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At least 973 records · Page 54Linked to original sources
PubMed2006

RPA, a class II ARFGAP protein, activates ARF1 and U5 and plays a role in root hair development in Arabidopsis.

The polar growth of plant cells depends on the secretion of a large amount of membrane and cell wall materials at the growing tip to sustain rapid growth. Small GTP-binding proteins, such as Rho-related GTPases from plants and ADP-ribosylation factors (ARFs), have been shown to play important roles in polar growth via regulating intracellular membrane trafficking. To investigate the role of membrane trafficking in plant development, a Dissociation insertion line that disrupted a putative ARF GTPase-activating protein (ARFGAP) gene, AT2G35210, was identified in Arabidopsis (Arabidopsis thaliana). Phenotypic analysis showed that the mutant seedlings developed isotropically expanded, short, and branched root hairs. Pollen germination in vitro indicated that the pollen tube growth rate was slightly affected in the mutant. AT2G35210 is specifically expressed in roots, pollen grains, and pollen tubes; therefore, it is designated as ROOT AND POLLEN ARFGAP (RPA). RPA encodes a protein with an N-terminal ARFGAP domain. Subcellular localization experiments showed that RPA is localized at the Golgi complexes via its 79 C-terminal amino acids. We further showed that RPA possesses ARF GTPase-activating activity and specifically activates Arabidopsis ARF1 and ARF1-like protein U5 in vitro. Furthermore, RPA complemented Saccharomyces cerevisiae glo3Delta gcs1Delta double mutant, which suggested that RPA functions as an ARFGAP during vesicle transport between the Golgi and the endoplasmic reticulum. Together, we demonstrated that RPA plays a role in root hair and pollen tube growth, most likely through the regulation of Arabidopsis ARF1 and ARF1-like protein U5 activity.

ADP-Ribosylation Factor 1↗
PubMed2002

Sensitization of mice with olive pollen allergen Ole e 1 induces a Th2 response.

BACKGROUND: Olive pollen is one of the main causes of allergy in Mediterranean countries, where it is widely distributed. One inconvenience in studying new immunotherapies for olive pollen allergy is the lack of suitable animal models. The aim of this study was to develop a murine model of IgE sensitization to Ole e 1, the major allergen of olive pollen, which mimics the immunological features of olive pollinosis in humans and to investigate the in vivo antigenicity of the recombinant form of the allergen. METHODS: BALB/c mice were sensitized by intraperitoneal administration of natural Ole e 1 (nOle e 1) and recombinant Ole e 1 (rOle e 1) in Al(OH)(3), respectively. Serum levels of specific IgE, IgG1 and IgG2a, cytokine production and the proliferative response of splenocytes after in vitro stimulation with nOle e 1 were analyzed by ELISA and flow cytometry. The binding capacity of rOle e 1-specific IgG1 was examined by ELISA and immunoblotting. RESULTS: Sensitization with nOle e 1 or rOle e 1 induced high levels of specific IgE and IgG1 versus low IgG2a antibody levels. Splenocytes from sensitized mice exhibited a proliferative response to nOle e 1. In vitro stimulated splenic cells from nOle e 1-primed mice produced IL-4 and low or nondetectable levels of IFN-gamma. Specific IgE and IgG1 antibodies of immunized mice bound to the same Ole e 1 isoforms and showed a similar degree of cross-reactivity as observed for human IgE. Mouse specific nOle e 1 IgG1 was strongly inhibited by IgE from allergic patients. The IgG1 antibodies elicited by rOle e 1 reacted with both the recombinant and natural forms of the allergen. CONCLUSIONS: A murine model of Ole e 1 sensitization has been established. rOle e 1 shows similar allergenicity and antigenicity to its natural form. This model should provide a useful tool for evaluating antigenic molecules and exploring new therapeutic approaches in order to treat IgE-mediated olive pollinosis.

Allergens↗
PubMed2002

SEMAPHORE1 functions during the regulation of ancestrally duplicated knox genes and polar auxin transport in maize.

The expression of class 1 knotted1-like homeobox (knox) genes affects numerous plant developmental processes, including cell-fate acquisition, lateral organ initiation, and maintenance of shoot apical meristems. The SEMAPHORE1 gene product is required for the negative regulation of a subset of maize knox genes, the duplicated loci rough sheath 1 and gnarley1 (knox4). Recessive mutations in semaphore1 result in the ectopic expression of knox genes in leaf and endosperm tissue. Genetic analyses suggest that SEMAPHORE1 may regulate knox gene expression in a different developmental pathway than ROUGH SHEATH2, the first-identified regulator of knox gene expression in maize. Mutations at semaphore1 are pleiotropic, disrupting specific domains of the shoot. However, unlike previously described mutations that cause ectopic knox gene expression, semaphore1 mutations affect development of the embryo, endosperm, lateral roots, and pollen. Moreover, polar transport of the phytohormone auxin is significantly reduced in semaphore1 mutant shoots. The data suggest that many of the pleiotropic semaphore1 phenotypes result from defective polar auxin transport (PAT) in sem1 mutant shoots, and support models correlating down-regulated knox gene expression and PAT in maize shoots.

Gene Expression Regulation, Developmental↗
PubMed2001

[Asthma and allergy].

Allergy is routinely taken into account in asthma. The allergic reaction is based on Th2 lymphocytes specific to the allergen, which induce production of E immunoglobulins (IgE) and activation of eosinophils. In atopic asthma, domestic allergens are more often responsible than pollen. They play a part early in the development of the disorder, and subsequently as factors triggering exacerbations. Work-related asthma should always be suspected. History-taking should seek the relevance of allergens in the clinical manifestations, confirmed by skin tests, and if necessary assessment of specific IgE. Provocation tests should be used only diagnosis of work-related asthma. Removal of allergens should be suggested. Specific desensitisation may be indicated in order to decrease high-dosage drug treatment. Rhinologic treatment is part of patient management. Treatments being developed include the use of anti-IgE antibodies, anti-interleukin (IL)-5, soluble IL-4 receptors and recombinant allergens.

Allergens↗
PubMed1988

[Antihistaminic or anti-degranulating activity of pregnancy serum].

From observation of women who had anaphylactic accidents to hymenoptera venoms, with positive histamine release, we have noticed that these same patients lose their histamine release during pregnancy. Measurement of histamine release to pollens confirms the existence of a histaminase, which develops from the third month of the pregnancy and which is the origin of the loss of histamine release. This study makes eliminates a possible anti-degranulation ability of pregnancy sera.

Amine Oxidase (Copper-Containing)↗
PubMed1983

Pharmacological modulation of bronchial hyperreactivity.

The airways of asthmatics are hyperreactive, not only to allergens but to a wide range of non-specific physical and chemical stimuli. Four mechanisms which have been proposed to be causes of hyperreactivity are (i) a decrease in baseline airway calibre (ii) an increase in the responsiveness of the bronchial smooth muscle (iii) an imbalance in the autonomic neurophysiological regulation of airway calibre and (iv) epithelial changes which lead to an increase in the accessibility of allergens and non-specific stimuli to the mast cells, sensory nerve endings or bronchial smooth muscle beneath the airway mucosa. We have studied the effects of some of the proposed mediators of asthma on lung mechanics and irritant receptor activity in dogs with a respiratory tract infection and in dogs following exposure to SO2 gas at a concentration (400 ppl) sufficient to damage the airway epithelium (Jackson and Richards, 1980). In dogs naturally infected with Bordetella bronchiseptica there was an increased airway reactivity to histamine which was almost completely abolished by vagotomy. The hyperreactivity to histamine was shown to be due to an increased responsiveness of lung irritant receptors. In dogs exposed to SO2 gas changes in RL induced by 5-hydroxytryptamine or electrical stimulation of the vagus nerves were significantly increased when compared to the responses in normal dogs. Altounyan (1970) has shown that continuous exposure to allergens in patients with seasonal allergic asthma also leads to an increase in non-specific bronchial reactivity. Pharmacological modulation of airway reactivity can be divided into the acute and long term effects of drugs. Acute effects of drugs have been studied by several groups of workers using the airway responses to inhalation of various non-specific stimuli (e.g. distilled water, cold air, SO2 gas). Beta-stimulants and sodium cromoglycate are usually effective inhibitors and anticholinergic drugs are effective when a reflex component contributes to the bronchoconstriction. Few controlled studies of the effect of long-term treatment with drugs on bronchial hyperreactivity have been carried out although as early as 1970 Altounyan showed that long-term treatment with sodium cromoglycate could inhibit the development of non-specific hyperreactivity during the pollen season in pollen-sensitive asthmatics. A number of further studies have confirmed these early observations.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1998

BRASSINOSTEROIDS: Essential Regulators of Plant Growth and Development.

Brassinosteroids (BRs) are growth-promoting natural products found at low levels in pollen, seeds, and young vegetative tissues throughout the plant kingdom. Detailed studies of BR biosynthesis and metabolism, coupled with the recent identification of BR-insensitive and BR-deficient mutants, has greatly expanded our view of steroids as signals controlling plant growth and development. This review examines the microchemical and molecular genetic analyses that have provided convincing evidence for an essential role of BRs in diverse developmental programs, including cell expansion, vascular differentiation, etiolation, and reproductive development. Recent advances relevant to the molecular mechanisms of BR-regulated gene expression and BR signal transduction are also discussed.

Journal Article↗
PubMedDate not supplied

Differences in pollen-tube growth rate and reproductive isolation between Louisiana irises.

A level of reproductive isolation is necessary for the process of genetic divergence. Such isolation also prevents the homogenization of species following secondary contact. This study is an investigation of the relative contribution of two prefertilization mechanisms, pollen-tube growth rate and pollen-tube attrition, to the reproductive isolation of Iris fulva and I. brevicaulis, two naturally hybridizing members of the Louisiana iris species complex. Flowers of each species were first pollinated with heterospecific pollen. After various time intervals, conspecific pollen was added. Analyses of the patterns of resulting progeny were used to infer whether relative pollen-tube growth rates act as a prefertilization isolating mechanism. In I. fulva the frequency of hybrid seeds increased with increasing pollination interval, suggesting that hybridization is limited by pollen-tube growth rates. Likewise, in I. brevicaulis hybrid sed production increased, but it was high regardless of the pollination interval. Thus it appears that relative pollen-tube growth rates limit interspecific reproduction in both species, but barriers are weaker in I. brevicaulis.

Genotype↗
PubMed1997

Characterization of a lily tapetal transcript that shares sequence similarity with a class of intracellular pathogenesis-related (IPR) proteins.

This study addresses isolating and characterizing a cDNA clone corresponding to a tapetum-specific transcript, designated as PR-10a from Lilium longiflorum. Anther ontogeny is histologically divided into three consecutive phases. The first encompasses early proliferative stages and differentiation of the locules. The second concerns microspore development from the onset of meiosis through microspore maturation. The final phase involves pollen maturation, originating with microspore mitosis through pollen formation. The lily PR-10a transcript is anther-specific and temporally expressed only at the phase of microspore development during which the tapetal cells become polarized, highly secretory, and exhibit loss of cell walls. The maximal level of PR-10a transcript coincides strictly with the peak of tapetal secretory function. Comparing mRNA and cDNA insert sizes reveals that PR-10a is close to full-length. Sequence analysis demonstrates similarity between the predicted lily PR-10a and asparagus AoPR1 protein, potato pSTH2 and pSTH21 proteins, parsley PcPR1 and PcPR3 proteins, bean PvPR1 and PvPR2 proteins, lupin L1R18B protein, pea 149 protein and a family of major allergens including Cor a 1 of hazel, Car b 1 of hornbeam, Aln g 1 of alder, Bet v 1 of birch and Api g 1 of celery. To the authors' knowledge, this is the first reported organ/tissue-specific IPR protein.

Amino Acid Sequence↗
PubMed2003

Histological study of post-pollination events in Spathodea campanulata beauv. (Bignoniaceae), a species with late-acting self-incompatibility.

The reproductive biology of Spathodea campanulata was investigated by means of hand-pollination experiments, observations of pollen tube growth using fluorescence microscopy, and serial sections of ovules in selfed and crossed pistils. Only cross-pollinated flowers developed fruits, and all selfed flowers abscised within 3-4 d. However, self pollen tubes grew successfully to the ovary, penetrating and fertilizing the majority of ovules by 48 h, indicating that S. campanulata is a species with late-acting self-incompatibility. The incidences of ovule penetration, fertilization and endosperm initiation were all significantly slower in selfed vs. crossed pistils, although no other signs of malfunctioning were detected. The possible role of such slow self pollen tube effectiveness as a recognition event is discussed within the context of the slow but not entirely suppressed self pollen tube growth reported for some species with conventional homomorphic self-incompatibility.

Bignoniaceae↗
PubMed1992

Purification and characterization of actin from maize pollen.

Pollen is an excellent source of actin for biochemical and physiological studies of the actomyosin system in higher plants. We have developed an efficient method to prepare relatively high levels of actin from the pollen of maize (Zea mays L.). The procedures of purification include acetone powder preparation, saturated ammonium sulfate fractionation, diethylaminoethyl-cellulose chromatography, a cycle of polymerization-depolymerization, and Sephacryl S-200 gel filtration. The average yield of actin is 19 milligrams per 100 grams of pollen grains extracted. This is comparable with those of Acanthamoeba castellanii and human platelets. The purified pollen actin is electrophoretically homogeneous and its molecular mass is 42 kilodaltons. The amino acid composition and circular dichroism spectrum of pollen actin are identical to those of muscle actin. The actin purified from pollen is able to polymerize to F-actin. The pollen F-actin activated the activity of the muscle myosin ATPase sevenfold.

Journal Article↗
PubMed1993

Allergenic cross-reactivity between Parthenium and ragweed pollen allergens.

Cross-reactivity of allergens from the pollen of the Compositae weeds, Parthenium hysterophorus (American feverfew) and Ambrosia (ragweed), in 2 groups of patients with different geographic distributions was studied. Parthenium-sensitive Indian patients, who were never exposed to ragweed, elicited positive skin reactions with ragweed pollen extracts. A significant correlation in the RAST scores of Parthenium and ragweed-specific IgE was observed with the sera of Parthenium and ragweed-sensitive Indian and US patients, respectively. RAST inhibition experiments demonstrated that the binding of IgE antibodies in the sera of ragweed-sensitive patients to short (W1) and giant (W3) ragweed allergen discs could be inhibited by up to 94% by Parthenium pollen extracts. Similar inhibition (up to 82%) was obtained when the sera of Parthenium rhinitis patients were incubated with ragweed allergen extracts. A dose-dependent proliferation of lymphocytes from a Parthenium-sensitive rhinitis patient with elevated levels of both Parthenium and ragweed-specific IgE was observed when incubated with Parthenium and ragweed pollen extracts. A 1.6-fold higher proliferation, however, was observed with Parthenium pollen extract at a concentration of 100 micrograms/ml. These results suggest that shared epitopes present on Parthenium and ragweed pollen allergens are recognized by both Indian and US patients sensitized by exposure to Parthenium and ragweed pollen, respectively. The high degree of cross-reactivity between Parthenium and ragweed pollen allergens suggests that individuals sensitized to Parthenium may develop type-I hypersensitivity reactions to ragweed and vice versa when they travel to regions infested with the weed to which they had not been previously exposed.

Adult↗
PubMed2000

Pathogenesis of allergic diseases: interactions between pollutants and pollens really important?

Nowadays, the prevalence of atopic diseases in so-called developed countries is estimated to exceed 30%. Furthermore, it may reach over 50% in two generations. Based on such facts, the so-called "atopic predisposition" can not be defined as an abnormal genotype consisting of certain "atopic gene(s)" possessed by a minority of unfortunate people. Rather, the gene(s) that cause atopic diseases reside in the common human gene repertoire, and several environmental factors would cause the overexpression of some constitutive gene(s), leading to the development of atopic diseases. The author considers that overexpression and production of Th2 cytokines, especially IL-5, may be a key event. The recent prevalence of atopic diseases in developed countries may be mediated by a change of Th2 polarization due to modern retrogression of environmental factors such as bacterial and viral infections that favor Th1 polarization. The "atopic trait" might be actually an "atopic phenotype" rather than an "atopic genotype". In other words, the atopic trait seems not to be a genotype that decides the development of an atopic disease on an all or nothing basis, but a phenotype that determines the susceptibility to the disease. Of course, the familial nature of atopic diseases is undeniable, but this does not necessarily indicate the genetic nature of atopic diseases. For example, if a parent suffers from tuberculosis, the possibility that the children will develop tuberculosis markedly increased. However, tuberculosis is a truly infectious disease. In this article, several environmental factors those may affect the recent sharp increase of atopic diseases are discussed.

Air Pollution↗
PubMed2005

Stigma development and receptivity in almond (Prunus dulcis).

BACKGROUND AND AIMS: Fertilization is essential in almond production, and pollination can be limiting in production areas. This study investigated stigma receptivity under defined developmental stages to clarify the relationship between stigma morphology, pollen germination, tube growth and fruit set. METHODS: Light and scanning electron microscopy were employed to examine stigma development at seven stages of flower development ranging from buds that were swollen to flowers in which petals were abscising. Flowers at different stages were hand pollinated and pollen germination and tube growth assessed. Artificial pollinations in the field were conducted to determine the effect of flower age on fruit set. KEY RESULTS: Later stages of flower development exhibited greater stigma receptivity, i.e. higher percentages of pollen germination and more extensive tube growth occurred in older (those opened to the flat petal stage or exhibiting petal fall) than younger flowers. Enhanced stigma receptivity was associated with elongation of stigmatic papillae and increased amounts of stigmatic exudate that inundated papillae at later developmental stages. Field pollinations indicated that the stigma was still receptive and nut set was maintained in older flowers. CONCLUSIONS: Stigma receptivity in almond does not become optimal until flowers are past the fully open stage. The stigma is still receptive and fruit set is maintained in flowers even at the stage when petals are abscising. Strategies to enhance pollination and crop yield, including the timing and placement of honey bees, should consider the effectiveness of developmentally advanced flowers.

Flowers↗
PubMed2000

Crossing relationships among ancient and experimental sunflower hybrid lineages.

Reproductive barrier formation between newly derived hybrid taxa and their parental species represents a major evolutionary hurdle. Here, I examine the development of a sterility barrier during hybrid speciation by examining the fertility of progeny from all combinations of crosses involving three experimentally synthesized sunflower hybrid lineages, their natural hybrid counterpart, Helianthus anomalus, and their parents, H. annuus and H. petiolaris. Crosses between the parental species and H. anomalus generated almost completely sterile offspring (pollen viability < 5%; seed set < 1%). A fairly strong sterility barrier also has developed between three hybrid lineages and both parental species (pollen viability 11.1-41.6%; seed set 0.84-20.1%). In contrast, the three hybrid lineages are almost fully interfertile (pollen viabilities 83.1-88.6%; seed set 72.1-75.3%), as predicted by molecular mapping studies that indicate they have converged on a similar set of gene combinations and chromosomal rearrangements. A modest decline in compability is observed in crosses between the three hybrid lineages and H. anomalus (pollen viabilities 64.1-70.7%; seed set 37-43%), a result that agrees well with prior data demonstrating significant congruence between the genomes of the natural and experimental hybrid lineages. These observations not only indicate that reproductive isolation can arise as a by-product of fertility selection in hybrid populations, but also testify to the repeatability of this mode of speciation.

Breeding↗