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Pollen Tubes (pollen + tubes)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

Prefertilization barriers to interspecific hybridization involving Gossypium hirsutum and four diploid wild species

PLANT BREEDING, Issue 3 2008
S. Ganesh Ram
Abstract Interspecific hybridization among species of cotton has lead to improvement in productivity, earliness, fibre quality and resistance to pests and diseases. However, wide crosses is often limited by the operation of either pre- or/and post-fertilization barriers. An investigation on pollen tube behaviour of four wild species in the pistils of Gossypium hirsutum was taken up. Pollen germination was normal in crosses involving Gossypium triphyllum and Gossypium armourianum and markedly inhibited in the crosses involving Gossypium davidsonii and Gossypium thurberi. Pollen tubes reached the pistils and fertilization was accomplished within 8 h after pollination (HAP) in control cross. Even though delay in pollen tube was a common phenomenon in all the four crosses successful fertilization was observed in crosses involving G. triphyllum and G. armourianum, as they reached the ovary at 24 HAP. In crosses with G. davidsonii and G. thurberi, pollen tubes failed to reach the ovary even at 24 HAP indicating the presence of strong stylar and ovarian incompatibility. Measures to overcome such barriers to interspecific hybridization in the incompatible crosses are discussed. [source]

Mimicry in plant-parasitic fungi

FEMS MICROBIOLOGY LETTERS, Issue 2 2006
Henry K. Ngugi
Abstract Mimicry is the close resemblance of one living organism (the mimic) to another (the model), leading to misidentification by a third organism (the operator). Similar to other organism groups, certain species of plant-parasitic fungi are known to engage in mimetic relationships, thereby increasing their fitness. In some cases, fungal infection can lead to the formation of flower mimics (pseudoflowers) that attract insect pollinators via visual and/or olfactory cues; these insects then either transmit fungal gametes to accomplish outcrossing (e.g. in some heterothallic rust fungi belonging to the genera Puccinia and Uromyces) or vector infectious spores to healthy plants, thereby spreading disease (e.g. in the anther smut fungus Microbotryum violaceum and the mummy berry pathogen Monilinia vaccinii-corymbosi). In what is termed aggressive mimicry, some specialized plant-parasitic fungi are able to mimic host structures or host molecules to gain access to resources. An example is M. vaccinii-corymbosi, whose conidia and germ tubes, respectively, mimic host pollen grains and pollen tubes anatomically and physiologically, allowing the pathogen to gain entry into the host's ovary via stigma and style. We review these and other examples of mimicry by plant-parasitic fungi and some of the mechanisms, signals, and evolutionary implications. [source]

Comparative analysis of the self-incompatibility (S -) locus region of Prunus mume: identification of a pollen-expressed F-box gene with allelic diversity

GENES TO CELLS, Issue 3 2003
Tetsuyuki Entani
Background: Self-incompatibility (SI) in the Solanaceae, Rosaceae and Scrophulariaceae is gametophytically controlled by a single polymorphic locus, termed the S -locus. To date, the only known S -locus product is a polymorphic ribonuclease, termed S -RNase, which is secreted by stylar tissue and thought to act as a cytotoxin that degrades the RNA of incompatible pollen tubes. However, understanding how S -RNase causes S -haplotype specific inhibition of pollen tubes has been hampered by the lack of a cloned pollen S -determinant gene. Results: To identify the pollen S -determinant gene, we investigated the genomic structure of the S -locus region of the S1 - and S7 -haplotypes of Prunus mume (Japanese apricot), and identified 13 genes around the S-RNase gene. Among them, only one F-box gene, termed SLF (S -locus F-box), fulfilled the conditions for a pollen S -determinant gene: (i) together with the S-RNase gene, it is located within the highly divergent genomic region of the S -locus, (ii) it exhibits S -haplotype specific diversity among three analysed S -haplotypes, and (iii) it is specifically expressed in pollen, but not in the styles or leaves. Conclusion: The results indicate that SLF is a prime candidate for the pollen S -determinant gene of SI. [source]

Claviceps purpurea: molecular aspects of a unique pathogenic lifestyle

MOLECULAR PLANT PATHOLOGY, Issue 5 2004
PAUL TUDZYNSKI
SUMMARY Claviceps purpurea is a ubiquitous pathogen of cereals and grasses, causing Ergot disease, which results in substitution of grains by sclerotia. These overwintering structures contain ergot-alkaloids, which can cause severe intoxication in mammals. C. purpurea is an interesting model system for the study of host,pathogen interaction. It displays strict organ specificity, attacking exclusively young grass ovaries. It is optimally adapted to this special niche of infection, probably by mimicry of pollen tubes: there are no resistance genes known, and no effective resistance reactions can be detected in the early steps of infection. In this early phase of host tissue colonization the fungus shows directed, almost unbranched growth towards the base of the ovary. Thus, C. purpurea represents one of the few systems in which directed growth in filamentous fungi can be studied. Finally, the fungus behaves as a true biotroph in planta, although it can be easily grown in axenic culture. We describe here the tools available to study this interesting pathogen, report on recent molecular investigations concerning the role of cell-wall-degrading enzymes and of reactive oxygen species in this specialized interaction, and present an update of the signalling cascades involved in early events of pathogenesis. [source]

Identification of hyperpolarization-activated calcium channels in apical pollen tubes of Pyrus pyrifolia

NEW PHYTOLOGIST, Issue 3 2007
Hai-Yong Qu
Summary ,,The pollen tube has been widely used to study the mechanisms underlying polarized tip growth in plants. A steep tip-to-base gradient of free cytosolic calcium ([Ca2+]cyt) is essential for pollen-tube growth. Local Ca2+ influx mediated by Ca2+ -permeable channels plays a key role in maintaining this [Ca2+]cyt gradient. ,,Here, we developed a protocol for successful isolation of spheroplasts from pollen tubes of Pyrus pyrifolia and identified a hyperpolarization-activated cation channel using the patch-clamp technique. ,,We showed that the cation channel conductance displayed a strong selectivity for divalent cations, with a relative permeability sequence of barium (Ba2+) , Ca2+ > magnesium (Mg2+) > strontium (Sr2+) > manganese (Mn2+). This channel conductance was selective for Ca2+ over chlorine (Cl,) (relative permeability PCa/PCl = 14 in 10 mm extracellular Ca2+). We also showed that the channel was inhibited by the Ca2+ channel blockers lanthanum (La3+) and gadolinium (Gd3+). Furthermore, channel activity depended on extracellular pH and pollen viability. ,,We propose that the Ca2+ -permeable channel is likely to play a role in mediating Ca2+ influx into the growing pollen tubes to maintain the [Ca2+]cyt gradient. [source]

Free IAA in stigmas and styles during pollen germination and pollen tube growth of Nicotiana tabacum

PHYSIOLOGIA PLANTARUM, Issue 1 2008
Dan Chen
Although many studies have emphasized the importance of auxin in plant growth and development, the thorough understanding of its effect on pollen,pistil interactions is largely unknown. In this study, we investigated the role of free IAA in pollen,pistil interactions during pollen germination and tube growth in Nicotiana tabacum L. through using histo and subcellular immunolocalization with auxin monoclonal antibodies, quantification by HPLC and ELISA together with GUS staining in DR5::GUS -transformed plants. The results showed that free IAA in unpollinated styles was higher in the apical part and basal part than in the middle part, and it was more abundant in the transmitting tissue (TT). At the stage of pollen germination, IAA reached its highest content in the stigma and was mainly distributed in TT. After the pollen tubes entered the styles, the signal increased in the part where pollen tubes would enter and then rapidly declined in the part where pollen tubes had penetrated. Subcellular localization confirmed the presence of IAA in TT cells of stigmas and styles. Accordingly, a schematic diagram summarizes the changing pattern of free IAA level during flowering, pollination and pollen tube growth. Furthermore, we presented evidence that low concentration of exogenous IAA could, to a certain extent, facilitate in vitro pollen tube growth. These results suggest that IAA may be directly or indirectly involved in the pollen,pistil interactions. Additionally, some improvements of the IAA immunolocalization technique were made. [source]

Cryptic self-incompatibility and distyly in Hedyotis acutangula Champ. (Rubiaceae)

PLANT BIOLOGY, Issue 3 2010
X. Wu
Abstract Distyly, floral polymorphism frequently associated with reciprocal herkogamy, self- and intramorph incompatibility and secondary dimorphism, constitutes an important sexual system in the Rubiaceae. Here we report an unusual kind of distyly associated with self- and/or intramorph compatibility in a perennial herb, Hedyotis acutangula. Floral morphology, ancillary dimorphisms and compatibility of the two morphs were studied. H. acutangula did not exhibit precise reciprocal herkogamy, but this did not affect the equality of floral morphs in the population, as usually found in distylous plants. Both pin and thrum pollen retained relatively high viability for 8 h. The pollen to ovule ratio was 72.5 in pin flowers and 54.4 in thrum flowers. Pistils of pin flowers remained receptive for longer than those of thrum flowers. No apparent difference in the germination rate of pin and thrum pollen grains was observed when cultured in vitro, although growth of thrum pollen tubes was much faster than that of pin pollen tubes. Artificial pollination revealed that pollen tube growth in legitimate intermorph crosses was faster than in either intramorph crosses or self-pollination, suggesting the occurrence of cryptic self-incompatibility in this species. Cryptic self-incompatibility functioned differently in the two morphs, with pollen tube growth rates after legitimate and illegitimate pollination much more highly differentiated in pin flowers than in thrum flowers. No fruit was produced in emasculated netted flowers, suggesting the absence of apomixis. Our results indicate that H. acutangula is distylous, with a cryptic self-incompatibility breeding system. [source]

Immunolocalization of the PmSUC1 Sucrose Transporter in Plantago major Flowers and Reporter-Gene Analyses of the PmSUC1 Promoter Suggest a Role in Sucrose Release from the Inner Integument

PLANT BIOLOGY, Issue 3 2007
C. Lauterbach
Abstract: This paper presents a detailed analysis of the PmSUC1 gene from Plantago major, of its promoter activity in Arabidopsis, and of the tissue specific localization of the encoded protein in Plantago. PmSUC1 promoter activity was detected in the innermost layer of the inner integument (the endothel) of Arabidopsis plants expressing the gene of the green fluorescent protein (GFP) under the control of the PmSUC1 promoter. This promoter activity was confirmed with a PmSUC1-specific antiserum that identified the PmSUC1 protein in the endothel of Plantago and of Arabidopsis plants expressing the PmSUC1 gene under the control of its own promoter. PmSUC1 promoter activity and PmSUC1 protein were also detected in pollen grains during maturation inside the anthers and in pollen tubes during and after germination. These results demonstrate that PmSUC1 is involved in sucrose partitioning to the young embryo and to the developing pollen and growing pollen tube. In the innermost cell layer of the inner integument, a tissue that delivers nutrients to the endosperm and the embryo, PmSUC1 may catalyze the release of sucrose into the apoplast. [source]

Prefertilization barriers to interspecific hybridization involving Gossypium hirsutum and four diploid wild species

Stylar glycoproteins bind to S-RNase in vitro

THE PLANT JOURNAL, Issue 3 2005
Felipe Cruz-Garcia
Summary S-RNases determine the specificity of S -specific pollen rejection in self-incompatible plants of the Solanaceae, Rosaceae, and Scrophulariaceae. They are also implicated in at least two distinct types of unilateral interspecific incompatibility in Nicotiana. However, S-RNase itself is not sufficient for most types of pollen rejection, and evidence for its direct interaction with pollen tubes is limited. Thus, non-S-RNase factors also are required for pollen rejection. As one approach to identifying such factors, we tested whether SC10 -RNase from Nicotiana alata would bind to other stylar proteins in vitro. SC10 -RNase was immobilized on Affi-gel, and binding proteins were analyzed by SDS-PAGE and immunoblotting. In addition to SC10 -RNase and a small protein similar to lily chemocyanin, the most prominent binding proteins include NaTTS, 120K, and NaPELPIII, these latter three being arabinogalactan proteins previously shown to interact directly with pollen tubes. We also show that SC10 -RNase and these glycoproteins migrate as a complex in a native PAGE system. Our hypothesis is that S-RNase forms a complex with these glycoproteins in the stylar ECM, that the glycoproteins interact directly with the pollen tubes and thus that the initial interaction between the pollen tube and S-RNase is indirect. [source]

Essential role of the V-ATPase in male gametophyte development

THE PLANT JOURNAL, Issue 1 2005
Jan Dettmer
Summary Intracellular pH homeostasis is a prerequisite for biological processes and requires the action of proton pumps. The vacuolar H+ -ATPase (V-ATPase) is involved in regulating pH in endomembrane compartments of all eukaryotic cells. In plants, there is an additional endomembrane proton pump, H+ -pyrophosphatase (H+ -PPase). However, the relative roles of the two types of pumps in endomembrane acidification and energization of secondary active transport are unclear. Here, we show that a strong T-DNA insertion allele of VHA-A, the single copy gene encoding the catalytic subunit of the Arabidopsis V-ATPase, causes complete male and partial female gametophytic lethality. Severe changes in the morphology of Golgi stacks and Golgi-derived vesicles in male gametophytes are the first visible symptoms of cell degeneration leading to a failure to develop mature pollen. Similar effects on Golgi morphology were observed in pollen tubes when growth was blocked by Concanamycin A, a specific V-ATPase inhibitor. Taken together, our results suggests that V-ATPase function is essential for Golgi organization and development of the male gametophyte. [source]

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

THE PLANT JOURNAL, Issue 6 2004
Cláudia Rato
Summary 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-(,-amino-Lys75)-[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 ([Ca2+]c). In long pollen tubes, apical CaM activity was also found to oscillate with a period similar to [Ca2+]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 [Ca2+]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. [source]

Pistil traits and flower fate in apricot (Prunus armeniaca)

ANNALS OF APPLIED BIOLOGY, Issue 3 2009
J. Rodrigo
Abstract Although pollination is essential for both seed and fruit set in most angiosperms, even after an adequate pollination, only a fraction of the flowers develop into fruits. The role played by floral traits on reproductive success is well known, but the possible influence of pistil traits has been overlooked, probably because of the difficulty of non-destructive pistil examination. The aim of this work was to examine the influence of several pistil traits on reproductive success in apricot (Prunus armeniaca). For this purpose, in a population of individually labelled flowers, the styles were cut off once the pollen tubes had reached the ovary but prior to the achievement of fertilisation. This approach allowed relating several morphological and physiological pistil parameters in the dissected styles and stigmas to the subsequent set or abscission of the corresponding ovary that remained in the plant. Under the same pollination conditions, the flowers that finally set a fruit show a larger stigmatic area and a higher number of pollen grains, pollen tubes growing along the style and xylem vessels surrounding the transmitting tissue than flowers that abscise before the establishment of fruit set. Furthermore, starch is present in the transmitting tissue of the style in all the flowers that develop into fruits but only in half of the flowers that abscise. The examined pistil traits established prior to fertilisation are related to flower fate, suggesting that the capacity of a flower to become a fruit could be preconditioned at anthesis. [source]

Causes of spatial patterns of fruit set in waratah: Temporal vs. spatial interactions between flowers on an inflorescence

AUSTRAL ECOLOGY, Issue 1 2009
ROBERT J. WHELAN
Abstract Spatial patterns of fruit set within inflorescences may be controlled by pollination, nutrient allocation, or inflorescence architecture. Generally, flowers that have spatial and/or temporal precedence are more likely to set fruits. We sought to separate these factors by comparing patterns of fruit set on inflorescences of two species of Telopea (Proteaceae); one that flowers from the tip to the base of the rachis, the other from base to tip. In both species, most fruits were set at the top of the inflorescence (the last flowers to open for T. speciosissima) and this was extreme for T. mongaensis, where the top flowers open first. Fruit set was not generally limited by inadequate pollination for either T. mongaensis or T. speciosissima, as hand pollinations did not increase fruit set and many abscised flowers contained pollen tubes. In T. speciosissima, we tested whether removal of developing topmost fruits would ,release' those that had initiated but not yet aborted lower down. There was no significant effect. Plant hormones can increase the degree to which a developing fruit is a sink for nutrients, so we applied cytokinin to the developing lower fruits on some inflorescences. There was no significant effect of the hormone treatment. We conclude that temporal precedence may contribute to the skewed pattern of fruit set in T. mongaensis, because there was an extreme concentration of fruit set on the distal part of the inflorescences, but it cannot explain this pattern of fruit set in T. speciosissima, where the distal flowers are the last to open. Some other process must therefore constrain fruit set to the topmost flowers in an inflorescence. While cytokinin application had no significant effect, the power of this experiment was low and we consider that the hypothesis of hormonal control is worth further exploration. [source]

Mode of pollen tube growth in pistils of Ticodendron incognitum (Ticodendraceae, Fagales) and the evolution of chalazogamy

BOTANICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2008
AKIKO SOGO
Ticodendron incognitum is the sole species of the Ticodendraceae, which was established as a new family in the Fagales less than 20 years ago. Considering the diverse modes of pollen tube growth observed in other Fagales, we investigated the growth of pollen tubes in the pistil of Ticodendron. At the time of pollination, T. incognitum had four immature ovules in a bilocular ovary, thus exhibiting delayed fertilization, as in other Fagales. During the period when fertilization was delayed, pollen tube growth in the pistil was intermittent, consisting of five steps associated with development of the ovules and embryo sacs. Four cessation sites occurred: in the style, in the tissue of the upper part of the ovary, inside and outside of the funicle and at the chalaza. A single pollen tube eventually reaches a mature embryo sac through the chalaza in one of the four ovules. While both delayed fertilization and intermittent pollen tube growth play a role in male and female gametophyte selection, as in other Fagales, the five-step process of pollen tube growth through the chalaza (i.e. chalazogamy) is characteristic of lineages of the Casuarinaceae, Ticodendraceae and Betulaceae (the latter with the loss of one step). © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 157, 621,631. [source]

Reproductive biology of Boswellia serrata, the source of salai guggul, an important gum-resin

BOTANICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2005
V. G. SUNNICHAN
Detailed studies were carried out on the phenology, floral biology, pollination ecology and breeding system of Boswellia serrata Roxb. (Burseraceae) the source of ,salai guggul'. The trees remain leafless during the entire period of flowering and fruiting. The inflorescence is a terminal raceme and produces up to 90 bisexual, actinomorphic flowers. On average a flower produces 10 044 ± 1259 starch-filled pollen grains. About 85% of the fresh pollen grains are viable; the pollen to ovule ratio is 3348 : 1. The stigma is of the wet papillate type. The style is hollow with three flattened stylar canals filled with a secretion product. The stylar canals are bordered by a layer of glandular canal cells. The inner tangential wall of the canal cells shows cellulose thickenings. The ovary is trilocular and bears three ovules, one in each locule. Flowers offer nectar and pollen as rewards to floral visitors. The giant Asian honey bee (Apis dorsata) and A. cerana var. indica(Indian honey bee) are the effective pollinators. The species is self-incompatible and the selfed pollen tubes are inhibited soon after their entry into the stigma. Self-pollen tubes develop a characteristic ,isthmus' as a result of enlargement of the tube soon after emergence through the narrow germ pore. Cross-pollinated flowers allowed normal pollen germination and pollen tube growth, and resulted in fruit- and seed-set. Under open pollination fruit-set was only about 10%. Although manual cross-pollinations increased fruit set, it was only up to about 20%. Low fruit set appears to be the result of inadequate cross-pollination and other constraints, presumably limitation of available nutrients. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society, 2005, 147, 73,82. [source]