Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Pollen Tube”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources
PubMed2002

Programmed cell death of Pinus nucellus in response to pollen tube penetration.

In ovules of Pinus densiflora, pollen tubes elongate and branch into the nucellar tissue in the direction of the female gametophyte. After pollination, nucellar cells located around the pollen grain and tube die off. We showed here that the nuclei of the nucellar cells were stained by TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP-fluorescein nick end labeling). The number of TUNEL-positive cells increased during pollen tube growth. The tips of pollen tube branches protruded into the nucellar cells to form a convex-concave junction. At this junction, the cell membrane of nucellar cells was separated from the cell wall and the protoplast shrank. Small vesicles and amorphous materials were released from the protoplast into the space between the cell membrane and wall. Vacuoles were collapsed, chromatin was condensed, and mitochondria and plastids were deteriorated in the shrunken protoplast. Agarose gel analysis of DNA isolated from the ovules showed a DNA ladder, suggesting that the nuclear DNA had undergone internucleosomal cleavage. These results suggest that nucellar cells undergo programmed cell death in response to pollen tube penetration with some features resembling apoptosis and other features peculiar to nucellar cells.

Journal Article↗
PubMed2005

Morphological anomalies in pollen tubes of Actinidia deliciosa (kiwi) exposed to 50 Hz magnetic field.

The role of the pollen grain, with respect to the reproductive process of higher plants, is to deliver the spermatic cells to the embryo sac for egg fertilisation. Delivery occurs through the pollen tube, a self produced organ that is generated when the pollen grain reaches the stigma surface. The effect of magnetic fields on pollen tube growth was reported in a recent publication by Germanà et al. Pollen tube growth is an interesting candidate for the detailed study of the effects of electromagnetic fields on cytoplasmic structures and organelles. In this research Actinidia deliciosa (kiwifruit) pollen grains were germinated in the presence of an alternating magnetic field (50 Hz). Our results, although of preliminary nature, show that pollen tube growth is affected by magnetic fields. The analysis of the observed anomalies in the pollen tube appear to be the result of changes in the ionic charges within the pollen tube cytoplasm.

Actinidia↗
PubMed1979

Studies on the physiology of pollen and pollen tube growth. IV Eschscholtzia californica Cham.

Eschscholtzia californica stigmas with germinating pollen at different stages of development were the subject of histochemical studies which aimed the localization of several enzymes like phosphorylase, leucine amino peptidase, nonspecific esterase, cytochrome oxidase, aldolase, alpha-glycerophosphate dehydrogenase, succinate dehydrogenase, malate dehydrogenase, monoamine oxidase, alpha-galactosidase, beta-glucosidase and beta-galactosidase. Pollen and pollen tubes were shown to contain starch, lipid, proteins and soluble sugars as the storage products. These storage products were utilized during germination and tube growth. The role of different enzymes in the process of germination and tube growth is discussed. From the distribution of oxidoreductases it is inferred that respiration plays an essential role in the tube growth. During pollen germination probably the reserve proteins were transported to pollen tube tip. The increase of activity of alpha-and beta-galactosidase in pollen tubes indicates on their involvement in carbohydrate metabolism. The role of alpha-galactosidase in the metabolism of galactolipids is also inferred. Similarly, the reaction catalysed by beta-glucosidase resulted in the production of aglycon and glucose; of these the former possibly act as a substrate of peroxidase. Some of the glycosidases diffused out of pollen wall on the stigma and participated in the release of free sugars of the female tissue.

Electron Transport Complex IV↗
PubMed2005

Characterization of pollen tube development in Pinus strobus (Eastern white pine) through proteomic analysis of differentially expressed proteins.

The differentially expressed proteins in pollen tubes indicate their specific roles in this stage of male gametophyte development. To isolate these proteins, 2-DE was done using ungerminated pollen and 2-day-old pollen tubes of Pinus strobus. Results show that 645 and 647 protein spots were clearly resolved from pollen grains and pollen tubes, respectively. Thirty-eight protein spots were expressed only in pollen tubes, while 19 increased in intensity. MALDI-TOF MS was used to generate tryptic peptide masses that were submitted to Mascot for identification. Of the differentially expressed proteins, 12% matched with hypothetical proteins, 33% did not hit any protein, and for the 55%, a putative function was assigned based on similarity of sequences with previously characterized proteins. Therefore, pollen tube development can be characterized by the cellular activities that involve metabolism, stress/defense response, gene regulation, signal transduction, and cell wall formation. This study expands our understanding of the changes in protein expression associated with pollen tube development and provides insights into the molecular programs that separate the development of the pollen tubes from pollen grains. This is the first report that describes a global analysis of differentially expressed proteins from the pollen tube of any seed plant.

Cell Wall↗
PubMed2000

Attractive and repulsive interactions between female and male gametophytes in Arabidopsis pollen tube guidance.

Sexual reproduction in plants, unlike that of animals, requires the action of multicellular haploid gametophytes. The male gametophyte (pollen tube) is guided to a female gametophyte through diploid sporophytic cells in the pistil. While interactions between the pollen tube and diploid cells have been described, little is known about the intercellular recognition systems between the pollen tube and the female gametophyte. In particular, the mechanisms that enable only one pollen tube to interact with each female gametophyte, thereby preventing polysperm, are not understood. We isolated female gametophyte mutants named magatama (maa) from Arabidopsis thaliana by screening for siliques containing half the normal number of mature seeds. In maa1 and maa3 mutants, in which the development of the female gametophyte was delayed, pollen tube guidance was affected. Pollen tubes were directed to mutant female gametophytes, but they lost their way just before entering the micropyle and elongated in random directions. Moreover, the mutant female gametophytes attracted two pollen tubes at a high frequency. To explain the interaction between gametophytes, we propose a monogamy model in which a female gametophyte emits two attractants and prevents polyspermy. This prevention process by the female gametophyte could increase a plant's inclusive fitness by facilitating the fertilization of sibling female gametophytes. In addition, repulsion between pollen tubes might help prevent polyspermy. The reproductive isolations observed in interspecific crosses in Brassicaceae are also consistent with the monogamy model.

Arabidopsis↗
PubMed2004

Pectin and the role of the physical properties of the cell wall in pollen tube growth of Solanum chacoense.

The cell wall is one of the structural key players regulating pollen tube growth, since plant cell expansion depends on an interplay between intracellular driving forces and the controlled yielding of the cell wall. Pectin is the main cell wall component at the growing pollen tube apex. We therefore assessed its role in pollen tube growth and cytomechanics using the enzymes pectinase and pectin methyl esterase (PME). Pectinase activity was able to stimulate pollen germination and tube growth at moderate concentrations whereas higher concentrations caused apical swelling or bursting in Solanum chacoense Bitt. pollen tubes. This is consistent with a modification of the physical properties of the cell wall affecting its extensibility and thus the growth rate, as well as its capacity to withstand turgor. To prove that the enzyme-induced effects were due to the altered cell wall mechanics, we subjected pollen tubes to micro-indentation experiments. We observed that cellular stiffness was reduced and visco-elasticity increased in the presence of pectinase. These are the first mechanical data that confirm the influence of the amount of pectins in the pollen tube cell wall on the physical parameters characterizing overall cellular architecture. Cytomechanical data were also obtained to analyze the role of the degree of pectin methyl-esterification, which is known to exhibit a gradient along the pollen tube axis. This feature has frequently been suggested to result in a gradient of the physical properties characterizing the cell wall and our data provide, for the first time, mechanical support for this concept. The gradient in cell wall composition from apical esterified to distal de-esterified pectins seems to be correlated with an increase in the degree of cell wall rigidity and a decrease of visco-elasticity. Our mechanical approach provides new insights concerning the mechanics of pollen tube growth and the architecture of living plant cells.

Cell Wall↗
PubMed1982

Cytochemical localization of some hydrolases in the pollen and pollen tubes of Amaryllis vittata Ait.

Some hydrolases are localized cytochemically in the pollen and pollen tubes of Amaryllis vittata Ait. The function of different enzymes is discussed in relation to pollen tubes morphogenesis. Activity of most of the enzymes was confined to colpus region, pollen wall and general cytoplasm of pollen and pollen tube. The activity of hydrolytic enzymes like acid monophosphoesterase and lipase and was nil in the exine of both germinated and ungerminated pollen, whereas intense reaction for esterase was observed in exine. Enzyme activity increased after germination which suggest the hydrolysis of stored metabolites and synthesis of proteins and other metabolites for the active growth of pollen tube. Intense reaction for enzymes like alkaline phosphomonoesterase, ATP-ase, 5-nucleotidase etc. at the tip region of pollen tube suggest their role in physiological processes associated with exchange of materials through intercellular transport during tube wall polysaccharide biogenesis.

5'-Nucleotidase↗
PubMed2004

Calmodulin activity and cAMP signalling modulate growth and apical secretion in pollen tubes.

Our present understanding implicates both calmodulin (CaM) and 3',5'-cyclicAMP (cAMP) in the regulation of pollen tube growth. However, downstream molecules of these signalling pathways and the cellular processes they modulate remain largely unknown. In order to elucidate the role of CaM, we mapped its activity in growing pollen tubes. 2-chloro-(epsilon-amino-Lys(75))-[6-4-(N,N'-diethylaminophenyl)-1,3,5-triazin-4-yl]-calmodulin (TA-CaM) and fluorescein-calmodulin (FL-CaM), fluorescent analogues of CaM, were loaded into pollen tubes and CaM activity was mapped by fluorescence ratio imaging. It was found that CaM activity exhibits a tip-focused gradient, similar to the distribution of cytosolic-free calcium ([Ca(2+)](c)). In long pollen tubes, apical CaM activity was also found to oscillate with a period similar to [Ca(2+)](c) (40-80 sec). This oscillatory behaviour was not observed in small pollen tubes or in tubes that had stopped growing. Changes in CaM activity within the dome of the pollen tube apex resulting from the photolysis of caged photolysis of RS-20 (a peptide antagonist of CaM) induced re-orientation of the growth axis, suggesting that CaM is also involved in the guidance mechanism. CaM activity was strongly modulated by intracellular changes in cAMP (induced by activators and antagonists of adenylyl cyclase). These results indicate that the action of this protein is dependent not solely on [Ca(2+)](c) but also on a cross-talk with other signalling pathways. A putative target of this cross-talk is the secretory machinery as observed in pollen tubes loaded with the FM (N-(3-triethylammoniumpropyl)-4-(4-dibutylamino)styryl)pyridinium dibromide 1-43 dye and exposed to different antagonists and activators of these molecules. Our data thus suggest that pollen tube growth and orientation depend on an intricate cross-talk between multiple signalling pathways in which CaM is a key element.

Calcium↗
PubMed2006

Calcium-dependent protein kinase isoforms in Petunia have distinct functions in pollen tube growth, including regulating polarity.

Calcium is a key regulator of pollen tube growth, but little is known concerning the downstream components of the signaling pathways involved. We identified two pollen-expressed calmodulin-like domain protein kinases from Petunia inflata, CALMODULIN-LIKE DOMAIN PROTEIN KINASE1 (Pi CDPK1) and Pi CDPK2. Transient overexpression or expression of catalytically modified Pi CDPK1 disrupted pollen tube growth polarity, whereas expression of Pi CDPK2 constructs inhibited tube growth but not polarity. Pi CDPK1 exhibited plasma membrane localization most likely mediated by acylation, and we present evidence that suggests this localization is critical to the biological function of this kinase. Pi CDPK2 substantially localized to as yet unidentified internal membrane compartments, and this localization was again, at least partially, mediated by acylation. In contrast with Pi CDPK1, altering the localization of Pi CDPK2 did not noticeably alter the effect of overexpressing this isoform on pollen tube growth. Ca(2+) requirements for Pi CDPK1 activation correlated closely with Ca(2+) concentrations measured in the growth zone at the pollen tube apex. Interestingly, loss of polarity associated with overexpression of Pi CDPK1 was associated with elevated cytosolic Ca(2+) throughout the bulging tube tip, suggesting that Pi CDPK1 may participate in maintaining Ca(2+) homeostasis. These results are discussed in relation to previous models for Ca(2+) regulation of pollen tube growth.

Base Sequence↗
PubMed1995

Calcium Channel Activity during Pollen Tube Growth and Reorientation.

We have shown previously that the inhibition of pollen tube growth and its subsequent reorientation in Agapanthus umbellatus are preceded by an increase in cytosolic free calcium ([Ca2+]c), suggesting a role for Ca2+ in signaling these processes. In this study, a novel procedure was used to measure Ca2+ channel activity in living pollen tubes subjected to various growth reorienting treatments (electrical fields and ionophoretic microinjection). The method involves adding extracellular Mn2+ to quench the fluorescence of intracellular Indo-1 at its ca2+-insensitive wavelength (isosbestic point). The spatial and temporal kinetics of Ca2+ channel activity correlated well with measurements of [Ca2+]c dynamics obtained by fluorescence ratio imaging of Indo-1. Tip-focused gradients in Ca2+ channel activity and [Ca2+]c were observed and quantified in growing pollen tubes and in swollen pollen tubes before reoriented growth. In nongrowing pollen tubes, Ca2+ channel activity was very low and [Ca2+]c gradients were absent. Measurements of membrane potential indicated that the growth reorienting treatments induced a depolarization of the plasma membrane, suggesting that voltage-gated Ca2+ channels might be activated.

Journal Article↗
PubMed1991

Action of the Style Product of the Self-Incompatibility Gene of Nicotiana alata (S-RNase) on in Vitro-Grown Pollen Tubes.

The products of the S-locus expressed in female tissues of Nicotiana alata are ribonucleases (S-RNases). The arrest of growth of incompatible pollen tubes in styles may result from entry of the S-RNase into the pollen tube and degradation of pollen tube RNA. We investigated the action of isolated S-RNases on pollen tubes grown in vitro and found that S-RNase is taken up by the pollen without substantial alteration. The S-RNases inhibit incorporation of exogenously added radioactive amino acids into protein by the germinated pollen. The S-RNases also inhibit in vitro translation of pollen tube RNA in a wheat germ cell-free extract. We found no evidence for a specific mRNA substrate for the S-RNases, which implies that if RNase activity is involved in the control of self-incompatibility, allelic specificity is more likely to depend on the selective uptake of S-RNases into pollen tubes or their selective activation or inactivation by pollen factors, rather than cleavage of a specific substrate. Heat treating S2-RNase largely destroys its RNase activity but increases its inhibitory effect on in vitro pollen tube growth. This effect is not due to an increased uptake of S2-RNase by the pollen but is associated with a greatly enhanced accumulation of S2-RNase on the outer surface of the pollen grains.

Journal Article↗
PubMed2003

ROP GTPase regulation of pollen tube growth through the dynamics of tip-localized F-actin.

Pollen tubes expand by tip growth and extend directionally toward the ovule to deliver sperms during pollination. They provide an excellent model system for the study of cell polarity control and tip growth, because they grow into uniformly shaped cylindrical cells in culture. Mechanisms underlying tip growth are poorly understood in pollen tubes. It has been demonstrated that ROP1, a pollen-specific member of the plant-specific Rop subfamily of Rho GTPases, is a central regulator of pollen tube tip growth. Recent studies in pollen from Arabidopsis and other species have revealed a ROP-mediated signalling network that is localized to the apical PM region of pollen tubes. The results provide evidence that the localization of this signalling network establishes the site for tip growth and the localized activation of this signalling network regulates the dynamics of tip F-actin. These results have shown that the ROP1-mediated dynamics of tip F-actin is a key cellular mechanism behind tip growth in pollen tubes. Current understanding of the molecular basis for the regulation of the tip actin dynamics will be discussed.

Actins↗
PubMed2005

Comparison of F-actin fluorescent labeling methods in pollen tubes of Lilium davidii.

Fluorescence labeling of F-actin in pollen tubes by various methods has produced inconsistent results in the literature. Here, we report that EGTA, which was always used in fixative buffers in the past and thought to help cytoskeleton stabilization, can significantly affect F-actin distribution and lead to the formation of thick F-actin bundles at the tip of the pollen tube. We also found that vacuum-infiltration for the first 5 min during pollen tube fixation can better preserve normal cytoplasm structure and F-actin distribution. In contrast, m-maleimidobenzoic acid N-hydroxysuccinimide ester (MBS) treatment before chemical fixation resulted in a shortening of the free zone of thick F-actin bundles in the pollen tube tip. Taken together, our results suggest that exclusion of EGTA and MBS from the fixative buffer, in combination with vacuum-infiltration in the first 5 min of fixation, can improve F-actin fluorescence labeling in pollen tubes of Lilium davidii.

Actins↗
PubMed1997

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

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.

Calcium Chloride↗
PubMed1972

The Nutritional Role of Pistil Exudate in Pollen Tube Wall Formation in Lilium longiflorum: I. Utilization of Injected Stigmatic Exudate.

A quantity of labeled stigmatic exudate, collected from detached Lilium longiflorum (cv. Ace) pistils labeled with d-glucose-1-(14)C, was fractionated on Sephadex G-100 and the polysaccharide component, G-100-I, was injected into the hollow styles of unlabeled detached pistils (cv. Ace) which had been removed on the day after anthesis from the plant. Injected pistils were immediately cross-pollinated with L. longiflorum (cv. No. 44) pollen. Eighty-four hours later, pistils were dissected to recover the pollen tubes, expended exudate, and labeled tissues of the stigma and style. Distribution of label revealed that at least 25% of the carbohydrate substance in excised pollen tubes was derived from G-100-I. The composition of expended exudate adhering to pollen tubes, of pollen tube cytoplasm, and of pollen tube walls suggests that utilization of exudate by growing pollen tubes involves uptake and incorporation into pollen tube cytoplasm of exudate polysaccharide fragments followed by extensive metabolism of at least a portion of the incorporated carbohydrate prior to its utilization for pollen tube wall biosynthesis. Results suggest the presence of at least two polysaccharide components in G-100-I, one which resists major degradation following injection into the style and another which undergoes measurable degradation both before and after entry into the pollen tube.

Journal Article↗
PubMed2001

Detection and localization of pectin methylesterase isoforms in pollen tubes of Nicotiana tabacum L.

Pectin methylesterases (PMEs) were detected in tobacco ( Nicotiana tabacum) pollen tubes grown in vitro. Seven PME isoforms exhibiting a wide isoelectric-point (pI) range (5.3-9.1) were found in crude extracts of pollen tubes. These isoforms were mainly retrieved in supernatants after low- and high-speed separation of the crude extract. Two isoforms, with pIs 5.5 and 7.3 and molecular weight about 158 kDa, were detected by immunoblotting with anti-flax PME antiserum. Localization of pectins and PME isoforms in pollen tubes was investigated by immunogold labelling with JIM5 monoclonal antibodies and anti-flax PME antiserum, respectively. In germinated pollen grains, two PME isoforms were mainly detected in the exine, Golgi apparatus and secretory vesicles. In pollen tubes the same two PME isoforms were distributed along the outer face of the plasma membrane in the vicinity of the inner layer of the cell wall, in the Golgi and around secretory vesicles. In pollen grains, PME isoforms were, in some cases, mixed with acidic pectins in proximity to the outer surface of the plasma membrane. In pollen tubes the presence of PMEs inside secretory vesicles carrying esterified pectins supports the hypothesis that, during pollen tube growth, PMEs could be transferred by secretory vesicles in a precursor form and be activated at the tip where exocytosis takes place.

Blotting, Western↗
PubMed2005

Intermittent pollen-tube growth in pistils of alders (Alnus).

In alders, where fertilization occurs approximately 8 weeks after pollination, the pollen tube (male gametophyte) grows intermittently in four steps in close association with the development of the ovary and its ovules. Pollen tubes stop growing in the style, at the ovarian locule, and at the chalaza (ovule), before reaching an embryo sac for fertilization. At the stage when the ovary develops an ovule primordium in each of the two locules, many pollen tubes germinate on the stigma, and a few of them reach the style, where they remain for approximately 7 weeks. Thereafter, a single tube resumes growing; with a short stop in the upper space of the ovarian locule, it reaches the older of the two ovules when it has developed a two-nucleate embryo sac. Except in the last step, where the tube grows from the chalaza to an embryo sac (female gametophyte), an eight-nucleate mature embryo sac is not necessary for pollen-tube guidance in the pistil. Although the intermittent pollen-tube growth appears to play an important role in the selection of a single pollen tube from many and one ovule from two, its detection provides insight into the study of the mechanism of pollen-tube guidance.

Alnus↗
PubMed2002

[The ultracytochemical localization of ATPase activity in pollen tube and stigma of Fagopyrum esculentum after compatible and incompatible pollination].

Ultracytochemical localization of adenosine triphosphatase (ATPase) activity in stigmas, pollens and pollen tubes of Fagopyrum esculentum was performed with the cytochemical method of lead phosphate precipitation. The results were as follows: (1) Lower activities of ATPase appeared in stigma cells at 0.5 hour after compatible and incompatible pollination. Stigma surface and pollen grains attached on stigma showed higher ATPase activities after compatible pollination and lower or no activities after incompatible pollination at 0.5 hour. ATPase localized on endoplasmic reticula and sperm cell in pollen grain. (2) Lower ATPase activities appeared both in stigma cells and pollen tubes in style at 1.5 hours after incompatible pollination. Pollen tube stopped growing and the degeneration of its cytoplasma began; on the contrary, at 1.5 hours after compatible pollination, higher ATPase activities were detected both in stigma cells and pollen tube in style. ATPase localized mainly on plasmolemma, in cytoplasmic matrix of stigma cells and in mitochondria, dictyosome, plastid envelop, and on the wall of pollen tube as well. The present study indicated that the stop of pollen tube growth after self-incompatibility of Fagopyrum esculentum resulted not only from the nutrient starvation of pollen tube, but also from its metabolic disorder in incompatible style.

Adenosine Triphosphatases↗