Showing papers on "Pollen published in 2003"
TL;DR: The results suggest that ecological factors resulting from adaptive divergence are the primary isolating barriers in this system of Mimulus lewisii and M. cardinalis, sister species of monkeyflowers.
Abstract: Evolutionists have long recognized the role of reproductive isolation in speciation, but the relative contributions of different reproductive barriers are poorly understood. We examined the nature of isolation between Mimulus lewisii and M. cardinalis, sister species of monkeyflowers. Studied reproductive barriers include: ecogeographic isolation; pollinator isolation (pollinator fidelity in a natural mixed population); pollen competition (seed set and hybrid production from experimental interspecific, intraspecific, and mixed pollinations in the greenhouse); and relative hybrid fitness (germination, survivorship, percent flowering, biomass, pollen viability, and seed mass in the greenhouse). Additionally, the rate of hybridization in nature was estimated from seed collections in a sympatric population. We found substantial reproductive barriers at multiple stages in the life history of M. lewisii and M. cardinalis. Using range maps constructed from herbarium collections, we estimated that the different ecogeographic distributions of the species result in 58.7% reproductive isolation. Mimulus lewisii and M. cardinalis are visited by different pollinators, and in a region of sympatry 97.6% of pollinator foraging bouts were specific to one species or the other. In the greenhouse, interspecific pollinations generated nearly 50% fewer seeds than intraspecific controls. Mixed pollinations of M. cardinalis flowers yielded >75% parentals even when only one-quarter of the pollen treatment consisted of M. cardinalis pollen. In contrast, both species had similar siring success on M. lewisii flowers. The observed 99.915% occurrence of parental M. lewisii and M. cardinalis in seeds collected from a sympatric population is nearly identical to that expected, based upon our field observations of pollinator behavior and our laboratory experiments of pollen competition. F1 hybrids exhibited reduced germination rates, high survivorship and reproduction, and low pollen and ovule fertility. In aggregate, the studied reproductive barriers prevent, on average, 99.87% of gene flow, with most reproductive isolation occurring prior to hybrid formation. Our results suggest that ecological factors resulting from adaptive divergence are the primary isolating barriers in this system. Additional studies of taxa at varying degrees of evolutionary divergence are needed to identify the relative importance of pre- and postzygotic isolating mechanisms in speciation.
682 citations
TL;DR: A role for gamma-amino butyric acid (GABA) in pollen tube growth and guidance is described, and wild-type tubes exhibit normal growth and Guidance in pop2 pistils, perhaps by degrading excess GABA and sharpening the gradient leading to the micropyle.
538 citations
TL;DR: Results provide support for the existence of a facilitative magnet species effect in the interaction between certain nectar plants and A. morio at a site in Sweden.
Abstract: It has been debated whether pollination success in nonrewarding plants that flower in association with nectar-producing plants will be diminished by competition for pollinator visits or, alternatively, enhanced through increased local abundance of pollinators (the magnet species effect). We experimentally evaluated these effects using the nonrewarding bumblebee-pollinated orchid Anacamptis morio and associated nectar-producing plants at a site in Sweden. Pollination success (estimated as pollen receipt and pollen removal) in A. morio was significantly greater for individuals translocated to patches of nectar-producing plants (Geum rivale and Allium schoenoprasum) than for individuals placed outside (∼20 m away) such patches. These results provide support for the existence of a facilitative magnet species effect in the interaction between certain nectar plants and A. morio. To determine the spatial scale of these interactions, we correlated the visitation rate to flowers of A. morio with the density of sym...
410 citations
1 Apr 2003
391 citations
TL;DR: Diagnostic dissection of the immune response to grass pollen with potential benefits for specific immunotherapy is allowed.
Abstract: Grass pollens are one of the most important airborne allergen sources worldwide. About 20 species from five subfamilies are considered to be the most frequent causes of grass pollen allergy, and the allergenic relationships among them closely follow their phylogenetic relationships. The allergic immune response to pollen of several grass species has been studied extensively over more than three decades. Eleven groups of allergens have been identified and described, in most cases from more than one species. The allergens range from 6 to 60 kD in apparent molecular weight and display a variety of physicochemical properties and structures. The most complete set of allergens has so far been isolated and cloned from Phleum pratense (timothy grass) pollen. Based on the prevalence of IgE antibody recognition among grass pollen-sensitized individuals, several allergens qualify as major, but members of two groups, groups 1 and 5, have been shown to dominate the immune response to grass pollen extract. Isoform variation has been detected in members of several of the allergen groups, which in some cases can be linked to observed genetic differences. N-linked glycosylation occurs in members of at least three groups. Carbohydrate- reactive IgE antibodies have been attributed to grass pollen sensitization and found to cross-react with glycan structures from other allergen sources, particularly vegetable foods. Another cause of extensive cross-reactivity are the group 12 allergens (profilins), which belong to a family of proteins highly conserved throughout the plant kingdom and present in all tissues. Members of eight allergen groups have been cloned and expressed as recombinant proteins capable of specific IgE binding. This development now allows diagnostic dissection of the immune response to grass pollen with potential benefits for specific immunotherapy.
372 citations
TL;DR: The free radical scavenging effectiveness of a bee pollen as measured by the DPPH method is shown to be determined by the nature and levels of the constituent floral pollens, which can be assayed via their phenolics profiles by HPLC.
Abstract: Bee-collected pollen (“bee pollen”) is promoted as a health food with a wide range of nutritional and therapeutic properties. The objective of the current study is to evaluate the contribution made through the free radical scavenging capability of bee-collected floval pollens by their flavonoid/phenolics constituents, and to determine whether this capability is affected by aging. The free radical scavenging effectiveness of a bee pollen (EC50) as measured by the DPPH method is shown to be determined by the nature and levels of the constituent floral pollens, which can be assayed via their phenolics profiles by HPLC. Each pure floral pollen has been found to possess a consistent EC50 value, irrespective of its geographic origin or date of collection, and the EC50 value is determined to a large extent (ca. 50%) by the nature and the levels of the pollen's flavonoids and phenolic acids. Non-phenolic antioxidants, possibly proteins, account for the balance of the activity. Pollen aging over 3 years is demonst...
261 citations
TL;DR: In this paper, the authors used high-resolution pollen analysis of Vir-18 core to detect the millennial-scale climatic cyclicity suggested by North Atlantic records, challenging the apparent climatic stability reflected by the relative pollen record.
241 citations
TL;DR: In this article, a high-resolution pollen record was obtained from ODP Site 1144 (water depth 2037 m), northern South China Sea for the last 103 million years according to micropaleontological and isotopic stratigraphy The pollen assemblages are characterized by high proportions of Pinus and herb pollen, and by their frequent alternations.
229 citations
TL;DR: The results strongly suggest that poor accumulation of proteins that play a role in stress tolerance may be why Arabidopsis pollen is cold sensitive.
Abstract: We have characterized the global gene expression patterns of Arabidopsis pollen using Serial Analysis of Gene Expression (SAGE). A total of 21,237 SAGE tags were sequenced and 4,211 unique tags were identified. Interestingly, the number of unique tags in pollen was low compared with the SAGE library of the leaf constructed on a similar scale. The transcript profiles of pollen reflect accurately the characteristics of pollen as a reproductive organ. Functional classification of the expressed genes reveals that those involved in cellular biogenesis such as polygalacturonase, pectate lyase, and pectin methylesterase make up more than 40% of the total transcripts. However, genes involved in energy and protein synthesis, which are prevalent in leaves, were expressed at a relatively low level. The expression level of the great majority of transcripts was unaffected by cold treatment at 0 degrees C for 72 h, whereas pollen tube growth and seed production were substantially reduced. Interestingly, many genes thought to be responsible for cold acclimation such as COR, lipid transfer protein, and beta-amylase, that are highly induced in Arabidopsis leaves, were only expressed at their normal level or weakly induced in the pollen. The expression patterns of the cold-responsive transcripts identified by SAGE were confirmed by microarray analysis. Our results strongly suggest that poor accumulation of proteins that play a role in stress tolerance may be why Arabidopsis pollen is cold sensitive.
223 citations
TL;DR: In this article, a range-wide variation of maritime pine was studied at maternally inherited and paternally-inherited markers (mitochondrial DNA and chloroplast DNA).
Abstract: Range-wide variation of maritime pine was studied at maternally inherited and paternally inherited markers (mitochondrial DNA and chloroplast DNA). While chloroplast DNA exhibits the highest diversity, phylogeographic inferences from this marker are blurred by homoplasy and extensive pollen flow. In contrast, the only three mitochondrial haplotypes found provide a clear picture of nonoverlapping areas colonized from different refugia, with no single population having a mixed composition ( G ST = 1). Comparison of the genetic structure inferred from both organelle genomes allows the investigation of differential seed and pollen dispersal, pointing to pollen, but not seed, dispersal across the Strait of Gibraltar (from Morocco into Iberia). A comparison with already available genetic information, especially that of one of the maritime pine’s most threatening insect pests, the bast scale Matsucoccus feytaudi , further completes the picture.
205 citations
TL;DR: It is concluded that boron has a regulatory role in pollen germination and pollen tube growth and may be associated with the increased content of carboxylic acid.
Abstract: To study the role of boron in pollen germination and pollen tube growth of Picea meyeri Rehd. et Wils., pollen grains were cultured in standard medium or boron-deficient medium. Effects of boron on the localization of pectins and callose in the walls of pollen tubes were observed by laser scanning confocal microscopy after staining with aniline blue or immunolabeling with antibodies JIM5 and JIM7. Changes in the structures of pectins and phenolics were investigated by fourier transform infrared (FTIR) microspectroscopy. Pollen germination in boron-deficient medium ranged from 18 to 24%, whereas pollen germination in standard medium reached 61%. Callose accumulated in the tip-regions of pollen tubes cultured in boron-deficient medium, but not in standard medium. Immunolabeling with antibody JIM5 revealed that acidic pectin preferentially accumulated in the tip regions of pollen tubes cultured in boron-deficient medium, whereas acidic pectin was weakly distributed along the entire lengths of pollen tubes cultured in standard medium. Esterified pectin, detected by immunolabeling with antibody JIM7, showed a similar distribution pattern in pollen tubes in both the boron-deficient and standard treatments. The FTIR spectra indicated slight increases in contents of phenolics and carboxylic acids and a substantial decrease in the content of saturated esters in boron-deficient pollen tubes compared with normal pollen tubes. The FTIR spectra confirmed that boron deficiency enhanced acidic pectin accumulation in pollen tubes, which may be associated with the increased content of carboxylic acid. We conclude that boron has a regulatory role in pollen germination and pollen tube growth.
TL;DR: A high-resolution pollen record from 2 boreholes from the Changjiang (Yangtze River) delta shows a series of well-defined changes in vegetation and climate over the last 13,000 yr as discussed by the authors.
TL;DR: It is suggested that time-dependent foraging behaviors may play an important role in determining pollinator effectiveness and the significance of pollination variability for plant reproduction.
Abstract: The contribution of a pollinator toward plant fitness (i.e., its "effectiveness") can determine its importance for the plant's evolutionary ecology. We compared pollinators in a population of Asclepias incarnata (Apocynaceae) for several components of pollinator effectiveness over two flowering seasons to evaluate their importance to plant reproduction. Insects of the order Hymenoptera predominate in A. incarnata pollination, but there appears to be no specialization for pollination within this order. Pollinators varied significantly in nearly every component of effectiveness that we measured, including pollen load, removal and deposition of pollen, pollination efficiency (deposition/removal), flower-handling time, and potential for geitonogamy (fractional pollen deposition). The visitation rate of pollinators also varied significantly between years and through time within years. Pollination success and percentage fruit-set of unmanipulated plants in the population also varied significantly between years, and pollination success varied among sample times within years. Most components of effectiveness were weakly correlated, suggesting that the contributions of visitor species toward pollination varied among effectiveness components. Mean flower-handling time, however, was strongly correlated with several components, including pollen removal and deposition, pollination efficiency, and fractional pollen deposition. These findings highlight the significance of pollination variability for plant reproduction and suggest that time-dependent foraging behaviors may play an important role in determining pollinator effectiveness.
TL;DR: It is reported that PLD and PA have a role in the process of polarised plant cell expansion as represented by pollen tube growth.
Abstract: Phospholipase D (PLD) and its product phosphatidic acid (PA) are involved in a number of signalling pathways regulating cell proliferation, membrane vesicle trafficking and defence responses in eukaryotic cells. Here we report that PLD and PA have a role in the process of polarised plant cell expansion as represented by pollen tube growth. Both phosphatidylinositol-4,5-bisphosphate-dependent and independent PLD activities were identified in pollen tube extracts, and activity levels during pollen tube germination and growth were measured. PLD-mediated PA production in vivo can be blocked by primary alcohols, which serve as a substrate for the transphosphatidylation reaction. Both pollen germination and tube growth are stopped in the presence 0.5% 1-butanol, whereas secondary and tertiary isomers do not show any effect. This inhibition could be overcome by addition of exogenous PA-containing liposomes. In the absence of n-butanol, addition of a micromolar concentration of PA specifically stimulates pollen germination and tube elongation. Furthermore, a recently established link between PLD and microtubule dynamics was supported by taxol-mediated partial rescue of the 1-butanol-inhibited pollen tubes. The potential signalling role for PLD-derived PA in plant cell expansion is discussed.
TL;DR: In this paper, the authors investigated the contribution of seed and pollen dispersal to total gene flow by analyzing the pattern of decrease in kinship coefficients among pairs of individuals with geographical distance and comparing it with simulation results.
Abstract: Spatial genetic structure was analysed with five highly polymorphic microsatellite loci in a Romanian population of common ash ( Fraxinus excelsior L.), a wind-pollinated and wind-dispersed tree species occurring in mixed deciduous forests over almost all of Europe. Contributions of seed and pollen dispersal to total gene flow were investigated by analysing the pattern of decrease in kinship coefficients among pairs of individuals with geographical distance and comparing it with simulation results. Plots of kinship against the logarithm of distance were decomposed into a slope and a shape component. Simulations showed that the slope is informative about the global level of gene flow, in agreement with theoretical expectations, whereas the shape component was correlated with the relative importance of seed vs. pollen dispersal. Hence, our results indicate that insights into the relative contributions of seed and pollen dispersal to overall gene flow can be gained from details of the pattern of spatial genetic structure at biparentally inherited loci. In common ash, the slope provided an estimate of total gene dispersal in terms of Wright’s neighbourhood size of Nb = 519 individuals. No precise estimate of seed vs. pollen flow could be obtained from the shape because of the stochasticity inherent to the data, but the parameter combinations that best fitted the data indicated restricted seed flow, σ s ≤ ≤ ≤ 14 m, and moderate pollen flow, 70 m ≤ ≤ ≤ σ p ≤ ≤ ≤ 140 m.
TL;DR: Pollen-based climate reconstructions over the Late Glacial-early Holocene boundary have indicated that pollen-stratigraphical changes have been rapid with no evidence for response lags, so it is difficult to assess whether the amplitude of reconstructed climate change reflects real climate change.
Abstract: During the last decade Quaternary pollen analysis has developed towards improved pollen-taxonomical precision, automated pollen identification and more rigorous definition of pollen assemblage zones. There have been significant efforts to model the spatial representation of pollen records in lake sediments which is important for more precise interpretation of the pollen records in terms of past vegetation patterns. We review the difficulties in matching modelled post-glacial plant migration patterns with pollen-based palaeorecords and discuss the potential of DNA analysis of pollen to investigate the ancestry and past migration pathways of the plants. In population ecology there has been an acceleration of the widely advocated conceptual advance of pollen-analytical research from vaguely defined ‘environmental reconstructions’ towards investigating more precisely defined ecological problems aligned with the current ecological theories. Examples of such research have included an increasing number of invest...
TL;DR: The results show that RAFTIN is essential for the late phase of pollen development in cereals, and is targeted to microspore exine.
Abstract: Pollen fecundity is crucial to crop productivity and also to biodiversity in general. Pollen development is supported by the tapetum, a metabolically active sporophytic nurse layer that devotes itself to this process. The tapetum in cereals and a vast majority of other plants is of the nonamoeboid type. Unable to reach out to microspores, it secretes nutrients into the anther locule where the microspores reside and develop. Orbicules (Ubisch bodies), studied in various plants since their discovery ≈140 years ago, are a hallmark of the secretory tapetum. Their significance to tapetal or pollen development has not been established. We have identified in wheat and rice an anther-specific single-copy gene (per haploid genome equivalent) whose suppression in rice by RNA interference nearly eliminated the seed set. The flowers in the transgenics were normal for female functions, but the pollen collapsed and became less viable. Further characterization of the gene product, named RAFTIN, in wheat has shown that it is present in pro-orbicule bodies and it is accumulated in Ubisch bodies. Furthermore, it is targeted to microspore exine. Although the carboxyl portion of RAFTINs shares short, dispersed amino acid sequences (BURP domain) in common with a variety of proteins of disparate biological contexts, the occurrence RAFTIN per se is limited to cereals; neither the Arabidopsis genome nor the vast collection of ESTs suggests any obvious dicot homologs. Furthermore, our results show that RAFTIN is essential for the late phase of pollen development in cereals.
TL;DR: It is indicated that pollen do not only induce allergy and thus have a much broader impact on human health, and this review is an attempt to favour this holistic view of pollen and their impact onhuman health.
Abstract: The transfer of pollen from floral anther to recipient stigma is the critical reproductive event among higher plants--this is the botanical view of pollen. Proteins and glycoproteins from pollen can function as allergens, environmental molecules interacting with the human immune system to elicit an allergic response in susceptible individuals--this is how allergists and immunologists see pollen grains. Between 10 and 25% of the population now have symptoms of hay fever or allergic asthma and the incidence has more than doubled in the past three decades while the reason(s) for this increment are only hypothetical, but there is a multitude of them. Despite our natural focus on this impact of pollen on human health, pollen have to be considered in a larger context. First of all, to evaluate the bioavailability of allergens from pollen, we have to understand their function and their influence factors. Furthermore, pollen grains are not only releasing proteins eliciting specific immune responses, but they also liberate bioactive lipid mediators and this much more rapidly. And last but not least, recent observations indicate, that pollen do not only induce allergy and thus have a much broader impact on human health. This review is an attempt to favour this holistic view of pollen and their impact on human health.
TL;DR: A direct positive link between pollinator visitation rate and pollen receipt is suggested across naturally varying floral morphology in Ipomopsis aggregata, a hummingbird-pollinated plant.
Abstract: The majority of flowering plants require animals for pollination, a critical ecosystem service in natural and agricultural systems. However, quantifying useful estimates of pollinator visitation rates can be nearly impossible when pollinator visitation is infrequent. We examined the utility of an indirect measure of pollinator visitation, namely pollen receipt by flowers, using the hummingbirdpollinated plant, Ipomopsis aggregata (Polemoniaceae). Our a priori hypothesis was that increased pollinator visitation should result in increased pollen receipt by stigmas. However, the relationship between pollinator visitation rate and pollen receipt may be misleading if pollen receipt is a function of both the number of pollinator visits and variation in pollinator efficiency at depositing pollen, especially in the context of variable floral morphology. Therefore, we measured floral and plant characters known to be important to pollinator visitation and/or pollen receipt in I. aggregata (corolla length and width and plant height) and used path analysis to dissect and compare the effect of pollinator visitation rate vs. pollinator efficiency on pollen receipt. Of the characters we measured, pollinator visitation rate (number of times plants were visited multiplied by the mean percentage of flowers probed per visit) had the strongest direct positive effect on pollen receipt, explaining 36% of the variation in pollen receipt. Plant height had a direct positive effect on pollinator visitation rate and an indirect positive effect on pollen receipt. Despite the supposition that floral characters would directly affect pollen receipt as a result of changes in pollinator efficiency, corolla length and width only weakly affected pollen receipt. These results suggest a direct positive link between pollinator visitation rate and pollen receipt across naturally varying floral morphology in I. aggregata. Understanding the relationship between pollinator visitation rate and pollen receipt may be of critical importance in systems where pollinator visitation is difficult to quantify.
TL;DR: The male-specific double KO mutation is fully penetrant and shows that apyrases play a crucial role in pollen germination.
Abstract: In Arabidopsis, we previously identified two highly similar apyrases, AtAPY1 and AtAPY2. Here, T-DNA knockout (KO) mutations of each gene were isolated in a reverse genetic approach. The single KO mutants lacked a discernible phenotype. The double KO mutants, however, exhibited a complete inhibition of pollen germination, and this correlated with positive β-glucuronidase staining in the pollen of apyrase promoter:β-glucuronidase fusion transgenic lines. The vast majority of the pollen grains of these mutants were identical to wild type in size, shape, and nuclear state and were viable as assayed by metabolic activity and plasma membrane integrity. Complementation with either AtAPY1 or AtAPY2 cDNA rescued pollen germination, confirming that the phenotype was apyrase specific. Despite the redundancy of the two apyrases in rescue potential, transmission analyses suggested a greater role for AtAPY2 in male gamete success. The effect of mutant apyrase on the transmission through the female gametophyte was only marginal, and embryo development appeared normal in the absence of apyrases. The male-specific double KO mutation is fully penetrant and shows that apyrases play a crucial role in pollen germination.
TL;DR: Molecular studies of SSI are now being carried out on Ipomoea trifida and Senecio squalidus and are providing important preliminary data suggesting that SSI in these two families does not share the same molecular mechanism as that of the Brassicaceae.
Abstract: Flowering plants have evolved a multitude of mechanisms to avoid self-fertilization and promote outbreeding. Self-incompatibility (SI) is by far the most common of these, and is found in ca. 60% of flowering plants. SI is a genetically controlled pollen-pistil recognition system that provides a barrier to fertilization by self and self-related pollen in hermaphrodite (usually co-sexual) flowering plants. Two genetically distinct forms of SI can be recognized: gametophytic SI (GSI) and sporophytic SI (SSI), distinguished by how the incompatibility phenotype of the pollen is determined. GSI appears to be the most common mode of SI and can operate through at least three different mechanisms, two of which have been characterized extensively at a molecular level in the Solanaceae and Papaveraceae. Because molecular studies of SSI have been largely confined to species from the Brassicaceae, predominantly Brassica species, it is not yet known whether SSI, like GSI, can operate through different molecular mechanisms. Molecular studies of SSI are now being carried out on Ipomoea trifida (Convolvulaceae) and Senecio squalidus (Asteraceae) and are providing important preliminary data suggesting that SSI in these two families does not share the same molecular mechanism as that of the Brassicaceae. Here, what is currently known about the molecular regulation of SSI in the Brassicaceae is briefly reviewed, and the emerging data on SSI in I. trifida, and more especially in S. squalidus, are discussed.
TL;DR: The existence of long-term trends in the annual totals of daily airborne pollenconcentrations of five common and/or allergenic wind pollinating taxa was evaluated at fivepollen-monitoring stations in western Europe:Delmenhorst (D), Helmond (NL), Brussels (B),Leiden (NL) and Derby (UK).
Abstract: The existence of long-term (20–33 years) trendsin the annual totals of daily airborne pollenconcentrations of five common and/or allergenicwind pollinating taxa was evaluated at fivepollen-monitoring stations in western Europe:Delmenhorst (D), Helmond (NL), Brussels (B),Leiden (NL), and Derby (UK). At all stations,identical or comparable volumetric traps wereused to sample pollen from the air. For grasspollen no increasing or decreasing trends werefound at any station. Trends for birch pollenand oak pollen are increasing, but notsignificant at the stations with the higherannual totals (Delmenhorst and Helmond),probably due to strong year-to-yearfluctuations. At all five stations significantincreasing trends for stinging nettle pollenwere observed. Trends for mugwort pollen aresignificant at all stations, but in differentdirections. Longer periods of observations areneeded to arrive to more definitive conclusionsabout trends in airborne pollenconcentrations.
TL;DR: Pollen from wind-pollinated trees has traditionally been assumed to be abundant and to travel long distances, resulting in extensive gene flow, but short-distance dispersal of limited pollen might be common and play an important role in causing the highly variable seed production frequently observed in such species.
Abstract: Pollen from wind-pollinated trees has traditionally been assumed to be abundant and to travel long distances, resulting in extensive gene flow However, recent empirical work by Knapp et al , genetic analysis by Sork et al , and theoretical models by Satake and Iwasa conclude that short-distance dispersal of limited pollen might be common and play an important role in causing the highly variable seed production (masting) frequently observed in such species Pollen movement might be sufficiently restricted that increased fragmentation could ultimately bring about reproductive failure in some species
TL;DR: In this paper, the distribution of aeolian pollen in marine sediments is used to reconstruct pathways of terrigenous input to the oceans and provide a record of vegetation change on adjacent continents.
TL;DR: Multiple charge‐isoforms of vacuolar acid invertase, fructokinase, β‐expansin and profilin were identified, suggesting that during the process of pollen development some kind of post‐translational modification of these proteins occurs.
Abstract: We used proteomic analysis to investigate the changing patterns of protein synthesis during pollen development in anthers from rice plants grown under strictly controlled growth conditions. Cytological analysis and external growth measurements such as anther length, auricle distances and days before flowering were used to determine pollen developmental stages. This allowed the collection of synchronous anther materials representing six discrete pollen developmental stages. Proteins were extracted from the anther samples and separated by two-dimensional gel electrophoresis to produce proteome maps. The anther proteome maps of different developmental stages were compared and 150 protein spots, which were changed consistently during development, were analysed by matrix-assisted laser desorption/ionization-time of flight mass spectrometry to produce peptide mass fingerprint (PMF) data. Database searches using these PMF data revealed the identities of 40 of the protein spots analyzed. These 40 proteins represent 33 unique gene products. Four protein spots that could not be identified by PMF analysis were analysed by N-terminal microsequencing. Multiple charge-isoforms of vacuolar acid invertase, fructokinase, beta-expansin and profilin were identified. These proteins are closely associated with sugar metabolism, cell elongation and cell expansion, all of which are cell activities that are essential to pollen germination. The existence of multiple isoforms of the same proteins suggests that during the process of pollen development some kind of post-translational modification of these proteins occurs.
Journal Article•
TL;DR: Clinical and immunological evaluations have revealed allergenically important texa - some of them for the first time - among various pollen allergens in India.
Abstract: Allergic diseases such as bronchial asthma, allergic rhinitis and atopic dermatitis are dramatically increasing all over the world including developing countries like India. Today, more than 30 % of the population is known to suffer from one or other allergic ailment. Major causative agents implicated are pollen grains, fungal spores, dust mites, insect debris, animal epithelia, etc. Several aerobiological studies have been conducted in different parts of the country to ascertain aerial concentration and seasonality of pollen grains and fungi. Recently, an "All India Coordinated Project on Aeroallergens and Human Health" was undertaken to discover the quantitative and qualitative prevalence of aerosols at 18 different centres in the country. Predominant airborne pollen are Holoptelea, Poaceae, Asteraceae, Eucalyptus, Casuarina, Putanjiva, Cassia, Quercus, Cocos, Pinus, Cedrus, Ailanthus, Cheno/Amaranth, Cyperus, Argemone, Xanthium, Parthenium and others. Clinical and immunological evaluations have revealed allergenically important texa - some of them for the first time. Allergenically important pollen are Prosopis juliflora, Ricinus communis, Morus, Mallotus, Alnus, Querecus, Cedrus, Argemone, Amaranthus, Chenopodium, Holoptelea, Brassica, Cocos, Cannabis, Parthenium, Cassia and grasses. Further cross-reactivity of the IgE antibodies is a common phenomenon among various pollen allergens. Ricinus communis pollen from commonly growing weeds in India, cross-reacts with latex (Hevea brasiliensis), Mercurialis annua and also with seeds of Ricinus communis - all belonging to family Euphorbiaceae. Areca catechu cross-reacts with other members of Arecaceae such as Phoenix sylvestris, Cocos nucifera and Borassus flabelifer. Several reports on pollen and fruit syndrome have been analyzed. Experiments conducted by us revealed that pollutants (NO(2) and SO(2)) not only affect pollen morphology but also changes their allergenic potency. Immunotherapy with recombinant proteins having similar epitopes from different allergens have been advocated, besides allergen avoidance.
TL;DR: The relationship between floral density and plant reproductive success is addressed using two experimental approaches: a pollen supplementation experiment in 12 populations of Trillium grandiflorum that naturally varied in floral density, and a transplant experiment in which floral density was manipulated in plots at four experimental sites.
Abstract: Decreases in floral density can disrupt mutualistic interactions between plants and their pollinators, and decrease reproductive success. I addressed the relationship between floral density and plant reproductive success using two experimental approaches: a pollen supplementation experiment in 12 populations of Trillium grandiflorum that naturally varied in floral density, and a transplant experiment in which floral density was manipulated in plots at four experimental sites. In the pollen supplementation experiments, the degree of pollen limitation, in terms of fruit set and seed set, decreased with floral density. Further, in the experimental sites, plant reproductive success increased asymptotically with floral density. These results demonstrate the value of simultaneously conducting experiments in both experimental sites and natural populations to understand how population density influences plant reproductive success. Factors that reduce the density of this perennial herb, such as habitat fragmentation and herbivory by white-tailed deer (Odocoileus virginianus), should be expected to limit its reproduction.
TL;DR: The study demonstrates the negative effect that habitat disruption has on bat pollinators in tropical dry forest ecosystems and documents the negative consequences for the plants they pollinate.
Abstract: In the tropical dry forest of the central Pacific coast of Mexico the pollination and reproductive success of the bombacaceous tree Ceiba grandiflora was nega- tively affected by habitat disruption. Two of the three bat species that function as effective pollinators for this species (Glossophaga soricina and Musonycteris har- risoni) visited flowers found in trees in disturbed habitats significantly less than trees found in undisturbed habitats. A similar pattern was observed for the effective bat pollinator, Leptonycteris curasoae; however the differ- ence was not significant. The three nectarivorous bats that functioned as effective pollinators of C. grandiflora also visited flowers to exclusively feed on pollen by biting or pulling off an anther (see Fig. S1 of Electronic Supple- mentary Material). The number of pollen grains deposited on stigmas from flowers in undisturbed areas was significantly greater than from flowers in disturbed habitats. The greater visitation rate and the greater number of pollen grains deposited on flowers from trees in undisturbed forest resulted in a significantly greater fruit set for trees in these areas. Our study demonstrates the negative effect that habitat disruption has on bat pollinators in tropical dry forest ecosystems and docu- ments the negative consequences for the plants they pollinate. Electronic Supplementary Material Supplementary material is available for this article if you access the article at http://dx.doi.org/10.1007/s00442-003-1234-3. A link in the frame on the left on that page takes you directly to the supplementary material.
TL;DR: This data indicates that the number of IgE‐mediated allergies and the disease‐eliciting allergens in tropical Africa are higher than in other regions of the world studied.
Abstract: Summary
Background Almost no information is available regarding the prevalence of IgE-mediated allergies and the disease-eliciting allergens in tropical Africa.
Objective To study IgE-mediated allergies and the allergen profile in allergic patients from Zimbabwe.
Methods The frequency of sensitization to common environmental allergen sources was determined by skin prick testing in 650 allergic patients from Zimbabwe. Fifty representative sera were analysed for IgE reactivity to 20 respiratory and 20 food allergen extracts by multiallergen extract testing. The IgE reactivity profiles to recombinant pollen and mite allergens were compared between grass pollen- and mite-sensitized patients from Zimbabwe and central Europe. Sera from grass pollen-allergic patients were also analysed for IgE reactivity to nitrocellulose-blotted natural timothy grass and Bermuda grass pollen allergens.
Results IgE-mediated allergies were found to be common in Zimbabwe. Similar to the situation in central Europe, mites and grass pollens represented the most prevalent allergen sources. However, the IgE reactivity profiles determined with single recombinant pollen and mite allergens revealed interesting differences between the European and African patients, which most likely reflect the local allergen exposure.
Conclusions The striking differences regarding sensitization to grass pollen and mite allergens between African and European patients revealed by recombinant allergen-based testing emphasize the need for component-resolved allergy testing to optimize allergy prevention and therapy in different populations.
TL;DR: The positive effect of a supplemental food source on thrips does not necessarily mean it is unsuitable for the preventative introduction of thrips predators, because the supplemental food can also affect the population dynamics of the predator and the predator–prey interaction and, hence, the outcome of biological control.
Abstract: The development time, fecundity, longevity, and resultant intrinsic growth rate of the western flower thrips Frankliniella occidentalis (Pergande) [Thysanoptera: Thripidae] encaged on a cucumber leaf were compared among seven types of food supplied: six pollen species and a mixture of milk powder and yeast The rationale was to find a food source that offers the least benefit for thrips and could therefore be considered as a food source for the preventative introduction of thrips predators With the exception of the mixture of milk powder and yeast, all the food sources tested offered a nutritional benefit for the thrips The addition of pollen increased fecundity and reduced development time, mainly during the larval stage Betula pubescens and Corylus avellana pollen also increased adult longevity The nutritional benefit of Pinus sylvestris pollen was greater than that of the other five pollen species, as manifested by its significantly greater positive effect on fecundity The other pollen species could not be ranked in terms of nutritional benefit to F occidentalis The negative effect of the milk powder plus yeast mix on the life-table parameters of F occidentalis probably only occurs in an encaged situation where thrips cannot escape from the unfavorable environment The crude estimate of the intrinsic growth rate of F occidentalis increased from 0163 on the plain cucumber leaf to 0240 when P sylvestris pollen was added to the leaf The differences in intrinsic growth rate mainly reflect the differences in fecundity among the food sources Thus, the peak oviposition rate may be used as a measure of the nutritional benefit F occidentalis can obtain by feeding on supplemental food sources The positive effect of a supplemental food source on thrips does not necessarily mean it is unsuitable for the preventative introduction of thrips predators, because the supplemental food can also affect the population dynamics of the predator and the predator-prey interaction and, hence, the outcome of biological control