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At least 541 records · Page 30Linked to original sources
PubMed2006

Distinct short-range ovule signals attract or repel Arabidopsis thaliana pollen tubes in vitro.

BACKGROUND: Pollen tubes deliver sperm after navigating through flower tissues in response to attractive and repulsive cues. Genetic analyses in maize and Arabidopsis thaliana and cell ablation studies in Torenia fournieri have shown that the female gametophyte (the 7-celled haploid embryo sac within an ovule) and surrounding diploid tissues are essential for guiding pollen tubes to ovules. The variety and inaccessibility of these cells and tissues has made it challenging to characterize the sources of guidance signals and the dynamic responses they elicit in the pollen tubes. RESULTS: Here we developed an in vitro assay to study pollen tube guidance to excised A. thaliana ovules. Using this assay we discerned the temporal and spatial regulation and species-specificity of late stage guidance signals and characterized the dynamics of pollen tube responses. We established that unfertilized A. thaliana ovules emit diffusible, developmentally regulated, species-specific attractants, and demonstrated that ovules penetrated by pollen tubes rapidly release diffusible pollen tube repellents. CONCLUSION: These results demonstrate that in vitro pollen tube guidance to excised A. thaliana ovules efficiently recapitulates much of in vivo pollen tube behaviour during the final stages of pollen tube growth. This assay will aid in confirming the roles of candidate guidance molecules, exploring the phenotypes of A. thaliana pollen tube guidance mutants and characterizing interspecies pollination interactions.

Arabidopsis↗
PubMed1999

The gene encoding tobacco gibberellin 3beta-hydroxylase is expressed at the site of GA action during stem elongation and flower organ development.

Gibberellin 3beta-hydroxylase catalyzes the final step in the biosynthetic pathway leading to the plant hormone gibberellin (GA) and, therefore, the in vivo localization of this enzyme should give a direct indication of the site of synthesis of bioactive GAs in plants. We have isolated a cDNA clone, Nty (Nicotiana tabacum GA 3beta-hydroxylase), which encodes a putative GA 3beta-hydroxylase, by RT-PCR using RNA from tobacco shoot apices. Functional analysis, using an NTY protein expressed in Escherichia coli, revealed that Nty encoded an active GA 3beta-hydroxylase. A high expression level of Nty was observed in shoot apices, flowers, roots, young internodes but not in leaves or seeds. We performed more detailed expression analyses using in situ hybridization and histochemical analyses of the GUS activity in transgenic tobacco plants carrying an Nty promoter:GUS fusion gene. These studies revealed that expression of Nty was restricted to specific regions, including actively dividing and elongating cells in the various organs; rib meristem and elongation zones of shoot apices, tapetum and pollen grains in developing anthers and root tips, which are consistent with the sites of GA action. It is proposed that GA actions depend on the modulation of endogenous bioactive GA levels through the regulation of GA 3beta-hydroxylase expression in situ.

Amino Acid Sequence↗
PubMed2003

[Development of new sensitizations to allergic components in birch pollen extract during specific immunotherapy].

Specific immunotherapy is the only currently available allergen-orientated treatment able to modify the natural history of respiratory allergic diseases. Safety and clinical efficacy of this treatment are well documented, but evidence about the ability to reduce new sensitizations is still poor. The authors describe the development of new IgE specificities to allergenic components in birch pollen extract during specific immunotherapy. A study was carried out in 12 birch pollen-sensitive patients who received injection immunotherapy for 6 months. Eight patients not submitted to SIT were used as a control. New IgE sensitizations to Bet v 2 developed in 25% of the birch immunotherapy-treated patients and the oral allergy syndrome additionally in one of them.

Allergens↗
PubMed2000

Sensitization to oilseed rape is not due to cross-reactivity with grass pollen.

BACKGROUND: Oilseed rape is an important crop grown in the UK which can cause specific immunological sensitization with clinical symptoms in a relatively small number of the general population. Individuals with immunoglobulin (Ig) E-mediated allergy to oilseed rape have also been found to be sensitized to other pollen allergens, most frequently being grass pollen. Cross-reactivity between common grass and oilseed rape would have important implications, especially as their flowering period coincides. OBJECTIVE: We have investigated whether the cosensitization found in individuals sensitized to both oilseed rape and grass pollen is due to cross-reactivity. METHODS: Cross-reactivity between oilseed rape and grass pollen was determined using RAST, RAST inhibition, Western blotting and inhibition studies with Western blotting. RESULTS: Competitive RAST inhibition studies between pollen of oilseed rape and grass failed to show any cross-reactivity between the pollen types. Self-inhibition with oilseed rape resulted in 90% inhibition, whereas there was less than 10% inhibition with grass pollen. Western blotting revealed allergens of similar molecular weight in both oilseed rape and grass pollen. Despite allergens of similar molecular weights being present in both pollen types, inhibition immunoblot studies confirmed that the allergens in the two allergens were immunologically distinct. CONCLUSION: The allergens of oilseed rape and grass pollen, although similar in molecular weights, are immunologically distinct and there is no evidence of cross-reactivity between them. Individuals allergic to grass pollen will not necessarily develop a specific nasal or airway response to inhaled oilseed rape pollens.

Adult↗
PubMed2004

Identification of candidate genes for in vitro androgenesis induction in maize.

Extensive studies have been conducted to understand the genetic control of in vitro androgenesis, but little is know about the genes and the mechanisms involved in the switch that allows an immature pollen grain to develop as an embryo. We have developed two maize isogenic lines with high androgenetic aptitude, named AH5-44 and AH5-49, through backcross and selection from a high-responsive DH229 line on the non-responding A188 line genetic background. The genomic structure of these two lines was precisely described with microsatellite markers. Five regions retained from the parent DH229 highly responsive to androgenesis were localised in both AH5-44 and AH5-49. Sequences expressed on microspores extracted from the four lines were amplified using a cDNA-AFLP protocol. For each line, eight culture conditions were compared: microspores extracted after tassel recovery, after 7 or 14 days in cold room and after 1-4 days of in vitro culture. This genetic and developmental screening allowed us to identify four sequences, including a new HSP70-like candidate gene. Possible implication of the identified sequences in androgenesis response is discussed.

Base Sequence↗
PubMed2000

[Studies of the development of Triticum aestivum-Leymus racemosus translocation lines by pollen irradiation].

Pollens of 94G15 and 94G45, two wheat lines added to chromosome Lr.14 and Lr.2 of Leymus racemosus respectively were irradiated via 60Co-gamma rays and then used to hybridize with two common wheat varieties--Yangmai 5 and Mianyang 11. The five plants showing chromosome pairing between T. aestivum and L. racemosus at PMC MI stage were selected from seventeen examined plants of M1 progeny as the result of meiosis configuration analysis of chromosomes treated with Giemsa C-banding and fluorescent in situ hybridization. Among which, two T. aestivum-L. racemosus alien translocation lines--LW8(3)1 and LW11(3)1 were developed on the basis of further identification of M2 RTC chromosomes by C-banding and in situ hybridization. In addition, feasibility and effectiveness of the pollen irradiation in the development of T. aestivum-relatives alien translocations and the availability of the translocation lines of T. aestivum-L. racemosus are also discussed.

Chromosome Banding↗
PubMed1991

Auxin-induced expression of the soybean GH3 promoter in transgenic tobacco plants.

The gene encoding the auxin-responsive GH3 mRNA (G. Hagen, A. Kleinschmidt, TJ. Guilfoyle, Planta 162: 147-153 (1984] from soybean was cloned, and its sequence and transcription initiation site were determined. The promoter of the GH3 gene has been fused to the open reading frame of the Escherichia coli uidA gene which encodes beta-glucuronidase (GUS). This fusion gene was introduced into tobacco via Agrobacterium tumefaciens-mediated transformation, and the expression of the gene was examined by fluorometric assay and histochemical staining of young R1 tobacco seedlings and mature plants. In transgenic tobacco plants that have not been exposed to exogenous auxin, expression of the fusion gene is largely restricted to roots of young green plants and developing floral organs, including ovules, developing seeds, and pollen, of mature plants. Application of exogenous auxin to tobacco seedlings or plant organs results in a greater than 50-fold increase in expression of GUS. Auxin-induced GUS expression is greatest in vascular tissue, but not restricted to this tissue. The auxin-deduced GUS expression was characterized for kinetics, auxin specificity and dose response.

Amino Acid Sequence↗
PubMed1999

Structure and regulation of the Arabidopsis thaliana allene oxide synthase gene.

Allene oxide synthase (AOS) is encoded by a single intronless gene in Arabidopsis thaliana (L.) Heynh. The promoter region of the AOS gene exhibits, in addition to the clements of a minimal promoter and the presence of general enhancers, cis-elements that, in other promoters, are responsible for stress- and ethyleneresponsiveness. Arabidopsis thaliana and Nicotiana tabacum L. were transformed with a chimaeric gene consisting of a 1.9-kb 5'-upstream sequence and the first 95 nucleotides of the AOS coding sequence translationally fused to uidA encoding beta-glucuronidase (GUS). Using histochemistry, GUS activity was seen in older leaves, in the bases of petioles and in stipules, during the early stages of carpel development, in maturing pollen grains and at the base of elongated filaments, as well as in abscission-zone scars. A role for jasmonates in floral organ abscission is suggested by these findings. Furthermore, the AOS promoter was activated both locally as well as systemically upon wounding. Jasmonic acid, 12-oxophytodienoic acid and coronatine strongly induced GUS activity. This induction remained confined to the treated leaf when agonists were applied locally to a leaf, suggesting that neither jasmonic acid nor 12-oxophytodienoic acid are physiologically relevant components of the systemic wound signal complex. Rather, the data show that jasmonates behave as local response regulators produced at or around the sites of action in response to appropriate triggers of their synthesis.

Arabidopsis↗
PubMed2003

Identification of an Arabidopsis mitochondrial succinate-fumarate translocator.

Complementation of a yeast acr1 mutant carrying a deletion of the succinate/fumarate carrier gene enabled functional identification of a mitochondrial succinate translocator from Arabidopsis thaliana (AtmSFC1). Thus complementation of yeast mutants is applicable also for identification and characterization of organellar transporters. Reverse transcription polymerase chain reaction and promoter-GUS fusion showed expression of AtmSFC1 in 2 day old dark grown seedlings, which declined in cotyledons during further development, consistent with a role in export of fumarate for gluconeogenesis during lipid mobilization at early germination of Arabidopsis seeds. In mature plants, expression was found in developing and germinating pollen, suggesting a role in ethanolic fermentation.

Amino Acid Sequence↗
PubMed1994

Isolation and microinjection of active sperm nuclei into egg cells and central cells of isolated maize embryo sacs.

Artificial fertilisation was attempted in maize by microinjecting sperm nuclei into the egg cell or central cell of isolated embryo sacs. A protocol for isolation of nuclei from pollen grains was developed and a pure fraction of sperm nuclei was obtained after centrifugation on a Percoll gradient. The in vitro transcriptional activity of the nuclei was tested by incorporation of radioactive UTP into RNA. The level of labelled nucleotide incorporation increased and reached a maximum after between 30 and 40 min in the incubation medium. The embryo sacs were enzymatically isolated and their viability determined by observation of cytoplasmic streaming in the female cells. The embryo sacs were immobilised by embedding in low-melting-point agarose and a single male nucleus was injected with a bevelled microcapillary. The presence of the injected nucleus in the egg or central cell was demonstrated using a cytological approach. This paper presents an alternative method for studying the intimate processes of fertilisation in plants.

Fertilization↗
PubMed1995

A novel Arabidopsis type 1 protein phosphatase is highly expressed in male and female tissues and functionally complements a conditional cell cycle mutant of Aspergillus.

Type 1 protein phosphatases are very highly conserved throughout eukaryotes where they regulate a number of key metabolic and morphogenetic processes. A cDNA, AtPP1bg, representing a new member of the type 1 protein phosphatase gene family in Arabidopsis has been isolated on the basis of hybridization with the Aspergillus bimG protein phosphatase gene. The AtPP1bg gene potentially encodes a 37 kDa protein very closely related to PP1 but with divergent N- and C-termini. The predicted amino acid sequence shows 71% identity to the ORF of the bimG gene. When expressed in Aspergillus under the alcA promoter, this phosphatase complements the temperature-sensitive bimG11 mutation allowing nearly normal vegetative growth at 37 degrees C (but not at 42 degrees C). Notably, the plant PP1 does not support morphogenesis (conidiation) at 37 degrees C. This may indicate that conidophore formation has particular phosphatase requirement(s) which the plant PP1 cannot supply. The pattern of expression of the AtPP1bg transcript has been studied during development of the plant. In situ hybridization of Arabidopsis with antisense probes shows that this phosphatase gene is expressed at a low level throughout the plant, but is strongly upregulated within developing flowers, especially in the tapetum, the developing and mature pollen and in the ovaries. This implies that the AtPP1bg either has a specialized role in the formation of these organs, or that there is an increased requirement for protein phosphatase 1 at these stages. It was found that the level of AtPP1bg transcript, as judged by the relative intensity of staining in different cells within the floral meristems, did not vary during the cell cycle.

Amino Acid Sequence↗
PubMed1997

The maize actin-depolymerizing factor, ZmADF3, redistributes to the growing tip of elongating root hairs and can be induced to translocate into the nucleus with actin.

The maize actin depolymerizing factor, ZmADF3, binds G- and F-actin, and increases in vitro actin dynamics. Polyclonal antibodies have been raised against ZmADF3 and these detect a single band of approximately 17 kDa in all maize tissues examined, with the exception of pollen. In the development of root hairs, the distribution of ZmADF3 is related to actin reorganization. In the early stages of hair development, ZmADF3 is distributed throughout the cytoplasm. As the hair emerges and the microfilament bundles redirect to the outgrowth there is a simultaneous redistribution of ZmADF3 which now concentrates at the tip of the emerging hair and remains in this position as elongation proceeds. These observations show that ZmADF3 localizes to a region where actin is being remodelled during tip growth. After cytochalasin D treatment which disrupts actin filaments, short rods of ZmADF3 and actin appear in the nucleus suggesting that ZmADF3 may function by guiding actin to sites of actin polymerization.

Actin Depolymerizing Factors↗
PubMed2002

The IRE gene encodes a protein kinase homologue and modulates root hair growth in Arabidopsis.

We identified an Arabidopsis mutant, incomplete root hair elongation (ire), whose root hairs are about 40% shorter than the wild type owing to the early cessation of their growth. In contrast, the hy5 mutant has root hairs about twice as long as the wild type, possibly because of delayed cessation of growth. Thus IRE and HY5 are likely to modify the duration of growth of root hairs. We cloned the IRE locus using the T-DNA tagged line. The IRE locus encodes a protein that includes a serine/threonine protein kinase domain. The primary structure of this kinase domain shows significant similarity to a group of protein kinases among various eukaryotes. In the Arabidopsis genome there are at least three genes that are closely related to IRE. The IRE transcript was detected in every organ examined. However, the IRE promoter-GUS fusion gene was strongly expressed in the elongating root hair cells, suggesting the cell-autonomous function of IRE in root hairs. GUS activity was also detected in pollen grains, which develop by tip growth, suggesting that IRE has a common role in the tip growth of plant cells.

Alleles↗
PubMed2004

Characterization of proteins secreted during maize microspore culture: arabinogalactan proteins (AGPs) stimulate embryo development.

To study molecules secreted from cultured plant cells that promote development, maize microspores were transferred into culture and the conditioned media were collected over time and analysed. Electrophoresis indicated that both non-glycosylated and glycosylated proteins including arabinogalactan proteins (AGPs) appeared in the medium and their concentration increased during the time of culture. The development of embryos was correlated with the presence of specific extracellular proteins, using an experimental system based on a tunicamycin inhibition test. In addition, a precise protein analysis was conducted using MALDI-TOF and ESI-MS-MS techniques. These approaches have allowed the identification of 5 other types of proteins: a cell wall invertase, two thaumatin isoforms, one 1-3 beta-glucanase and two chitinase isoforms. Altogether these experiments and results open ways for research aimed at understanding which molecules stimulate embryo formation. Moreover, AGPs may be used to stimulate the development of microspores (pollen embryogenesis) prepared from non-responsive genotypes.

Culture Media, Conditioned↗
PubMed2003

A DNA-damage-induced cell cycle checkpoint in Arabidopsis.

Although it is well established that plant seeds treated with high doses of gamma radiation arrest development as seedlings, the cause of this arrest is unknown. The uvh1 mutant of Arabidopsis is defective in a homolog of the human repair endonuclease XPF, and uvh1 mutants are sensitive to both the toxic effects of UV and the cytostatic effects of gamma radiation. Here we find that gamma irradiation of uvh1 plants specifically triggers a G(2)-phase cell cycle arrest. Mutants, termed suppressor of gamma (sog), that suppress this radiation-induced arrest and proceed through the cell cycle unimpeded were recovered in the uvh1 background; the resulting irradiated plants are genetically unstable. The sog mutations fall into two complementation groups. They are second-site suppressors of the uvh1 mutant's sensitivity to gamma radiation but do not affect the susceptibility of the plant to UV radiation. In addition to rendering the plants resistant to the growth inhibitory effects of gamma radiation, the sog1 mutation affects the proper development of the pollen tetrad, suggesting that SOG1 might also play a role in the regulation of cell cycle progression during meiosis.

Arabidopsis↗
PubMed2002

Determining critical pre- and post-anthesis periods and physiological processes in Lycopersicon esculentum Mill. exposed to moderately elevated temperatures.

To determine the thermosensitive periods and physiological processes in tomato flowers exposed to moderately elevated temperatures, tomato plants (Lycopersicon esculentum Mill., cv. NC 8288) were grown at 28/22 degrees C or 32/26 degrees C day/night temperature regimes and then transferred to the opposite regime for 0-15 d before or 0-24 h after anthesis. For plants initially grown at 28/22 degrees C, moderate temperature stress before anthesis decreased the percentage of fruit set per plant, but did not clarify the thermosensitive period. The same level of stress did not significantly reduce fruit set when applied immediately after anthesis. For plants initially grown at 32/26 degrees C, fruit set was completely prevented unless a relief period of more than 5 d was provided before anthesis. The same level of stress relief for 3-24 h after anthesis also increased fruit set. Plants were most sensitive to 32/26 degrees C temperatures 7-15 d before anthesis. Microscopic investigation of anthers in plants grown continuously at high temperature indicated disruption of development in the pollen, endothecium, epidermis, and stomium. This disruption was reduced, but still observable in plants relieved from high temperature for 10 d before anthesis.

Adaptation, Physiological↗
PubMed1998

Effects of topical budesonide and levocabastine on nasal symptoms and plasma exudation responses in seasonal allergic rhinitis.

This study compares the effects of two topical nasal treatments for allergic rhinitis, budesonide and levocabastine, on symptom development during seasonal pollen exposure. Additionally, the protective effects of drug treatments on allergen-challenge-induced responses (symptoms and microvascular exudation of plasma) are examined late into the pollen season. Forty-four patients with seasonal allergic rhinitis to birch pollen participated in this single-blind, randomized, and placebo-controlled study. Topical nasal treatment with either levocabastine (200 microg b.i.d.; n = 16), budesonide (200 microg b.i.d.; n = 16), or placebo (n = 12) was instituted before the start of the pollen season and continued for 5 weeks until the end of the birch pollen season. The participants kept diaries for scores of nasal and ocular symptoms. Nasal allergen challenges with increasing doses of a birch pollen extract (10[2], 10[3], and 10[4] SQ-U) were carried out both before, when patients were asymptomatic and without treatment, and late into the pollen season. A nasal lavage followed each challenge, and the lavage fluid levels of albumin were measured as an index of the acute inflammatory response of the allergic mucosa. The birch pollen season was rather mild, producing only small increases in nasal symptoms. Budesonide treatment reduced the total nasal symptoms compared to placebo (P<0.01) and to levocabastine (P<0.05), while levocabastine treatment did not differ significantly from placebo. Ocular symptoms and use of rescue medication did not differ between placebo and the active treatments. At the end of the pollen season, both treatments reduced allergen-challenge-induced nasal symptoms compared to placebo (P<0.01). Only budesonide reduced allergen-challenge-induced increments of albumin levels in postchallenge nasal lavage fluids (P<0.05, in comparison with placebo). The results suggest that budesonide reduces both seasonal and allergen-challenge-induced nasal symptoms, while levocabastine is effective against allergen-challenge-induced symptoms also during the season. In addition, the topical steroid treatment, but not the antihistamine, inhibits the inflammatory exudation evoked by allergen challenge in patients with active seasonal disease.

Administration, Intranasal↗
PubMed2025

Patterns of Genomic Divergence and Introgression in Two Primulina Hybrid Zones.

Hybrid zones have long been promoted as natural laboratories for understanding the mechanisms of speciation. Multiple or replicated hybrid zones are particularly informative, as they allow for assessing the consistency of genomic divergence and introgression across different environmental contexts and demographic histories, thereby improving our understanding of the factors that drive or hinder speciation on a broader scale. Here, using whole-genome resequencing data, we compare the patterns of genomic divergence and introgression in two Primulina hybrid zones. We found that genomic divergence in both hybrid zones is largely shaped by neutral processes, with only a few genomic regions showing signatures of balancing or lineage-specific selection. Genomic cline analyses identified numerous SNPs that showed significantly steeper clines and biased centres than the genome-wide expectation in both hybrid zones, consistent with the existence of reproductive barriers. Within regions of restricted gene flow, we identified 21 genes shared between the two hybrid zones. Annotation of gene function revealed that several genes are involved in reproductive processes. In addition, many zone-specific outlier loci were linked to genes associated with pollen and flower development, suggesting that these barriers may contribute to reproductive isolation under localised ecological conditions. Overall, these findings suggest that while certain reproductive barriers remain consistent across independent hybrid zones, others may be contingent on local environmental contexts. Our results demonstrate that both general and zone-specific mechanisms contribute to reproductive isolation in Primulina, providing empirical evidence that some genomic barriers recur across independent hybrid zones while others arise through localised adaptation.

Lamiales↗