Plant-derived smoke stimulates seed germination in numerous plant species. Smoke also has a positive stimulatory effect on pollen germination and pollen tube growth. The range of plant families affected my smoke still needs to be established since the initial study was restricted to only three species from the Amaryllidaceae. The effects of smoke-water (SW) and the smoke-derived compounds, karrikinolide (KAR1 ) and trimethylbutenolide (TMB) on pollen growth characteristics were evaluated in seven different plant families. Smoke-water (1:1000 and 1:2000 v:v) combined with either Brewbaker and Kwack's (BWK) medium or sucrose and boric acid (SB) medium significantly improved pollen germination and pollen tube growth in Aloe maculata All., Kniphofia uvaria Oken, Lachenalia aloides (L.f.) Engl. var. aloides and Tulbaghia simmleri P. Beauv. Karrikinolide (10(-6) and 10(-7) m) treatment significantly improved pollen tube growth in A. maculata, K. uvaria, L. aloides and Nematanthus crassifolius (Schott) Wiehle compared to the controls. BWK or SB medium containing TMB (10(-3) m) produced significantly longer pollen tubes in A. maculata, K. uvaria and N. crassifolius. These results indicate that plant-derived smoke and the smoke-isolated compounds may stimulate pollen growth in a wide range of plant species.

• Keywords
• Karrikinolide, pollen germination, pollen tube growth, smoke-water, trimethylbutenolide,
• MeSH
• Furans pharmacology   MeSH
• 4-Butyrolactone analogs & derivatives   pharmacology   MeSH
• Smoke MeSH
• Culture Media MeSH
• Liliaceae drug effects   MeSH
• Pollen drug effects   growth & development   MeSH
• Pollen Tube drug effects   growth & development   MeSH
• Pyrans pharmacology   MeSH
• Water MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• butenolide MeSH Browser
• Furans MeSH
• 4-Butyrolactone MeSH
• karrikinolide MeSH Browser
• Smoke MeSH
• Culture Media MeSH
• Pyrans MeSH
• Water MeSH

Pollen germination as a crucial process in plant development strongly depends on the accessibility of carbon as energy source. Carbohydrates, however, function not only as a primary energy source, but also as important signaling components. In a comprehensive study, we analyzed various aspects of the impact of 32 different sugars on in vitro germination of Arabidopsis pollen comprising about 150 variations of individual sugars and combinations. Twenty-six structurally different mono-, di- and oligosaccharides, and sugar analogs were initially tested for their ability to support pollen germination. Whereas several di- and oligosaccharides supported pollen germination, hexoses such as glucose, fructose and mannose did not support and even considerably inhibited pollen germination when added to germination-supporting medium. Complementary experiments using glucose analogs with varying functional features, the hexokinase inhibitor mannoheptulose and the glucose-insensitive hexokinase-deficient Arabidopsis mutant gin2-1 suggested that mannose- and glucose-mediated inhibition of sucrose-supported pollen germination depends partially on hexokinase signaling. The results suggest that, in addition to their role as energy source, sugars act as signaling molecules differentially regulating the complex process of pollen germination depending on their structural properties. Thus, a sugar-dependent multilayer regulation of Arabidopsis pollen germination is supported, which makes this approach a valuable experimental system for future studies addressing sugar sensing and signaling.

• Keywords
• Arabidopsis thaliana, Carbohydrates, Metabolic regulation, Pollen germination, Signaling, Structure–function relationship,
• MeSH
• Arabidopsis drug effects   physiology   MeSH
• Hexoses metabolism   pharmacology   MeSH
• Germination drug effects   physiology   MeSH
• Mannose metabolism   pharmacology   MeSH
• Carbohydrate Metabolism * MeSH
• Oligosaccharides chemistry   metabolism   pharmacology   MeSH
• Pollen metabolism   physiology   MeSH
• Carbohydrates MeSH
• Sucrose metabolism   pharmacology   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Hexoses MeSH
• Mannose MeSH
• Oligosaccharides MeSH
• Carbohydrates MeSH
• Sucrose MeSH

Tobacco mature pollen has extremely desiccated cytoplasm, and is metabolically quiescent. Upon re-hydration it becomes metabolically active and that results in later emergence of rapidly growing pollen tube. These changes in cytoplasm hydration and metabolic activity are accompanied by protein phosphorylation. In this study, we subjected mature pollen, 5-min-activated pollen, and 30-min-activated pollen to TCA/acetone protein extraction, trypsin digestion and phosphopeptide enrichment by titanium dioxide. The enriched fraction was subjected to nLC-MS/MS. We identified 471 phosphopeptides that carried 432 phosphorylation sites, position of which was exactly matched by mass spectrometry. These 471 phosphopeptides were assigned to 301 phosphoproteins, because some proteins carried more phosphorylation sites. Of the 13 functional groups, the majority of proteins were put into these categories: transcription, protein synthesis, protein destination and storage, and signal transduction. Many proteins were of unknown function, reflecting the fact that male gametophyte contains many specific proteins that have not been fully functionally annotated. The quantitative data highlighted the dynamics of protein phosphorylation during pollen activation; the identified phosphopeptides were divided into seven groups based on the regulatory trends. The major group comprised mature pollen-specific phosphopeptides that were dephosphorylated during pollen activation. Several phosphopeptides representing the same phosphoprotein had different regulation, which pinpointed the complexity of protein phosphorylation and its clear functional context. Collectively, we showed the first phosphoproteomics data on activated pollen where the position of phosphorylation sites was clearly demonstrated and regulatory kinetics was resolved.

• MeSH
• Phosphoproteins chemistry   metabolism   MeSH
• Kinetics MeSH
• Proteomics methods   MeSH
• Pollen metabolism   MeSH
• Gene Expression Regulation, Plant MeSH
• Plant Proteins chemistry   metabolism   MeSH
• Nicotiana genetics   metabolism   MeSH
• Tandem Mass Spectrometry methods   MeSH
• Binding Sites MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Phosphoproteins MeSH
• Plant Proteins MeSH

Being rooted in place, plants are faced with the challenge of responding to unfavourable local conditions. One such condition, heat stress, contributes massively to crop losses globally. Heatwaves are predicted to increase, and it is of vital importance to generate crops that are tolerant to not only heat stress but also to several other abiotic stresses (e.g. drought stress, salinity stress) to ensure that global food security is protected. A better understanding of the molecular mechanisms that underlie the temperature stress response in pollen will be a significant step towards developing effective breeding strategies for high and stable production in crop plants. While most studies have focused on the vegetative phase of plant growth to understand heat stress tolerance, it is the reproductive phase that requires more attention as it is more sensitive to elevated temperatures. Every phase of reproductive development is affected by environmental challenges, including pollen and ovule development, pollen tube growth, male-female cross-talk, fertilization, and embryo development. In this review we summarize how pollen is affected by heat stress and the molecular mechanisms employed during the stress period, as revealed by classical and -omics experiments.

• Keywords
• heat stress (HS), heat stress response (HSR), multiomics, pollen development, thermotolerance,
• MeSH
• Stress, Physiological MeSH
• Pollen MeSH
• Heat-Shock Response MeSH
• Plant Breeding * MeSH
• Thermotolerance * MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH

Angiosperm mature pollen represents a quiescent stage with a desiccated cytoplasm surrounded by a tough cell wall, which is resistant to the suboptimal environmental conditions and carries the genetic information in an intact stage to the female gametophyte. Post pollination, pollen grains are rehydrated, activated, and a rapid pollen tube growth starts, which is accompanied by a notable metabolic activity, synthesis of novel proteins, and a mutual communication with female reproductive tissues. Several angiosperm species (Arabidopsis thaliana, tobacco, maize, and kiwifruit) were subjected to phosphoproteomic studies of their male gametophyte developmental stages, mostly mature pollen grains. The aim of this review is to compare the available phosphoproteomic studies and to highlight the common phosphoproteins and regulatory trends in the studied species. Moreover, the pollen phosphoproteome was compared with root hair phosphoproteome to pinpoint the common proteins taking part in their tip growth, which share the same cellular mechanisms.

• Keywords
• kinase motif, male gametophyte, phosphoproteomics, pollen tube, root hair, signal transduction,
• MeSH
• Phosphoproteins metabolism   MeSH
• Pollination * MeSH
• Proteome metabolism   MeSH
• Proteomics * MeSH
• Pollen Tube metabolism   MeSH
• Plant Proteins metabolism   MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• Phosphoproteins MeSH
• Proteome MeSH
• Plant Proteins MeSH

Pollen grains are the male gametophytes in a seed-plant life cycle. Their small, particulate nature and crucial role in plant reproduction have made them an attractive object of study using flow cytometry (FCM), with a wide range of applications existing in the literature. While methodological considerations for many of these overlap with those for other tissue types (e.g., general considerations for the measurement of nuclear DNA content), the relative complexity of pollen compared to single cells presents some unique challenges. We consider these here in the context of both the identification and isolation of pollen and its subunits, and the types of research applications. While the discussion here mostly concerns pollen, the general principles described here can be extended to apply to spores in ferns, lycophytes, and bryophytes. In addition to recommendations provided in more general studies, some recurring and notable issues related specifically to pollen and spores are highlighted.

• Keywords
• DNA content, best practices, flow cytometry, genome size, ploidy level, pollen grains,
• MeSH
• Cell Nucleus MeSH
• Ploidies MeSH
• Flow Cytometry MeSH
• Pollen * MeSH
• Spores * MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

Fertilization in angiosperms involves the germination of pollen on the stigma, followed by the extrusion of a pollen tube that elongates through the style and delivers two sperm cells to the embryo sac. Sexual selection could occur throughout this process when male gametophytes compete for fertilization. The strength of sexual selection during pollen competition should be affected by the number of genotypes deposited on the stigma. As increased self-fertilization reduces the number of mating partners, and the genetic diversity and heterozygosity of populations, it should thereby reduce the intensity of sexual selection during pollen competition. Despite the prevalence of mating system shifts, few studies have directly compared the molecular signatures of sexual selection during pollen competition in populations with different mating systems. Here we analyzed whole-genome sequences from natural populations of Arabis alpina, a species showing mating system variation across its distribution, to test whether shifts from cross- to self-fertilization result in molecular signatures consistent with sexual selection on genes involved in pollen competition. We found evidence for efficient purifying selection on genes expressed in vegetative pollen, and overall weaker selection on sperm-expressed genes. This pattern was robust when controlling for gene expression level and specificity. In agreement with the expectation that sexual selection intensifies under cross-fertilization, we found that the efficacy of purifying selection on male gametophyte-expressed genes was significantly stronger in genetically more diverse and outbred populations. Our results show that intra-sexual competition shapes the evolution of pollen-expressed genes, and that its strength fades with increasing self-fertilization rates.

• Keywords
• gametophyte, mating system, ploidy, pollen competition, sexual selection,
• MeSH
• Arabis * MeSH
• Genomics MeSH
• Sexual Selection MeSH
• Pollen genetics   MeSH
• Self-Fertilization MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

Birch and other related trees of the families Betulaceae and Fagaceae (alder, hazel, oak, hornbeam, chestnut, and beech) constitute the birch homologous group. This grouping is primarily based on the extensive IgE cross-reactivity of allergen homologs to the major birch allergen Bet v 1. Birch pollen is the most dominant tree pollen in Northern and Central Europe and is a major cause of allergic rhinitis and, possibly, asthma symptoms. Over the last few decades, levels of birch pollen have risen and the period of exposure has increased due to climate changes. Subsequently, the prevalence of birch pollen sensitization has also increased. The cross-reactivity and sequential pollen seasons within the birch homologous group create a prolonged symptomatic allergy period beyond birch pollen alone. Furthermore, many plant food allergens contain homologs to Bet v 1, meaning that the majority of patients with birch pollen allergy suffer from secondary pollen food syndrome (PFS). As a result, the negative impact on health-related quality of life (HRQoL) in patients allergic to birch pollen is significant. The purpose of this manuscript was to narratively review topics of interest such as taxonomy, cross-reactivity, prevalence, clinical relevance, PFS, and HRQoL with regard to birch pollen allergy from a European perspective.

• Keywords
• alder, allergic rhinitis, birch, cross-reactivity, hazel,
• MeSH
• Allergens immunology   MeSH
• Antigens, Plant immunology   MeSH
• Betula immunology   MeSH
• Immunization MeSH
• Immunoglobulin E immunology   MeSH
• Humans MeSH
• Public Health Surveillance MeSH
• Prevalence MeSH
• Pollen immunology   MeSH
• Seasons MeSH
• Rhinitis, Allergic, Seasonal diagnosis   epidemiology   immunology   MeSH
• Symptom Assessment MeSH
• Cross Reactions immunology   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH
• Geographicals
• Europe epidemiology   MeSH
• Names of Substances
• Allergens MeSH
• Antigens, Plant MeSH
• Immunoglobulin E MeSH

PREMISE: Animal-pollinated plants face a high risk of pollen loss during its transfer. To limit the negative effect of pollen losses by pollen consumption and heterospecific transfer, plant species may adjust and stratify their pollen availability during the day (i.e., "schedule" their pollen presentation) and attract pollinators in specific time frames. METHODS: We investigated diurnal patterns of pollen availability and pollinator visitation in three coflowering plant species: Succisa pratensis with open flowers and accessible pollen, pollinated mainly by pollen-feeding hoverflies; Centaurea jacea with open flowers and less accessible pollen, pollinated mainly by pollen-collecting bees; and Trifolium hybridum with closed flowers and pollen accessible only after the active opening of the flower, pollinated exclusively by bees. RESULTS: The three plant species differed in the peak pollen availability, tracked by the visitation activity of their pollinators. Succisa pratensis released all pollen in the morning, while pollinator activity was still low and peaked with a slight delay. In contrast, C. jacea and T. hybridum had distinct pollen presentation schedules, peaking in the early afternoon. The pollinator visitation to both of these species closely matched their pollen availability. CONCLUSIONS: Stratifying pollen availability to pollinators during the day may be one of several mechanisms that allow coflowering plants to share their pollinators and decrease the probability of heterospecific pollen transfer.

• Keywords
• Centaurea jacea, Succisa pratensis, Trifolium hybridum, plant sexual reproduction, pollen presentation, pollen release schedule, pollen transfer, pollinator diurnal activity,
• MeSH
• Centaurea * MeSH
• Flowers MeSH
• Pollination * MeSH
• Pollen MeSH
• Plants MeSH
• Bees MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

For nearly a decade, the majority of the world's population has been living in cities, including a considerable percentage of people suffering from pollen allergy. The increasing concentration of people in cities results in larger populations being exposed to allergenic pollen at the same time. There is almost no information about spatial distribution of pollen within cities as well as a lack of information about the possible impact to human health. To obtain this increasing need for pollen exposure studies on an intra-urban scale, a novelty screening network of 14 weekly changed pollen traps was established within a large metropolitan area-Berlin, Germany. Gravimetric pollen traps were placed at a uniform street-level height from March until October 2014. Three important allergenic pollen types for Central Europe-birch (Betula), grasses (Poaceae), and mugwort (Artemisia)-were monitored. Remarkable spatial and temporal variations of pollen sedimentation within the city and the influences by urban local sources are shown. The observed differences between the trap with the overall highest and the trap with the overall lowest amount of pollen sedimentation were in the case of birch pollen 245%, grass pollen 306%, and mugwort pollen 1962%. Differences of this magnitude can probably lead to different health impacts on allergy sufferers in one city. Therefore, pollen should be monitored preferably in two or more appropriate locations within large cities and as a part of natural air quality regulations.

• Keywords
• Allergenic pollen, Germany, Gravimetric trap, Large city, Spatial distribution,
• MeSH
• Allergens analysis   MeSH
• Hypersensitivity MeSH
• Betula MeSH
• Air Pollutants analysis   MeSH
• Humans MeSH
• Poaceae MeSH
• Environmental Monitoring * MeSH
• Pollen * MeSH
• Rhinitis, Allergic, Seasonal MeSH
• Cities MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Geographicals
• Europe MeSH
• Germany MeSH
• Cities MeSH
• Names of Substances
• Allergens MeSH
• Air Pollutants MeSH