The ultrastructure and ontogeny of pollen in Helleborus foetidus L. I. The development of the tapetum and Ubisch bodies.
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Meiosis↗
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Tetrad analysis possible in Arabidopsis with mutation of the QUARTET (QRT) genes.
Two Arabidopsis thaliana genes, QRT1 and QRT2, are required for pollen separation during normal development. In qrt mutants, the outer walls of the four meiotic products of the pollen mother cell are fused, and pollen grains are released in tetrads. Pollen is viable and fertile, and the cytoplasmic pollen contents are discrete. Pollination with a single tetrad usually yields four seeds, and genetic analysis confirmed that marker loci segregate in a 2:2 ratio within these tetrads. These mutations allow tetrad analysis to be performed in Arabidopsis and define steps in pollen cell wall development.
Arabidopsis↗
Large electrical currents traverse growing pollen tubes.
Using a newly developed vibrating electrode, we have explored the electric fields around lily pollen germinating in vitro. From these field measurements, we infer that each weeted pollen drives a steady current of a few hundred picoamperes through itself. Considered as a flow of positive ions, this current enters an ungerminated grain's prospective growth site and leaves it opposite end. After a grain germinates and forms a tube, this current enters most of the growing tube and leaves the whole grain. The current densities over both of these extended surface regions are relatively uniform, and the boundary zone, near the tube's base, is relatively narrow. This current continues as long as the tube grows, and even continues when elongation, as well as cytoplasmic streaming, are blocked by 1 mug/ml of cytochalasin B. After a otherwise indistinguishable minority of tubes have grown to lengths of a millimeter or more, their current comes to include an endless train of discrete and characteristic current pulses as well as a steady component. These pulses are about 30s long, never overlap, recur every 60-100s, and seem to enter a region more restricted to be growing tip than the steady current's sink. In most ways, the current through growing lily pollen resembles that known to flow through focoid eggs.
Cytochalasin B↗
A reverse-sandwich ELISA for IgG antibody to a pollen allergen.
We have developed a reverse-type sandwich ELISA for measurement of IgG (+IgA) antibody to a major allergen of Sugi (Japanese cedar) pollens. In this assay, microplate wells were coated with the allergen proteins that had been dispersed in the presence of 0.5 mol/L NaCl and 20 micrograms/ml of bovine serum albumin, followed by addition of test serum, and then the biotinylated allergen. Beta-galactosidase-conjugated streptavidin was used for detection of the captured allergen, 4-methylumbelliferyl-beta-D-galactoside was used as the enzyme substrate, and fluorescence intensity of the product, 4-methylumbelliferone, was measured by a fluorometric reader. This assay was found to detect a total activity of IgG, IgA, and IgE antibodies present in the serum of the patients with pollinosis. IgG (+IgA) antibody was determined after absorption of the serum with anti-IgE Sepharose gel. Sera from individuals who were unexposed to the pollens demonstrated no nonspecific reactions in this assay. This method may be useful as a simple technique for monitoring the efficacy of immunotherapy that is expected to elicit IgG blocking antibody and also for large-scale seroepidemiologic studies on the prevalence of non-IgE antibodies in a general population.
Allergens↗
Distribution of flower morphs, ploidy level and sexual reproduction of the invasive weed Oxalis pes-caprae in the western area of the Mediterranean region.
BACKGROUND AND AIMS: Oxalis pes-caprae is a widespread invasive weed in regions with a Mediterranean climate. In its native habitat (southern Africa) this species has been reported as heterostylous with trimorphic flowers and a self- and morph-incompatible reproductive system. In most of the areas invaded, only a pentaploid short-styled morphotype that reproduces mainly asexually by bulbils is reported, but this has only been confirmed empirically. This study aims to analyse the floral morph proportions in a wide distribution area, test the sexual female success, and explain the causes of low sexual reproduction of this species in the western area of the Mediterranean Basin. METHODS: Fifty-five populations of O. pes-caprae were sampled in the Iberian Peninsula and Morocco to evaluate the floral morph ratio and individual fruit set. In plants from a dimorphic population, hand-pollination experiments were performed to evaluate the effect of the pollen source on pollen tube growth through the style. The ploidy level and genome size of individuals of each floral morph were analysed using flow cytometry. KEY RESULTS: From the populations studied 89.1 % were monomorphic, with most of them containing the short-styled (SS) floral morph, and 10.9 % were dimorphic containing long-styled (LS) and SS morphs. In some of these, isoplethy was verified but no fruit production was observed in any population. A sterile form was also recorded in several populations. Hand-pollination experiments revealed that pollen grains germinated over recipient stigmas. In intermorph crossings, pollen tubes were able to develop and fruit initiation was observed in some cases, while in intramorph pollinations, pollen tube development was sporadic and no fruit initiation was observed. All individuals within each floral form presented the same DNA ploidy level: SS plants were pentaploid and LS and the sterile form were tetraploid. CONCLUSIONS: The low or null sexual reproduction success of this species in the area of invasion studied seems related with the high frequency of monomorphic populations, the unequal proportion of floral morphs in dimorphic populations and the presence of different ploidy levels between SS and LS morphs. The discovery of the occurrence of an LS floral morph and a sterile form, whose invading capacity in these areas is as yet unknown, will be valuable information for management programmes.
Flow Cytometry↗
RTS, a rice anther-specific gene is required for male fertility and its promoter sequence directs tissue-specific gene expression in different plant species.
A tapetum-specific gene, RTS, has been isolated by differential screening of a cDNA library from rice panicles. RTS is a unique gene in the rice genome. RNA blot analysis and in situ hybridization indicates that this gene is predominantly expressed in the anther's tapetum during meiosis and disappears before anthesis. RTS has no introns and encodes a putative polypeptide of 94 amino acids with a hydrophobic N-terminal region. The nucleotide and deduced amino acid sequence of the gene do not show significant homology to any known sequences. However, a sequence in the promoter region, GAATTTGTTA, differs only by one or two nucleotides from one of the conserved motifs in the promoter region of two pollen-specific genes of tomato. Several other sequence motifs found in other anther-specific promoters were also identified in the promoter of the RTS gene. Transgenic and antisense RNA approaches revealed that RTS gene is required for male fertility in rice. The promoter region of RTS, when fused to the Bacillus amyloliquefaciens ribonuclease gene, barnase, or the antisense of the RTS gene, is able to drive tissue-specific expression of both genes in rice, creeping bentgrass (Agrostis stolonifera L.) and Arabidopsis, conferring male sterility to the transgenic plants. Light and near-infrared confocal microscopy of cross-sections through developing flowers of male-sterile transgenics shows that tissue-specific expression of barnase or the antisense RTS genes interrupts tapetal development, resulting in deformed non-viable pollen. These results demonstrate a critical role of the RTS gene in pollen development in rice and the versatile application of the RTS gene promoter in directing anther-specific gene expression in both monocotyledonous and dicotyledonous plants, pointing to a potential for exploiting this gene and its promoter for engineering male sterility for hybrid production of various plant species.
Amino Acid Sequence↗
[Cupressaceae hay fever].
Cypress allergy or rather Cupressaceae allergy is an extraordinary observation subject and study model. Annual R.N.S.A. meeting is a good opportunity to share the analysts and sentinel doctors' point of view on this subject. For the medicine sentinel of the Nîmes's pollen site, the development of these Cupressaceae sensitivities is becoming a true public health priority. This feeling is shared by the southern sector responsible of the French network. It is absolutely necessary to develop actions.
France↗
Profilin is associated with the plasma membrane in microspores and pollen.
In higher plants, a large number of isoforms for the actin monomer-binding protein profilin have been identified, whereas other organisms express only few profilins. Furthermore, plant profilin isoforms are expressed in a tissue-specific manner. These observations raise questions concerning functional and locational differences between isoforms of plant profilins. In this paper, we introduce three polyclonal antisera and one monoclonal antibody developed against purified pollen profilins from Zea mays and against recombinant maize profilin. Immunoblot analyses of native profilins and four recombinant maize pollen profilin isoforms show that three of the antibodies display a preference for certain isoforms. In situ immunofluorescence of pollen of Zea mays and two developmental stages of microspores of Betula pumila indicates that all antibodies label plasma membrane-associated domains. Thus, we show that at least some profilin isoforms are located at a distinct subcellular domain within developing microspores and, less distinctly, in mature pollen. This contrasts previously reported uniform distributions throughout the cytoplasm of mature pollen and pollen tubes. The results are discussed in light of the large number of profilins co-expressed in plants and with reference to accumulating evidence for functional differences between profilin isoforms.
Animals↗
TRANSPARENT LEAF AREA1 encodes a secreted proteolipid required for anther maturation, morphogenesis, and differentiation during leaf development in maize.
We report the identification and functional analysis of TRANSPARENT LEAF AREA1 (TLA1), a maize (Zea mays) gene representing a novel class of secreted, extremely hydrophobic peptides (proteolipids) with a C-terminal Caax box-like motif. ZmTLA1 encodes 27 amino acid residues and is most strongly expressed in the egg cell and microspores. Lower transcript amounts were detected during vegetative development. Transgenic maize expressing an antisense transcript displayed a variety of phenotypes. The most visible phenotypes were dwarfism and transparent leaf areas resulting from defective morphogenesis of mesophyll, bundle sheath, stomatal, and epidermal cells during leaf development. Incomplete cell walls were observed, indicating a defect of cytokinesis. The accumulation of gerontoplasts was probably a secondary effect caused by defects of leaf cell morphogenesis. A defect of anther maturation was observed in approximately 30% of the plants displaying the tla phenotype. Male sterility was mainly caused by incomplete disintegration of the tapetal cell layers and tetrad callose as 90% of the microspores developed into functional pollen. Overexpression of ZmTLA1 seemed to have a lethal effect both in maize and Arabidopsis thaliana. Development of primary roots, root hairs, primary leaves, and chloroplasts was suppressed in Arabidopsis seedlings expressing an inducible ZmTLA1-green fluorescent protein (GFP) fusion protein. GFP signals were exclusively detected in cell walls. Based on our observations, we suggest that the ZmTLA1 peptide represents a class of novel plant morphogens required for the development and maturation of leaf and reproductive tissues.
Amino Acid Sequence↗
[Preliminary Studies on the Relationship Between Meiosis of Pollen Mother Cells and Pollen Abortion of Aloe arboresense Mill.].
The main reason for pollen abortion in Aloe arboresens Mill. was studied through the observation of meiosis and the microspore development of its pollen mother cells(PMCs). There are 14 chromosomes in the PMC of Aloe arboresens Mill., containing four pairs of long chromosomes and three pairs of short ones, and this karyotype belongs to dichotocarpism. Abnormalities observed were fallen into four categories:(1) Univalents, they were caused by failure in pairing, asynapsis and precocious cancellation of terminal chiasma. Oriented univalent pair was distributed at two poles normally in anaphase, while non-oriented univalent pair only at one pole. Another factor leading to univalents was that chromosomes were paired but without substantial exchange. (2) Multivalents. They might be produced by translocation heterozygote.(3) Chromosome bridges. There were three kinds of bridges in anaphase I and anaphase II: single and double chromosome bridge as well as "diagonal bridge".(4) A few cells were found with lagged chromosomes, micronuclei and unbalanced segregation of the chromosomes. In the later stages of meiosis, well-spread chromosomal configurations were rare because of the extremely sticky nature of the chromosome. The number and ratio of abnormalities were analysed and the relationship between abnormalities and pollen sterility were discussed. It is concluded that the sticky nature of the chromosome is the main reason for abnormal meiosis of Aloe arboresens Mill.PMC and pollen sterility. More than 90% of matured pollen grains were sterile.
Aloe↗
Development of an improved medium for germination of Cajanus cajan (L.) Millsp. pollen in vitro.
A simple, reliable medium for pollen germination of Cajanus cajan was developed by modifying Brewbaker and Kwack (BK) medium. Past attempts of C. cajan pollen germination in artificial media were not successful. A medium containing polyethylene glycol 4000 (PEG) showed more than 90% germination for C. cajan var. Pusa 33 only when the young buds (36 h before anthesis) were kept in pollen germination medium (PGM) for 36 h before pollen extraction. Supplementation of PGM with epsilon-amino caproic acid (EACA), an amino acid, showed improved pollen germination in Pusa 33 and also helped to avoid preconditioning of young buds before pollen extraction. It was also observed that there is a genotypic difference in the level of EACA required for in vitro pollen germination. Thus a complete medium for C. cajan genotypes consists of 37.5% sucrose+ 15% PEG 4000+250 mg l(-1) boric acid+300 mg l(-1) calcium nitrate+100 mg l(-1) potassium nitrate+ 200 mg l(-1) magnesium sulphate+1% agar+EACA (0, 100, 250, 500, 750 or 1000 mg l(-1)).
Culture Media↗
Nasal hyperresponsiveness to histamine induced by repetitive exposure to cedar pollen in guinea-pigs.
Nasal hyperresponsiveness is one of the characteristic features of the pathogenesis of allergic rhinitis. This study examined whether repetitive inhalation of antigen (Japanese cedar pollen) led to the development of nasal hyperresponsiveness to histamine in sensitized conscious guinea-pigs. Guinea-pigs were repeatedly challenged by pollen inhalation once every week following sensitization by means of intranasal application of pollen extract plus aluminium hydroxide. The upper airways obstruction (increase in specific airway resistance (sRaw)) in response to intranasally instilled histamine was measured as an index of nasal (hyper)responsiveness. The hyperresponsiveness to histamine gradually developed with repeated pollen inhalation challenge, and the airway response at the 20th and 24th challenges was three to four orders of magnitude higher than that in nonsensitized animals. Similar degrees of hyperresponsiveness were observed at 10 h and 2 days after a pollen inhalation challenge, but the hyperresponsiveness had almost disappeared by day 7. The increased responsiveness was suppressed by pretreatment with mepyramine but not with atropine. The maximum sRaw, which was observed 10 min after histamine instillation, was largely blocked by naphazoline. Hyperresponsiveness was hardly observed on methacholine instillation. The present allergic rhinitis model, showing marked nasal hyperresponsiveness to histamine after repeated intranasal allergen challenge in guinea pigs, should be useful for investigating the pathogenesis of allergic rhinitis.
Administration, Inhalation↗
The effect of heat stress on tomato pollen characteristics is associated with changes in carbohydrate concentration in the developing anthers.
Continuous exposure of tomato 'Trust' to high temperatures (day/night temperatures of 32/26 degrees C) markedly reduced the number of pollen grains per flower and decreased viability. The effect of heat stress on pollen viability was associated with alterations in carbohydrate metabolism in various parts of the anther during its development. Under control, favourable temperature conditions (28/22 degrees C), starch accumulated in the pollen grains, where it reached a maximum value 3 d before anthesis; it then diminished towards anthesis. During anther development, the concentration of total soluble sugars gradually increased in the anther walls and in the pollen grains (but not in the locular fluid), reaching a maximum at anthesis. Continuous exposure of the plants to high temperatures (32/26 degrees C) prevented the transient increase in starch concentration and led to decreases in the concentrations of soluble sugars in the anther walls and the pollen grains. In the locular fluid, however, a higher soluble sugar concentration was detected under the high-temperature regime throughout anther development. These results suggest that a major effect of heat stress on pollen development is a decrease in starch concentration 3 d before anthesis, which results in a decreased sugar concentration in the mature pollen grains. These events possibly contribute to the decreased pollen viability in tomato.
Carbohydrate Metabolism↗
Evaluation of serum specific IgE and skin responsiveness to allergenic extracts of Oleaceae pollens (Olea europaea, Fraxinus excelsior and Ligustrum vulgare) "in patients with respiratory allergy.
In the last few years an increasing interest for Olea europaea (O.e.) pollen has been developed in many countries. Several authors have studied the aerobiological, allergenic, epidemiological and clinical features of this pollinosis. The aim of our study was to evaluate cutaenous and serological responses to other oleaceae pollens allergens (Ligustrum vulgare (L.v.) and Fraxinus excelsior (F.e.) in patients with skin positivity to Olea europaea pollen extract. Twenty-three atopic rhinitis and/or asthmatic patients living in Naples area and with immediate positive skin reaction only to O.e. pollen extract were examined. Patients were tested by skin prick test (SPT) for O.e., F.e. and L.v. with glycerinated allergenic extracts. Serum enzyme immunoassay for the same allergens was also performed. We found a statistically significant correlation between the results of SPT and of specific IgE assay for Oleaceae pollens as well as between the results of the in vivo vs in vitro tests. We suggests the utility, in patients with O.e. pollinosis who travel in Northern europe, to plan SPT and/or specific IgE determinations also with F.e. and L.v. allergenic extracts for the possibility of developing a nasal and/or bronchial symptomatology after the inhalation of these pollen grains.
Adolescent↗
[Expression activity of maize Ubi-1 promoter in fertile transgenic maize plants].
The encoding sequence of gus gene from Escherichia coli was fused with maize Ubi-1 promoter and was introduced into maize genome via particle bombardment. Fertile transgenic maize plants were regenerated from bombarded type-I calluses which were derived from scutellar tissue of immature embryos based on PPT selection. Expression activity of gus gene under the control of Ubi-1 promoter was analysed using histochemical method, and the results showed that gus gene expressed in most tissues except anther. Ubi-GUS expression in pollen, egg cell and T1 immature embryos revealed that this promoter was active in early stages of plant development. Histochemically stained pollen grains of T0 plants showed a 1:1 segregation of the gus gene, which suggested that the foreign gene was inherited in Mendelian model in these plants. In addition, maize Ubi-1 promoter could reduce the copy number of foreign genes in transgenic maize plants, which might be useful in avoidance of gene silencing. T1 seeds have been harvested.
Blotting, Northern↗
Relationship between the time of birth and the development of immediate hypersensitivity to grass-pollen antigens.
Eighty-six children aged three to 14 years were skin-tested for immediate hypersensitivity to antigens which are seasonal (grass pollens) or non-seasonal (car, dog, house-dust mite) in occurrence. Children who reached the age of three months during a time of environmental exposure to grass pollen demonstrated a significantly increased incidence of immediate hypersensitivity reactions to three grass pollens, as compared with children born at other times of the year. No significant difference was found in their reactions to the non-seasonal antigens. These findings indicate a relationship between the time of birth and the subsequent development of immediate hypersensitivity in childhood. It is suggested that infants are particularly susceptible to sensitization when presented with antigen around three months of age.
Adolescent↗
TETRASPORE encodes a kinesin required for male meiotic cytokinesis in Arabidopsis.
A key step in pollen formation is the segregation of the products of male meiosis into a tetrad of microspores, each of which develops into a pollen grain. Separation of microspores does not occur in tetraspore (tes) mutants of Arabidopsis thaliana, owing to the failure of male meiotic cytokinesis. tes mutants thus generate large 'tetraspores' containing all the products of a single meiosis. Here, we report the positional cloning of the TES locus and details of the role played by the TES product in male cytokinesis. The predicted TES protein includes an N-terminal domain homologous to kinesin motors and a C-terminus with little similarity to other proteins except for a small number of plant kinesins. These include the Arabidopsis HINKEL protein and NACK1 and two from tobacco (Nishihama et al., 2002), which are involved in microtubule organization during mitotic cytokinesis. Immunocytochemistry shows that the characteristic radial arrays of microtubules associated with male meiotic cytokinesis fail to form in tes mutants. The TES protein therefore is likely to function as a microtubule-associated motor, playing a part either in the formation of the radial arrays that establish spore domains following meiosis, or in maintaining their stability.
Alleles↗
Investigation of short-range cedar pollen forecasting.
Pollen forecasting is of increasing interest as a way to help the general public avoid contact with allergy-inducing pollen. It was recently reported that the dynamics underlying pollen concentration series is very similar to that of low-dimensional deterministic chaos, thus opening up new avenues of development in local pollen forecasting. Our analysis of hourly cedar pollen series for two seasons showed evidence of a small degree of determinism underlying the pollen time-series dynamics. However, we could not confirm that our pollen series was generated by a low-dimensional chaotic system. The nearest-neighbor method using local constant prediction applied to hourly pollen forecasting with a 1-h lead time was effective for small to medium pollen variations, but failed to reproduce large and intermittent pollen bursts. The performance of the nearest-neighbor model was significantly improved by applying a nonlinear filter to the source dataset. Standard time-series techniques such as neural networks did not improve upon these results. The difficulty in fully characterizing and accurately forecasting the pollen series was thought to originate in the nonstationarity of the series and in the large and intermittent pollen bursts that were found to have no apparent time structure. Thus the dynamics of hourly pollen series is probably not strongly tied to a low-dimensional chaotic system.
Journal Article↗