiana cells as a research system and found that hyperoside accelerates the depolymerization of intercellular microfilaments. Hyperoside can promote pollen germination and pollen tube elongation in vitro. Moreover, AeADF1 was identified out of all AeADF genes as being highly expressed in pollen tubes in response to hyperoside. In addition, hyperoside promoted AeADF1-mediated microfilament dissipation according to microfilament severing experiments in vitro. In the pollen tube, the gene expression of AeADF1 was reduced to 1/5 by oligonucleotide transfection. The decrease in the expression level of AeADF1 partially reduced the promoting effect of hyperoside on pollen germination and pollen tube growth. This research provides new research directions for flavonoids in reproductive development.

scholarly journals Testing of self-(in)compatibility in apricot cultivars from European breeding programmes

2013 ◽  
Vol 40 (No. 2) ◽  
pp. 65-71 ◽  
Author(s):  
D. Milatović ◽  
D. Nikolić ◽  
B. Krška
Keyword(s):  
Fluorescence Microscopy ◽  
Pollen Tube ◽  
Pollen Tube Growth ◽  
Reliable Method ◽  
Pollen Tubes ◽  
Tube Growth ◽  
Self Incompatibility ◽  
Breeding Programmes

Self-(in)compatibility was tested in 40 new apricot cultivars from European breeding programmes. Pollen-tube growth in pistils from laboratory pollinations was analysed using the fluorescence microscopy. Cultivars were considered self-compatible if at least one pollen tube reached the ovary in the majority of pistils. Cultivars were considered self- incompatible if the growth of pollen tubes in the style stopped along with formation of characteristic swellings. Of the examined cultivars, 18 were self-compatible and 22 were self-incompatible. Fluorescence microscopy provides a relatively rapid and reliable method to determine self-incompatibility in apricot cultivars.      

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