Esterases in pollen and stigma of Brassica

The dry type stigma of Brassica is covered with a continuous layer of cuticle. Cutinase and non-specific esterases may be involved in breakdown of this cuticle barrier during pollen-stigma interaction, but only a little is known about their nature and characteristics. We report here the presence of two distinct esterases from stigma and pollen of Brassica. A 33 kD esterase assayed using MU-butyrate substrate shows high activity in stigma papillae. A similar esterase from Tropaeolum pollen has been shown to possess active cutinase activity. The esterase activity in anther tissue is due to a 24 kD enzyme with substrate specificity toward acetate esters. Both enzymes require sulfhydryl groups for their catalytic activity. Immunogold labelling of antibodies raised against these esterases localised the proteins at the subcellular level. Antibodies for MU-butyrate hydrolase gave a positive signal in the cell walls of mature stigma papillae and in the tapetum and microspores during early stages of anther development. In the mature anther, a positive signal in the cytoplasm of pollen grains with some detectable localisation in the exine layer of the pollen wall was obtained. Similar results were obtained with acetate hydrolase antibodies. These esterases are thus spatially and temporally regulated in stigma and anther tissues.Abbreviations MU methyl umbelliferyl - pAbC anti-butyrate hydrolase polyclonal antibodies - pAbE anti-acetate hydrolase polyclonal antibodies     

Characterization of anther differentiation in cytoplasmic male sterile maize using a specific isozyme system (esterase)

Summary During anther development, characterized in maize plants with N cytoplasm, certain esterase isozymes in non-microspore cells decrease in amount with anther age and new isozymes appear in the developing microspores. In anthers from male sterile plants with cms T or cms C cytoplasm, neither of these changes in esterase patterns occurred. In anthers from plants with cms S cytoplasm, the decrease in the esterases of non-microsporogenous cells was observed but not the appearance of microspore esterases. In lines carrying cms S cytoplasm and nuclear restorer genes, esterase changes during anther development were as in normal fertile anthers. These results are discussed with respect to the phenomenon of cytoplasmic male sterility in the different maize genotypes.     

Seasonal distribution of pollen in the atmosphere of melbourne: an airborne pollen calendar

Environmental monitoring of pollen grains in the atmosphere of Melbourne has been achieved using Burkard volumetric traps. Twenty-two families of flowering plants and confiers were identified in the pollen counts. About 62% of these pollen grains belonged to trees, 20% to grasses and 9% to herbs and weedy plants. During spring and summer, the atmosphere contained about 70% of the total annual pollen count. Tree pollen, predominantly elm and cypress, occurred abundantly in late winter and spring, with grass pollen predominantly in spring and early summer. These three types of pollen grains occurred in significant amounts, together accounting for more than 60% of the total annual catch. A seasonal incidence chart (pollen calendar) for Melbourne based on 2 years observation has been constructed. This pollen calendar is useful in identifying sources of allergies against particular seasonal airborne pollen types. Comparison of the time of occurrence of a particular pollen type using the pollen calendar and the time of allergic symptoms, can lead to accurate diagnosis and preventive measures being taken. This study has confirmed that grass pollen is the major source of allergenic pollen in the external environment triggering hay fever and allergic asthma in spring and early summer in Melbourne, Australia.     

Effects of pollen competitive environment on pollen performance in Mirabilis jalapa (Nyctaginaceae)

 We examined the influence of pollen competitive environment on pollen performance in Mirabilis jalapa. We used the number of pollen grains and the number of pollen tubes per pistil as measures of pollen competition. Pollen germination, pollen tube penetration into the style, and pollen tube growth rates were used as measures of pollen performance. All three measures of pollen performance were affected by the competitive environment. Pollen germination was greatest at intermediate pollen load sizes. The percentage of germinated pollen grains that penetrated the stigma and grew into the style decreased with pollen load size. Pollen tube growth rate in the style was greater and more variable with larger numbers of pollen tubes in the style. Controlling for the degree of selection at the stigma indicated that pollen-pollen or pollen-style interactions were the likely causes of increased growth rates. Received: 28 October 1996 / Revision accepted: 24 January 1997     

Characterization of a new and thermostable esterase from a metagenomic library

A new gene encoding an esterase (designated as EstEP16) was identified from a metagenomic library prepared from a sediment sample collected from a deep-sea hydrothermal field in east Pacific. The open reading frame of this gene encoded 249 amino acid residues. It was cloned, overexpressed in Escherichia coli, and the recombinant protein was purified to homogeneity. The monomeric EstEP16 presented a molecular mass of 51.7 kDa. Enzyme assays using p-nitrophenyl esters with different acyl chain lengths as the substrates confirmed its esterase activity, yielding highest specific activity with p-nitrophenyl acetate. When p-nitrophenyl butyrate was used as a substrate, recombinant EstEP16 exhibited highest activity at pH 8.0 and 60 °C. The recombinant enzyme retained about 80% residual activity after incubation at 90 °C for 6 h, which indicated that EstEP16 was thermostable. Homology modeling of EstEP16 was developed with the monoacylglycerol lipase from Bacillus sp. H-257 as a template. The structure showed an α/β-hydrolase fold and indicated the presence of a typical catalytic triad. The activity of EstEP16 was inhibited by addition of phenylmethylsulfonyl fluoride, indicating that it contains serine residue, which plays a key role in the catalytic mechanism.     

Seasonal distribution of airborne pollen in the coastal plain of Israel

Airborne pollen was monitored in three major urban centers of the coastal plain of Israel during the years 1993–1995. Results show spatial and temporal variations among the three sites. Altogether, the number of identified species was rather low. Ornamental trees (Cupressaceae,Pinus, Olea, Casuarina, Ceratonia) and grasses, have constituted the main source of the pollen rain. A substantial contribution of the wild plants of the region was restricted toParietaria, Urtica, Mercurialis, Artemisia, grasses and members of the Chenopodiaceae and Amaranthaceae.     

西瓜花粉壁超微结构与花粉ATP酶细胞化学定位

研究了西瓜花粉壁超微结构以及单核花粉液泡化时期ATP酶活性超微细胞化学定位。花粉壁的外壁分为外层和内层 ,外层包括覆盖层、基粒棒和基足层等三层 ,内层只包含一层。外层电子密度相对较小 ,内层电子密度相对较大 ;外层与内层之间有缝隙。ATP酶活性反应产物主要分布在细胞质基质、质体、内质网和花粉内壁中     

A preliminary survey of airborne pollen in Madras City

The atmospheric pollen of Madras city was surveyed during a 1-year period (January–December 1995) with a vertical cylinder trap. A total of 32 pollen types were identified, among which nine were present throughout the year. These belonged to Poaceae,Casuarina equisetifolia Foster and Foster f.,Prosopis juliflora (SW.) DC.,Acalypha indica L.,Parthenium hysterophorus L., Cyperaceae,Cocos nucifera L., Amaranthaceae, andTypha angustata Borry and Chaub. Among the identified pollen, 61.05% belonged to trees, 21.01% to grasses, 11.65% to herbs and 6.27% to shrubs. Anemophilous pollen contributed about 52.87% to the total while entomophilous and amphiphilous pollen contributed 38.89 and 8.22%, respectively. Pollen belonging to Poaceae were found to be most predominant in the air of Madras city followed byCasuarina equisetifolia andProsopis juliflora.     

Airborne pollen calendar of the central region of Bursa (Turkey)

This report describes qualitatively and quantitatively the level of pollen in the atmosphere in the central region of Bursa. Turkey. In 1991, the season of maximum pollen concentration was from April to June, with a prevalence of arboreal pollen during the initial months, and of pollen from herbaceous plants in the latter months. During the year of research, 24 taxa of arboreal and 12 taxa of herbaceous pollen grains were collected and identified. In the region investigatedPinus, Cupressaceae/Taxaceae,Abies nordmanniana, Platanus orientalis, Olea europaea, Gramineae, Urticaceae, Chenopodiaceae/Amaranthaceae,Artemisia and Compositae were responsible for the greatest amounts of pollen. Some important allergenic pollens such asOlea europaea, Gramineae and Urticaceae were also found in high concentration. In this study, a pollen calendar for the region is presented.     

Ultrastructural study of Saffron pollen

Abstract

Pollen of Saffron (Crocus sativus L.), a sterile autotriploid plant was studied using scanning and transmission electron microscopy. The pollen of mature anthers had grains not containing pores or furrows, a discontinuous thin exine and a very thick intine crossed by tubules containing granular electron-dense material. Electron transparent material and lipid bodies were abundant in the cytoplasm which also contained a large number of vesicles. A high percentage of pollen grains showed anomalies.     

Pistil strategies controlling pollen tube growth

The progamic phase appears especially well suited for pollen-pistil interaction. During this phase the pistil supports pollen germination and tube growth, and provides an adequate environment, nutrition and directional cues. However, this support does not occur indiscriminantly and some mechanisms operating in the pistil constrain pollen tube growth. An active, regulated constraint is the self-incompatibility reaction, but moderate restrictions of pollen tube growth also occur in compatible matings. These moderate restrictions involve reduced support by the pistil and they operate through two main strategies; one is by decreasing the amount of support and the other is by varying the time at which this support is provided. In this minireview, we examine the evidence that is accumulating for both support and constraint of pollen tube growth by the pistil and discuss the benefits of this dual system.     

The relationship between airborne pollen distribution and the frequency of specific pollen sensitization at two climatically different locations in Switzerland

Pollen data reported from the two monitoring stations of Locarno-Monti, on the southern slopes of the Alps, and Zurich on the northern slopes of the Alps, for the years 1989–1993 were compared with meteorological data from the corresponding locations and with the prevalence of pollinosis and frequency of specific pollen sensitization in patients with pollinosis. It was so discovered that the recorded quantity of allergenic pollen types (Alnus, Corylus, Betula, Fraxinus, Poaceae, Castaneae,Olea andArtemisia) south of the Alps is higher by a factor of 2.9 than that north of the Alps. These differences are due to the distinctly milder climate in the canton of Ticino (south of the Alps) showing higher annual mean temperatures, more sunshine duration and less precipitation days with higher amounts of precipitation. The allergological data show additionally that the summer pollinosis, caused byCastanea andOlea, is probably responsible for the differing prevalence of pollinosis at the two sites. Finally, we can summarize that in Switzerland pollen from Poaceae, Betulaceae and Oleacea are the most important for pollinosis.     

Growth and development of conifer pollen tubes

Conifer pollen tubes are an important but underused experimental system in plant biology. They represent a major evolutionary step in male gametophyte development as an intermediate form between the haustorial pollen tubes of cycads and Ginkgo and the structurally reduced and faster growing pollen tubes of flowering plants. Conifer pollen grains are available in large quantities, most can be stored for several years, and they grow very well in culture. The study of pollen tube growth and development furthers our understanding of conifer reproduction and contributes towards our ability to improve on their productivity. This review covers taxonomy and morphology to cell, developmental, and molecular biology. It explores recent advances in research on conifer pollen and pollen tubes in vivo, focusing on pollen wall structure, male gametophyte development within the pollen wall, pollination mechanisms, pollen tube growth and development, and programmed cell death. It also explores recent research in vitro, including the cellular mechanisms underlying pollen tube elongation, in vitro fertilization, genetic transformation and gene expression, and pine pollen tube proteomics. With the ongoing sequencing of the Pinus taeda genome in several labs, we expect the use of conifer pollen tubes as an experimental system to increase in the next decade.     

The genetical control and tissue-specificity of esterase isozymes in hexaploid wheat

A comparative genetic analysis of esterase (E.C.3.1.1.1) isozymes of wheat cultivar Chinese Spring in endosperm, embryo, coleoptile, leaf and root tissues revealed eight sets of isozymes characterised by different tissue specificities, pI ranges and the chromosomal locations of their controlling genes. This data was considered together with previously published work, resulting in a proposed rationalization of nine sets of wheat esterase isozymes. Although this classification included two sets of isozymes controlled by genes on the short arms of homoeologous group 3 chromosomes and three sets on the long arms of the same chromosomes, for which no recombination evidence of genetic distinctness has been obtained among either group, it is argued that the different characteristics of the various sets warrant retention of separate set nomenclatures. Previously unreported esterase genes includeEst-9, a low pI, monomeric, embryo-specific group with controlling genes on chromosomes 3BS and 3DS and two further members ofEs-1,Est-H1 inHordeum vulgare andEst-S ^l1 inAegilops longissima.     

Ultrastructural investigations on Lycopersicum peruvianum pollen activation and pollen tube organization after self-and cross-pollination

No differences have been observed in vivo between Lycopersicum peruvianum compatible and incompatible pollen during activation and pollen tube emission and organization, that is until 4 h and 30 min after pollination. During pollen activation the main events are the setting free of rough endoplasmic reticulum (RER) cisterns which were stacked in the mature pollen, the increase in the number of polysomes, and a great activity of the dictyosomes. Immediately after germination of the vegetative nucleus and the generative cell move into the tube, the generative cell diviting to form the male gametes; the tube then becomes organized in four zones. This series of changes is similar to what has already been observed in vitro except that in vitro the generative cell remains undivided and the whole process from seeding to tube organization takes 3 h instead of 4 h and 30 min after pollination, as it does in vivo. Our findings are compatible with the main models of the tube inhibition mechanism proposed till now.Abbreviations RER rough endoplasmic reticulum - GC generative cell - VN vegetative nucleus - GP germinative pore Research performed under C.N.R. (Italian National Research Council) program Biology of Reproduction     

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.     

Occurrence of ofloxacin ester-hydrolyzing esterase from Bacillus niacini EM001

A Bacillus niacini strain (EM001) producing an ofloxacin ester-enantioselective esterase was isolated from the soil samples collected near Taejon, Korea. The cloned gene showed that the esterase EM001 composed of 495 amino acids corresponding to a relative molecular weight (M_r) of 54,098 kDa. Based on the M_r and the protein sequence, the esterase EM001 was similar to p-nitrobenzyl esterase from Bacillus subtilis with an identity of 41.8%. The optimum temperature and pH of the purified His-tagged enzyme were 45 °C and 9.0, respectively. The purified esterase EM001 hydrolyzed preferably (R)-ofloxacin propyl ester than (S)-form ester at the initial reaction phase with an ee_P of 67% until the conversion rate become up to 35%.     

Stimulation of pollen tube growthin vitro by dicarboxylic acids

Summary Effect of eight dicarboxylic acids and three monocarboxylic acids on pollen growth ofCamellia japonica was tested. While monocarboxylic acids inhibited pollen germination and pollen tube elongation, dicarboxylic acids, namely oxalic, succinic, suberic, adipic, sebacic, traumatic cis-1,2-cyclohexane dicarboxylic, and 3,3-diethyl glutaric acids stimulated pollen tube elongation stronger than indoleacetic acid.     

蓝花丹开花生物学观测及花粉储存研究

对四川引种栽培的蓝花丹（Plumbago auriculata Lam.）花粉与柱头形态、花部特征及开花物候进行了系统观测,并对其花粉的采集时间与储存温度进行了初步研究。结果显示：（1）两种类型花粉和柱头形态均具有较大差异,短花柱型（S型）花粉的极轴长P值和赤道轴长E值均显著大于长花柱型（L型）花粉,L型柱头则明显长于S型,且两种花粉的纹饰和柱头的瘤状突起物形态也明显不同;（2）蓝花丹具有较高的开花同步性指数（为0.89）,但相对开花强度不高,属于中等强度;（3）蓝花丹两种花型在花蕾半开放时采收花粉,其活力最高,L型花粉活力可达85.24%±4.22%,S型可达87.74%±2.95%;（4）L型与S型花粉分别于25℃干燥0.5 h和1 h后再低温储存,其活力保持更好;（5）干燥后的花粉在-86℃条件下保存效果最好,储存30 d后L型花粉活力高达66.51%±0.85%、S型达69.07%±1.57%。本研究表明蓝花丹二型植株在生殖资源分配上存在明显差异,这种差异一方面导致花粉大小和形态及其所需干燥时间的不同,另一方面导致二型花柱头表现出明显不同的特征,这些差异性的结构是否参与了蓝花丹自交不亲和反应的识别过程,还有待进一步研究。此外,较低的开花强度会造成虫媒传粉困难,这可能是蓝花丹自然结实率极低的重要因素之一。