Regulation of ion transport across the pollen tube plasmalemma by hydrogen peroxide

The polar growth of the pollen tube is a key stage in the life cycle of seed plants, which is critical for successful sexual reproduction. One of the most important components of this process is ion transport across the cell membrane coordinated in time and space. Different classes of signal molecules, including reactive oxygen species, as has been found recently, participate in regulation of ion transmembrane transport. In this study, based on the model system of subprotoplasts isolated from pollen tubes, we showed that hydrogen peroxide can regulate two targets located on the plasma membrane: nifedipine-sensitive Ca²⁺ channels and ion transport, both of which control the membrane potential. The interaction of hydrogen peroxide with these targets resulted in an increase in an intracellular Ca²⁺ concentration and hyperpolarization of the plasma membrane. Faster regeneration of the cell wall was a consequence of elevation of the Ca²⁺ intracellular concentration.     

Quantitative dynamics of Ambrosia pollen grains in Bulgaria

The aerobiological study of the Ambrosia pollen in Sofia, Bulgaria began in 1991. The quantitative dynamics of Ambrosia pollen grains during the last seven years was determined by Chebishev's method of parabolic interpolation with orthogonal polynoms. Thesensitization to ragweed pollen was investigated in random groups of patients with clinical manifestation of hay fever.This investigation proves the previouslyobserved tendency of an increase in thespreading of Ambrosia pollen in Bulgaria.     

Hydrogen peroxide formation and iron ion oxidoreduction linked to NADH oxidation in radish plasmalemma vesicles

Previously, we showed the presence in radish (Raphanus sativus L.) plasmalemma vesicles of an NAD(P)H oxidase, active at pH 4.5-5.0, which elicits the formation of anion superoxide (Vianello and Macrí (1989) Biochim. Biophys. Acta 980, 202-208). In this work, we studied the role of hydrogen peroxide and iron ions upon this oxidase activity. NADH oxidation was stimulated by ferrous ions and, to a lesser extent, by ferric ions. Salicylate and benzoate, two known hydroxyl radical scavengers, inhibited both basal and iron-stimulated NADH oxidase activity. The iron chelators EDTA (ethylenediaminetetraacetic acid) and DFA (deferoxamine melysate) at high concentrations (2 mM) inhibited the NADH oxidation, whereas they were ineffective at lower concentrations (80 microM); the subsequent addition of ferrous ions caused a rapid and limited increase of oxygen consumption which later ceased. Hydrogen peroxide was not detected during NADH oxidation but, in the presence of salicylate, its formation was found in significant amounts. NADH oxidase activity was also associated to a Fe2+ oxidation which was only partially inhibited by salicylate. Ferrous ion oxidation was partially inhibited by catalase and prevented by superoxide dismutase, while ferric ion reduction was abolished by catalase and unaffected by superoxide dismutase. These results show that during NADH oxidation iron ions undergo oxidoreduction and that hydrogen peroxide is produced and rapidly consumed. As previously suggested, this oxidation appears linked to the univalent oxidoreduction of iron ions by a reduced flavoprotein of radish plasmalemma which is then converted to a radical form. The latter, reacting with oxygen generates the superoxide anion which dismutases to H2O2. Hydrogen peroxide, through a Fenton's reaction, may react with Fe2+ to produce hydroxyl radicals, or with Fe3+ to generate the superoxide anion.     

Cytoplasmic cisterns structurally linked with the plasmalemma in the hepatocytes of mice of different lines]

Structures of the granular endoplasmic reticulum and narrow canals formed by smooth membranes were found in the cell membrane of male mice belonging to strains CBA, C57BL and L-NZB/BLN. The canals were seen connected with plasma membranes. Under the conditions of CC1(4) poisoning of CBA and C57BL mice, these canals were transformed to gigantic cytoplasmic vacuoles. Their cavities were communicated with the extracellular space. It still remains unclear if the membranes of these canals belong to the cytoplasmic membrane or to the endoplasmic reticulum.     

Storage of pollen grains of Crotalaria retusa in oils

Summary Attempts were made to store pollen grains of Crotalaria retusa L. in a mineral oil (paraffin oil) and two vegetable oils (soybean oil and olive oil). Under laboratory conditions pollen grains not stored in oil lost in vitro germinability within 15–30 days, while those stored in oils maintained some degree of germinability even after 60 days. Pollen samples stored in oils at –20° C did not show any decline in germinability or pollen tube vigour even after 6 months of storage. The results amply demonstrate the feasibility of using oils for short- and long-term pollen storage.     

An approach to the knowledge of pollen and allergen diversity through lipid transfer protein localisation in taxonomically distant pollen grains

The aim of the present study is to localise non‐specific lipid transfer proteins (nsLTPs), obtained from Rosaceae (Prunus persica (L.) Batsch) in pollen grains of taxonomically distant plants, such as Iridaceae (Aristea latifolia G.J. Lewis), Platanaceae (Platanus acerifolia (Aiton) Willd.) and Urticaceae (Parietaria judaica L.), in order to compare pollen and nsLTP diversity. A combination of transmission electron microscopy, immunocytochemical techniques, and rabbit specific antiserum against peach nsLTPs (Pru p 3) were used. Abundant labelling to Pru p 3‐like proteins was observed in the cytoplasm, walls and pollenkitt of A. latifolia pollen grains. The presence of nsLTPs associated with the pollenkitt proves that it takes part in the defence mechanism of pollen grains. The labelling was less intense in the cytoplasm and walls of P. acerifolia. Immuno‐stained gold particles were associated with the vacuoles, lipid inclusions, endoplasmic reticulum and Golgi complex. No significant labelling was found in the P. judaica pollen grains incubated with anti‐Pru p 3 polyclonal antibodies. These results indicate important variations in the nsLTPs of different pollen species. Consequently, no taxonomic relationship between pollen grains and nsLTPs could be established.     

Electron tomography of structures in the wall of hazel pollen grains

The three-dimensional structure of channels and bacula cavities in the wall of hazel pollen grains was investigated by automated electron tomography in order to explore their role in the release of allergen proteins from the pollen grains. 3D reconstructions of 100–150 nm thick resin-embedded sections, stabilized by thin platinum–carbon coating, revealed that the channels aimed directly towards the surface of the grain and that the bacula cavities were randomly sized and merged into larger ensembles. The number and the dimensions of the ensembles were quantitatively determined by neighboring voxel analysis on thresholded reconstructed volumes. To simulate the allergen release, allergen proteins were approximated by a hard sphere model of a diameter corresponding to the largest dimension of the known 3D structure of the major birch allergen, Bet v 1, whose amino acid sequence is highly similar to the amino acid sequence of the major hazel allergen, Cor a 1. The analysis of positions where the hard sphere fits into the resolved channels and bacula cavity structures revealed that unbound allergens could freely traverse through the channels and that the bacula cavities support the path of the allergens towards the surface of the grain.     

Fine structure of sperm cells in pollen grains ofBeta

Summary The structure of sperm cells in mature trinucleate pollen grains ofBeta vulgaris L. was studied with the electron microscope. The ellipsoidal sperm cell nuclei and cytoplasm are products of mitosis and cytokinesis of the ellipsoidal generative cell. Each sperm cell is separated from the vegetative cytoplasm by two contiguous membranes which enclose its cytoplasm and nucleus. Microtubules present in the sperm cell cytoplasm may be responsible for sperm cell motility.Approved as Journal paper Nr. 846, Utah Agricultural Experiment Station, Logan, Utah.     

Cloned fragment of diphtheria toxin linked to T cell-specific antibody identifies regions of B chain active in cell entry

The role of discrete domains of diphtheria toxin (DT) B chain in cytosol entry and cytotoxicity was investigated by linking a monoclonal antibody recognizing the human T cell-specific antigen T3 (UCHT1) to diphtheria toxin (UCHT1-DT), DT A subunit (UCHT1-DTA), or to a genetically engineered form of DT (UCHT1-MspSA) lacking the C-terminal 17-kDa portion of the B subunit. The N-terminal 21-kDa region of DT B chain increased toxicity of UCHT1-DTA 100-fold (UCHT1-MspSA) while addition of the C-terminal 17-kDa region (UCHT1-DT) increased toxicity 100-fold more. The cytotoxicity was dependent upon antibody binding as demonstrated by blocking toxicity with excess UCHT1. The differences in toxicity between these reagents were not due to differences in ADP-ribosylation activity of DT A chain, binding activity of the antibody moiety, extent of DT nicking, or the cross-linking method, so we conclude that the large differences in toxicity were due to the presence of different B chain domains. The large increase in toxicity by the C-terminal region of DT B did not appear to be caused by DT receptor binding. The lysosomotropic agent NH4Cl blocked the cytotoxic effect of DT, UCHT1-DT, and UCHT1-MspSA but not UCHT1-DTA.     

Prevalence of allergenic pollen grains in the aerosol of the city of Calcutta,India: a two year study

The role of pollen grains as a causative agent of respiratory allergic disorders such as asthma and allergic rhinitis is common and very well established. The aim of this study was to assess the frequencies of airborne pollen in the Calcutta metropolis and to identify the taxa which cause significant amounts of sensitization. An aeropalynological survey of the atmosphere of Calcutta was carried out from 2004 to 2006. Skin tests were performed with a panel of the most common pollen types on local patients with clinical features of pollinosis. The meteorological factors responsible for the frequency of the pollen types were analysed. The results of monthly visits to the clinic by these patients were correlated with the monthly pollen counts of three dominant and perennial pollen taxa. The dominant pollen types were Trema (19%), Poaceae (12.98%), Casuarina (5.76%), Cocos (5.7%), Azadirachta (4.65%), Peltophorum (3.71%), Cyperaceae (3.68%), Delonix (3.18%) and Areca (2.56%). Total pollen concentration seems to have a significant positive correlation with temperature and wind speed whereas there was a negative correlation with humidity. Skin tests were most frequently found to be positive with the pollen of Poaceae (49%), Azadirachta (46%), Cocos (47%), Cyperaceae (35%), Peltophorum (33%), Areca (29%), Phoenix (26%), and Borassus (23%). A positive correlation occurred between visits to the clinic and monthly pollen count of Areca, Cocos, and Poaceae. This is the first study to design a pollen calendar for Calcutta city; it will provide useful data for enabling allergologists to achieve accurate diagnosis for patients with pollen hypersensitivity.     

Viral particles in developing pollen grains of Olea europaea

Double-walled tubules containing rows of isodiametric virus particles were observed in developing pollen grains of Olea europaea L. cultivar Correggiolo. Sometimes the tubules are contained in another double-walled tubular structure or in a tubular endoplasmic reticulum cistern. The viruses are present in the cytoplasm from the microspore mother cell stage up to the microspore stage but just before the first haploid mitosis they are to be found only in the pores, inside the evaginations formed by the plasmalemma. During the last phase of pollen grain development, after the germinative pores are completed, the viruses disappear.Abbreviations ER endoplasmic reticulum     

A molecular approach to species identification of Chenopodiaceae pollen grains in surface soil

Pollen identification and classification are important not only for palynologists, but also for systematists and ecologists. Because palynological methods for the identification of pollen in surface soil until now could resolve at best to the generic level, we have developed a molecular approach to species-level identification of Chenopodiaceae pollen in surface soils. Surface soil samples were collected in the central area of Junggar Desert Basin, Xinjiang, China. Fresh leaves of 19 Chenopodiaceae species were sampled for DNA sequencing, establishing a database of internal transcribed spacer (ITS) regions of nuclear ribosomal DNA for Chenopodiaceae. Individual chenopod pollen grains in a soil sample were separated from the soil and the ITS1 region of each pollen grain was amplified using nested PCR and sequenced. By comparing the amplified ITS1 sequences to those in the Chenopodiaceous database, we identified the pollen in the soil samples to the level of species. The new method provides a technical reference for species identification of soil surface pollen for other families. This work is necessary for further efforts to interpret the relationship of surface soil pollen to vegetation characteristics. It also has significant potential for enhancing the ability to identify pollen in clinical airborne allergen or criminological studies.     

Biogenesis and function of the lipidic structures of pollen grains

 Pollen grains contain several lipidic structures, which play a key role in their development as male gametophytes. The elaborate extracellular pollen wall, the exine, is largely formed from acyl lipid and phenylpropanoid precursors, which together form the exceptionally stable biopolymer sporopollenin. An additional extracellular lipidic matrix, the pollen coat, which is particularly prominent in entomophilous plants, covers the interstices of the exine and has many important functions in pollen dispersal and pollen-stigma recognition. The sporopollenin and pollen coat precursors are both synthesised in the tapetum under the control of the sporophytic genome, but at different stages of development. Pollen grains also contain two major intracellular lipidic structures, namely storage oil bodies and an extensive membrane network. These intracellular lipids are synthesised in the vegetative cell of the pollen grain under the control of the gametophytic genome. Over the past few years there has been significant progress in elucidating the composition, biogenesis and function of these important pollen structures. The purpose of this review is to describe these recent advances within the historical context of research into pollen development. Received: 1 November 1997 / Revision accepted: 3 February 1998     

A comparative study on the allergenicity, structure, and ultrastructure of two Acacia pollen grains in guinea pigs

Acacia saligna and Acacia victoria are native to Australia brought to and grown in Southern Iran. They have since had a widespread distribution and become native in Iran. As people of the region are exposed to the pollen grains from these plants during a 5 months period, this study aimed at investigating the allergenicity of their mature pollen grains. In addition, the structural and ultrastructural as well as the total protein content of the mature pollen grains were analyzed. Pollen grains of A. saligna and A. victoria were collected from the suburbs of Ahvaz, Iran. Pollen extracts (15 % concentration) were prepared in PBS (pH 7.2), and 4- to 6-week-old male guinea pigs (Hartly) were used for allergenicity tests. Skin tests showed a significant increase in flare diameter. Clinical tests also showed a significant change in the levels of eosinophils, neutrophils, and IgE. Comparative analysis of the allergenicity of A. saligna and A. victoria pollen grains revealed a higher IgE level in the latter. Comparative analysis of pollen characteristics was performed using both light and electron microscopy for sporoderm structure and ultrastructure, respectively. Twelve percent PAGE analysis of the total protein content of mature pollen grains showed a greater number of bands in A. victoria, while four bands were common in both species. In conclusion, this study demonstrates that both A. saligna and A. victoria pollen grains are allergenic, with a greater allergenicity of A. victoria pollen grains. In addition, the structural and ultrastructural as well as the total protein content of the mature pollen grains are revealed, and a potential protein allergen is proposed.     

Immunolocalization of H+-ATPases in the plasma membrane of pollen grains and pollen tubes ofLilium longiflorum

Summary A heterogeneous distribution of H⁺-ATPase was visualized in germinated pollen ofLilium longiflorum using monoclonal antibodies raised against plasma membrane H⁺-ATPase. Immunolocalization studies of protoplasts and subprotoplasts derived from pollen tubes and sectioned pollen grains and pollen tubes show that H⁺-ATPases are abundant in the plasma membrane of pollen grains but are absent or sparsely distributed in the plasma membrane of pollen tubes. This polar distribution of H⁺-ATPases is probably the basis of the endogenous current pattern measured in growing lily pollen and involved in pollen tube tip growth.Abbreviations BSA bovine serum albumine - Hepes N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid - Mes 2-(N-morpholino)-ethane sulphonic acid - PBS phosphate buffered saline - Pipes piperazine-N,N-bis(2-ethanesulfonic acid) - Tris 2-amino-2-hydroxymethyl-1,3-propandiol     

长梗苦草花粉粒的电镜观察

通过扫描电镜和透射电镜首次对沉水植物梗苦草（Vallisneria longipedunculata)的花粉粒进行了观察,其花粉粒的细胞壁非常薄,无萌发孔,但有2－3个具有较质丝的凹穴。花粉粒细胞壁的覆盖层十分不明显。具散生的颗粒;外壁内层较为厚实,但柱状结构分化不明显,整体呈海绵状;花粉内壁较厚。在花粉粒内部,有大量的单粒和复粒的淀粉粒,但未见到半复粒。     

New details on the morphology of fossil onagraceous pollen grains

Fossil onagraceous pollen grains from two Upper Miocene localities in E. Austria were investigated by LM and EM. Exine structure and sculpture as well as viscin threads suggest affinities with the extant genusCircea.