Dynein-related polypeptides in pollen and pollen tubes

 Microtubules in pollen tubes are evident within the vegetative and generative cell cytoplasm. This observation led to the formulation of several hypotheses regarding the role of microtubules in cytoplasmic movement and the migration of the vegetative nucleus/generative cell along the pollen tube. The study of microtubular motor proteins in pollen tubes followed the discovery and characterization of an immunoreactive homolog of mammalian kinesin in tobacco pollen tubes. Recent identification of dynein-related polypeptides in pollen tubes of Nicotiana tabacum and pollen of Ginkgo biloba is a significant step in the definition of the role of microtubule function within pollen and pollen tubes. Received: 31 May 1996 / Revision accepted: 26 July 1996     

Regional and extra-local pollen in Tundra pollen samples

Patterns of pollen spectra formation in the tundra zone of Eurasia were considered. Changes in total pollen concentration were traced in subfossil pollen samples of the tundra zone. The data on subfossil pollen spectra were used to evaluate the proportion between local and regional plus extra-local components of tundra pollen samples as well as the changes in concentration of pollen of Scots and Siberian stone pines as well as of tree and shrub birches. The diameter of dwarf birch pollen was determined in different tundra subzones of Western Siberia. The role of extra-local and regional pollen was considered for all vegetation subzones of tundra.Translated from Izvestiya Akademii Nauk, Seriya Biologicheskaya, No. 1, 2005, pp. 88–99.Original Russian Text Copyright © 2005 by Vasilchuk.     

Phytic acid in pollen

Phytic acid has been identified by paper electrophoresis and NMR spectroscopy in extracts of pollen from Petunia hybrida. In this species pollen wa     

花粉破壁法对花粉蜂蜜酒中氨基酸含量的影响

以蜂蜜为主料,加入花粉,经过调配、发酵、过滤、陈酿后获得氨基酸含量丰富的酒精饮料。花粉破壁分别采用超声破碎法、酶法和温差破壁法这几种不同方式处理,并添加于蜂蜜发酵液中,经酒精发酵,制得富含活性成分的花粉蜂蜜酒。最后利用毛细管电泳法来测定成品酒中的氨基酸,通过分析优化出最佳的花粉破壁方法。研究结果表明花粉经过温差破壁法处理后加入发酵液中,其成品的氨基酸含量最高。该产品不仅营养价值高,风味独特,而且还具有良好的保健作用。     

Small RNAs in pollen

In plants, each pollen mother cell undergoes two rounds of cell divisions to form a mature pollen grain, which contains a vegetative cell(VC) and two sperm cells(SC). As a companion cell, the VC carries the SCs to an ovule by germinating a pollen tube. In-depth sequencing analyses of mature pollen showed that micro RNAs(mi RNAs) and short interfering RNAs(si RNAs) are present in both the VC and SCs. Additionally, epigenetically-regulated transposable elements(TEs) are reactivated in the VC and these TE m RNAs are further processed into 21-nt epigenetically reactivated si RNA(easiR NA) in SCs, which prevent 24-nt si RNA accumulation and sequester mi RNA loading. Small RNAs are thought to move from the VC to SCs, where they regulate gene expression and reinforce TE silencing. Here, we summarize current knowledge of the biogenesis and function of mi RNAs, si RNAs, and easi RNAs in pollen, emphasizing how these different small RNAs coordinately contribute to sperm cell formation and TE silencing.     

From anther and pollen ripening to pollen presentation

The events and processes occurring between pollen maturation, opening of the anther and presentation of pollen to dispersing agents are described. In the final phases of pollen development, starch is always stored; this occurs before the anther opens. Depending on the species, this starch may be totally or partially transformed into: (a) other types of polysaccharides (fructans and rarely callose); (b) disaccharides (sucrose); (c) monosaccharides (glucose and fructose, all situated in the cytoplasm. While awaiting dispersing agents and during dispersal, polysaccharides, especially fructans, and sucrose may be interconverted to control osmotic pressure and prevent loss and uptake of water. Opening of the anther is preceded by disappearance of the locular fluid and in many cases by partial dehydration of the pollen. Pollen generally has a water content between 5 and 50%. Pollen with a high water content may or may not be able to control water retention during pollen exposure and dispersal. Pollen may be dispersed in monads or grouped in pollen dispersing units by the following mechanisms: (i). tangling of filamentous pollen; (ii). adhesion by viscous substances (pollenkitt, tryphine, elastoviscin) derived from the tapetum; (iii). common walls. When the anther opens, the pollen may be dispersed immediately, remain until dispersed (primary presentation), or be presented to pollinators in another part of the flower (secondary presentation).     

Androgenesis in isolated pollen cultures ofNicotiana tabacum: Dependence upon pollen development

Summary The influence of the stage of pollen development and of the growth conditions of donor plants on the performance of cultures of isolated pollen fromNicotiana tabacum, var. Badischer Burley has been studied. The method described includes cold treatment (4–5 °C for 3 days) and a pre-culture of the anthers for 7 days at 24 °C before the pollen is isolated. With this system reproducible results were obtained with pollen at the early binucleate stage collected from plants 11–13 weeks old. Another prerequisite for reproducibility is that the donor plants must have been grown for eight weeks in soil with an additional supply of mineral salts. Furthermore, the production of haploids by these pollen cultures was strongly influenced by the photoperiodic and temperature regime experienced by the donor plants; it was best (0.07%) with pollen from short-day plants (8 hours light per day at 18 °C) and rather weak (0.015%) with pollen from long-day plants (16 hours light per day at 24 °C). In contrast to other reports, haploid production from anther cultures was not influenced by the photoperiod or temperature.Cytological studies undertaken at the end of the pre-culture period showed that there were no differences in the percentage of potential embryos for the stages of the late uninucleate, 1. pollen mitosis and early binucleate pollen of long-day plants (1.5%). This value was considerably higher with pollen from short-day plants (7–9%), indicating that short-day conditions at 18 °C of the donor plants are favourable for the induction of androgenesis. However, only the potential embryos formed by the pollen at the initial binucleate stage were able to continue androgenetic development after isolation.     

Changes in nutritional composition from bee pollen to pollen patty used in bumblebee rearing

Pollen patties are generally supplied to augment the nourishment of honey bee or bumblebee colonies during late winter or early spring. In the present study, we examined nutrient content of bee collected pollen (BP) and pollen patties (PT) prepared from those bee collected pollens in order to understand the chemical compositional change of pollen to pollen patty and figure out the possible benefits for bee’s health. Protein and fat contents of pollen patties were found lower than that reported for the respective bee pollens. Amino and fatty acids followed the same trend for the simple logical reason. In contrast, carbohydrate contents of pollen patties were found much higher than the bee pollen. The addition of sugar solution in the process of pollen patty preparation could presumably explain the change. Another possible determinant factor of bee’s preference of feed protein to fat ratio was found the highest for PT 2 (5.5) followed by PT 1 and BP 2 (4.1), BP Ref. (2.9) and the least value obtained for BP 1 (2.2). Additionally, we discuss the possible health benefits if the bee collected pollen is used as a human food supplement.     

A change from grass pollen induced allergy to tree pollen induced allergy: 30 years of pollen observation in Switzerland

Pollen monitoring with a Hirst like pollen trap for 30 years in Basel, Switzerland allows understanding of the behaviour of the different plants producing allergenic pollens. It becomes evident that in this time period the different tree pollen like Hazel and Birch increased, whereas in the control, the observed amount of a herb pollen like Artemisa did not change. Moreover, it was observed that in the different trees flowering took place earlier namely at the beginning of the year. This was especially impressive for Hazel, where flowering was shifted ofmore than one month. These aerobiological observations were supported and confirmed by some epidemiological studies, showing that tree pollen allergy has become more important in the last years compared to grass pollen allergy and herb pollen allergy. The reason for the increase of tree pollen counts and the shift in the flowering time depends on the observed increase of the annual temperature, an increased input of nutrients like CO₂or NO_x but probably also a real increase of certain trees, like birch for example, in parks and avenues. This revised version was published online in June 2006 with corrections to the Cover Date.     

Sodium thioglycollate enhances pollen germination and pollen tube elongation in cruciferous species

Sodium thioglycollate is a reducing agent used in microbiological growth media to enhance the growth of anerobic, microaerophilic, and facultative organisms, and in eukaryotic tissue extraction buffers to inhibit damaging oxidative reactions. Sodium thioglycollate was added to a semi-solid pollen germination medium to evaluate its effects on in vitro pollen germination and pollen tube elongation, based on the assumption that conditions within stylar tissues are less aerobic than in ambient conditions. We observed significant increases in the percent germination and pollen tube elongation of both crop and weedy mustard family species, on a medium containing 2.2 mM sodium thioglycollate. This suggests that sodium thioglycollate may be a useful amendment to semi-solid media and to solutions that are used to study pollen vigor, physiology, or gene expression, and to bioassay sensitivities of different species or genotypes to diverse physical and chemical factors.     

空气致敏花粉污染研究进展

对空气致敏花粉污染概念的提出 ,空气致敏花粉污染的特点和影响因素 ,花粉采集方法的改进以及空气致敏花粉污染的研究进展等方面进行了总结 ,指出了研究中存在的问题 ,并对研究前景进行了展望     

tRNA synthesis in germinating pollen

The synthesis of tRNA was demonstrated in pollen ofNicotiana tabacum L. according to the incorporation of labeled uracil, adenosine and guanosine during 4 h of germination. tRNA was extracted from postribosomal supernatant and purified by polyacrylamide gel electrophoresis. The incorporation of guanosine was about 1.68 times higher than that of adenosine. This finding indicates that the whole tRNA chain is formed in pollen tubes.     

Triporate pollen in the Arecaceae

Triapertury is rare in monocotyledons. The well-defined, regularly spaced, circular porate apertures that occur in Arecaceae: Areca klingkangensis from Borneo, and species of the West African genus Sclerosperma, appear to be unique in monocotyledons. There is evidence to suggest that tripory in Arecaceae has been derived from trichotomosulcy, although in Areca equatorial zonosulcy may have an important role. The apical triporate, and zonosulcate pollen of Areca are described, as well as examples of mono- and trichotomosulcate pollen within the genus. The sub-apical distal triporate pollen of Sclerosperma gilletii and S. mannii are described. Notably, in Sclerosperma pollen, aperture position at post-meiotic tetrad stage follows the rare ‘Garside's rule’ (four groups of three apertures), previously only demonstrated for Proteaceae and Olacaceae. Possible reasons for the occurrence of these rare triporate pollen phenomena in palms are considered. The bearing this may have on the transition from the distal polar position of the single sulcus, to the radial symmetry of the triaperturate condition in many dicotyledons is discussed in comparison with other examples of triapertury in monocotyledons.     

Gene expression in allergenic pollen

The molecular mechanism of gene expression for pollen specificity is not yet fully known. However, it is an exciting area with great potential and has a wide scope of application in the field of molecular biology, breeding systems, biotechnology etc. The main aim of this write-up is to review some of the interesting achievements made through studies like gene expression in allergic pollen and the research which will make a way towards practical application of pollen molecular biology in identifying and isolating the genes responsible for all allergic disorders reported among various individuals. This revised version was published online in June 2006 with corrections to the Cover Date.     

Aerobic fermentation in tobacco pollen

We characterized the genes coding for the two dedicated enzymes of ethanolic fermentation, alcohol dehydrogenase (ADH) and pyruvate decarboxylase (PDC), and show that they are functional in pollen. Two PDC-encoding genes were isolated, which displayed reciprocal regulation: PDC1 was anaerobically induced in leaves, whereas PDC2 mRNA was absent in leaves, but constitutively present in pollen. A flux through the ethanolic fermentation pathway could be measured in pollen under all tested environmental and developmental conditions. Surprisingly, the major factor influencing the rate of ethanol production was not oxygen availability, but the composition of the incubation medium. Under optimal conditions for pollen tube growth, approximately two-thirds of the carbon consumed was fermented, and ethanol accumulated into the surrounding medium to a concentration exceeding 100 mM.