A comparative analysis of pollen limitation in flowering plants

We conducted a comparative analysis to determine life history and ecological correlates of pollen limitation among 224 species of animal-pollinated flowering plants. To test predictions concerning the occurrence of pollen limitation, species were classified categorically for six life-history traits (self-compatible vs. self-incompatible, autogamous vs. non-autogamous, specialized vs. unspecialized floral morphology, nectariferous vs. nectarless, monocarpic vs. polycarpic, herbaceous vs. woody) and two ecological conditions (presence in open vs. forested habitats and temperate vs. tropical biomes). Pollen limitation of species in contrasting categories was compared using non-parametric tests (TIPs analysis) and phylogenetically-independent contrasts (PICs). The results of TIPs and PICs analyses were generally congruent, although fewer significant contrasts were evident with PICs, probably because of low statistical power. Overall the results suggest that the influence of phylogenetic history on the intensity of pollen limitation was not particularly strong. Nonetheless, significant variation in the degree of pollen limitation was demonstrated among seven angiosperm families suggesting some phylogenetic component to the phenomenon. With both TIPs and PICs, pollen limitation was less intense in self-compatible and autogamous species. TIPs analysis demonstrated that herbaceous, nectariferous, and temperate species were less likely to be pollen-limited, but using PICs this could only be corroborated for those that were self-incompatible. None of the traits were singularly unambiguous predictors of pollen limitation, possibly reflecting the stochastic nature of pollinator service.     

Biogenesis and function of the lipidic structures of pollen grains

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

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     

Elemental and biochemical markers of stigma receptivity in sunflower

Stigma development in sunflower is accompanied with an accumulation of calcium (33 %), potassium (37 %) and boron (62 %) in mature stigma as compared to stigma at bud stage, thereby demonstrating their essential roles in attaining receptivity. Membrane-bound calcium accumulation is enhanced on the pellicle and is also evident in the cytoplasm accompanying stigma maturation. Total soluble carbohydrate content increases in the staminate stage (55 %) as compared to bud stage. Glucose and fructose are the major monosaccharides and their contents are maximum in the staminate stage. Total lipid content also increases with the passage of stigma development. Erucic acid (22:1) is expressed specifically in the bud and staminate stages. A variation in the contents of triacylglycerides and free fatty acids, and expression of fatty acyl esterases in mature stigma have been correlated with biochemical events associated with signalling mechanisms. Lastly, enhanced expression of two hydrolytic enzymes, namely β-1,3 glucanase and fatty acyl ester hydrolase, has been observed to correlate with stigma maturation. Present findings, thus, provide new information on the structural and biochemical changes marking various signalling events associated with successful pollen–stigma interaction.     

Cotton embryogenesis: The pollen tube in the stigma and style

Summary The ultrastructure and composition of the pollen tube of cotton (Gossypium hirsutum) growing in the tissues of the stigma and style of the flower were examined. The distal portion of the tube is densely cytoplasmic and contains the vegetative nucleus and the two sperms. The vegetative nucleus is highly convoluted and the membrane contains many pores and connections with the ER. No organized nucleolus is present but 4–6 membrane-bound, protein containing bodies are found in the nucleus. Mitochondria containing numerous cristae are abundant in the cytoplasm. Dictyosomes are also plentiful and are engaged in the production of many large vesicles. Rough ER is conspicuous and polysomes are found in the cytoplasm. Plastids are few in number, poorly developed, and contain little starch. Many uniform, small vesicles are found throughout the cytoplasm. Lipid bodies frequently with small vesicles associated with them are found in the tube. In the proximal region vacuoles form and the cytoplasm becomes pressed against the wall. In the transition zone the ER frequently becomes distended and filled with protein. The wall has two distinct layers: one strongly PAS positive, the other faintly PAS positive. The inner wall is apparently formed by the deposition of large dictyosome vesicles. Plug structure and development were studied.     

Day-night cycle of lipidic composition in rat cerebral cortex

A study of the lipidic pattern of the cerebral cortex of the normal adult rat during the daynight cycle was carried out. The changes observed were the following: phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol and phosphatidylserine plus phosphatidic acid showed a peak at 16:00 hr possibly due to a general increase in phospholipid biosynthesis. During the nocturanl period the variations of phosphatidylcholine and phosphatidylethanolamine were not clearly observe, they might be due to an increase in the interconversion or exchange reaction, since the ratio phosphatidylcholine/phosphatidylethanolamine showed a significative change at 04:00 hr. This occurred because small but opposite changes in both phospholipids were observed, suggesting an increase in the methylation reactions of phospholipids. Cardiolipin showed a significant peak at 04:00 hr. Plasmalogens exhibited significative changes, an important diminution at 16:00 hr and a prominent peak at 24:00 hr. Cholesterol levels were high during the light period and low in the dark one. Cerebrosides and gangliosides showed no day-night variations. The changes observed indicate a phenomenon of biological rhythmicity synchronized by the photoperiod, suggesting that these fluctuations could act as physiological modulators of the properties and functions of the nerve cell membrane.     

A comparative analysis of nested subset patterns of species composition

We present a broad comparative assessment of nested subsets in species composition among ecological communities. We assembled presence-absence data from a broad range of taxa, geographic regions, and spatial scales; and subjected this collection of datasets to common analyses, including a variety of metrics for measuring nestedness and null hypotheses against which to evaluate them. Here we identify ecological patterns in the prevalence and strength of nested subset structure, and assess differences and biases among the available methodologies. In all, we compiled 279 presence-absence matrices, of which 163 do not overlap in their coverage of species and sites. The survey includes studies on vertebrates, arthropods, mollusks, plants, and other taxa; from north temperate, tropical, and south temperate latitudes. Our results were as follows. Statistically significant nestedness was common. Assemblages from landbridge archipelagos were strongly nested, and immigration experiments were least nested. This adds further empirical support to the hypothesis that extinction plays a major role in producing nested structure. Nestedness was positively correlated with the ratio of the areas of the largest and smallest sites, suggesting that the range in area of sites affects nestedness. Taxonomic differences in nestedness were weak. Higher taxonomic levels showed stronger nesting than their constituent lower taxa. We observed no effect of distance of isolation on nestedness; nor any effects of latitude. With regard to methodology, the metrics Nc and Ut yielded similar results, although Nc proved slightly more flexible in use, and deals differently with tied sites. Similarities also exist in the behavior of N0 (“N”) and Up, and between N1 and Ua. Standardized nestedness metrics were mostly insensitive to matrix size, and were useful in comparative analyses among presence-absence matrices. Most metrics were affected by the proportion of presences in the matrix. All analyses of nestedness, therefore, should test for bias due to matrix fill. We suggest that the factors controlling nested subset structure can be thought of as four filters that species pass to occur at a site: a sampling filter, a distance filter, a habitat filter, and an area filter – and three constraints on community homogeneity: evolutionary history, recent history, and spatial variation in the environment. The scale of examination can also have important effects on the degree of nestedness observed. Received: 13 September 1996 / Accepted: 16 September 1997     

A comparative study on the distribution of non-specific esterase amongst the various constituents of retinas of some vertebrates

A wide coverage of the retinae of a large number of animals (Calotes, Varanus, Naja, Athene, Passer, Streptopelia, Psittacula and Funambulus) from the point of view of the histoenzymological distribution of non-specific esterase amongst the various constituents reveals mostly identical patterns. They are as follows: 1. Outer segments - positive in all cases. 2. Outer plexiform layer - equipped with enzymatic activity in all the instances. 3. Inner nuclear layer - thin cytoplasmic rim of the neurons characterized by positive activity; the nuclei of the neurons are completely negative. 4. Inner plexiform layer - this layer is endowed with the enzymatic activity. 5. Ganglion cells - negative in all cases. 6. Nerve fibres of the layer of nerve fibres, situated adjasent to ganglion cells are positive in all the animals; in case of squirrel oligodandroglial cells present in the region have demonstrated activity of a high order. On of the high-lights of the present contribution is demarcation of the inner plexiform layer into three stratified zones, equipped with enzymatic activity in Calotes, Streptopelia, Naja and Funambulus. Such stratifications are not seen in Varanus, Passer and Psittacula. The significance of the various patterns and the equipment of the enzyme in various constituents at various locals have been discussed in relation to the metabolic functions, zone-wise and interzone-wise in visual processes of various animals.     

A comparative biochemical study of conifer pollen allergens

In the order Coniferales, only the family Cupressaceae is regarded as being a significant source of airborne allergens, withJuniperus ashei characterized as the most significat aeroallergen. Pollen of the closely related speciesJ. virginiana has been shown to cross-react withJ. ashei pollen, however,J. virginiana pollen is not considered an important aeroallergen. Although there have been several reports of allergies toPinus pollen, the pollen of this genus is regarded as hypoallergenic. Our previous studies have shown that pollen extracts ofJ. ashei, J. virginiana, J. pinchotii, Cupressus macrocarpa, Pinus echinata andP. taeda all contained several proteins with the same molecular weights including the reported allergen ofJ. ashei. The present study compared the biochemistry ofJ. ashei, J. virginiana andP. echinata pollen. A time course experiment ofJ. ashei, J. virginiana andP. echinata showed thatJ. ashei released a greater quantity of protein within the first minute of moistening. SDS-PAGE analyses showed that the reported allergen ofJ. ashei pollen extracts was released in large quantities within the first minute of extraction. It was also determined that individual pollen grains ofP. echinata contained a greater quantity of protein than the pollen ofJ. ashei andJ. virginiana, but due to the large size of pine pollen there was less protein per gram of pollen. Lipid analysis of these three taxa showed that the pollen ofP. echinata contained more lipid per grain and per gram of pollen. Results indicate that the rapid release of the reported allergen fromJ. ashei pollen contributes to the allergenicity of this species compared to bothJ. virginiana andP. echinata.     

Intracellular distribution of enzymes associated with nitrogen assimilation in roots

The cellular distribution of enzymes involved in nitrogen assimilation: nitrate reductase (EC 1.6.6.2), nitrite reductase (EC 1.6.6.4), glutamine synthetase (EC 6.3.1.2), glutamate synthase (EC 2.6.1.53), and glutamate dehydrogenase (EC 1.4.1.3) has been studied in the roots of five plants: maize (Zea mays L. hybrid W 64A x W 182E), rice (Oryza sativa L. cv. Delta), bean (Phaseolus vulgaris L. cv. Contender), pea (Pisum sativum L. cv. Demi-nain), and barley (Hordeum vulgare L.). Initially, cell organelles were separated from soluble proteins by differential centrifugation. Cell organelles were also subjected to sucrose density gradients. The results obtained by these two methods indicate that nitrite reductase and glutamate synthase are localized in plastids, nitrate reductase and glutamine synthetase are present in the cytosol, and glutamate dehydrogenase is a mitochondrial enzyme.     

偏头痛相关酶和KEGG通路分析

搜集与偏头痛相关的编码酶的基因,利用KEGG通路分析目标基因的分布和功能,促进偏头痛遗传学研究和新药靶点研究。以＂gene name＂AND migraine检索PUBMED数据库,从原始文献中搜集并整理偏头痛相关酶基因数据,用DAVID在线分析工具对数据进行处理。搜索得到31个偏头痛酶基因,对7条KEGG代谢通路进行了分析：色氨酸代谢通路、酪氨酸代谢通路、精氨酸和脯氨酸代谢通路、叶酸一碳单位循环代谢通路、药物代谢通路、外源物质细胞色素P450代谢通路、肾素血管紧张素代谢通路。其中药物代谢通路包括9个药物,又以高选择性5-羟色胺重摄取抑制剂西酞普兰的应用前景最大。DDC、DBH、MTHFD1等6个偏头痛相关基因需要完善多态性研究。CYP450和单胺氧化酶在偏头痛的病理和治疗中都占有重要的地位。通过分析疾病相关酶基因的代谢通路,有助于了解疾病的分子病理基础,并为新药设计提供可靠靶点。     

Wall-softening enzymes in the gynoecium and pollen of Hemerocallis fulva

Summary Variations in extractable cellulase and pectinase were followed during development of Hemerocallis (day lily) flowers. A peak in cellulase activity occurs in the pistil just prior to anthesis, followed by a 62% diminution in the enzyme activity at the time of anthesis. Cellulase activity, per mg protein, is about twice as high in the upper (stigma) portion as in the middle and lower one-third of the pistil tissues. No pectinase activity was detected in the pistil at all stages of development. Extractable pectinase is present at a maximum level in the very young ovary; it decreases rapidly as the ovary develops. Cellulase remains at a moderate level of activity throughout the development of the ovary, except for an increase of about 50% at pollination. Soluble cellulase and pectinase are found in mature pollen. The changes in the cell-wall hydrolytic enzymes in the pistil were pollen-tube growth. It may also promote changes in the cell walls of the pistil cells, although metabolism of the middle lamella during pollen germination is primarily controlled by pollen pectinases.A contribution of the Florida Agricultural Experiment Station, Journal Series No. 3070.     

Purification of maize pollen exines and analysis of associated proteins

Zea mays (maize) pollen exines have been purified with the use of differential centrifugation and sucrose gradients, followed by mild detergent and high salt treatment. The final exine fraction is highly purified from other organelles and subcellular structures as assayed by transmission electron microscopy. Using mature maize pollen as the starting material, 0.2 to 0.3% of the total pollen protein remained associated with the exine fraction throughout the purification. Seven abundant sodium dodecyl sulfate-extractable proteins are detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis in the final fraction. Amino acid analysis reveals that one of the proteins contains a substantial amount of hydroxyproline, a characteristic of some primary cell wall proteins. The amino acid composition of the 25-kD protein strongly implies that it is an arabinogalactan protein. When exines are purified from earlier pollen developmental stages, a subset of the proteins found in the mature pollen exine is seen.     

Sugar composition of pollen grain and pollen tube cell walls

The sugar composition of pollen grain and pollen tube cell walls was studied for Camellia japonica, C. sasanqua, C. sinensis, Tulipa gesneriana and Lilium longiflorum. In all species, the main components of pollen grain walls were arabinose, galactose, glucose and uronic acid. On the other hand, the pollen tube walls consisted mostly of glucose. The pollen tube wall of C. japonica was fractionated into hemicellulose, α-cellulose and pectic substance fractions in yields of 61, 19 and 3 %, respectively. The hemicellulose fraction was composed essentially of glucose. The sugar composition of the pollen tube wall was not influenced by the nature of exogenously supplied sugars. Rapid growth of the pollen tube seemed to correlate with the synthesis of hemicellulosic glucan.     

Serine esterases are required for pollen tube penetration of the stigma in Brassica

. We have investigated the diversity of serine esterases in pollen and stigma tissues of Brassica napus and the role of these enzymes in pollen germination and pollen tube penetration of the stigma. The serine esterase-specific inhibitor diisopropyl fluorophosphate was used as a probe in a tritiated form, [³H]-DIPF, to determine the number and diversity of serine esterases in crude protein extracts from pollen and stigma. Seven serine esterases were identified in pollen and at least seven serine esterases were identified in stigma. The most abundant enzymes had molecular weights of 30-50 kDa. In the pollen extract a serine esterase was detected with the same molecular weight, 22 kDa, as an esterase previously shown to be a cutinase. Only one serine esterase (40 kDa) appeared to be shared between pollen and stigma extracts. Butyrate esterase activity in pollen and stigma extracts was assayed using p-nitrophenyl butyrate (PNB), an ester substrate frequently used in 'cutinase' assays. Total PNBase activity in pollen and stigma extracts was shown to be significantly reduced by the serine esterase inhibitors DIPF and ebelactone B. When DIPF and ebelactone B were applied to stigmas prior to pollination, pollen germination was not significantly affected but, at the highest inhibitor concentrations, up to 70% of germinating pollen tubes failed to penetrate the stigma surface. These data demonstrate that serine esterases, most probably cutinase(s), are required for pollen tube penetration of the dry cuticularised Brassica stigma.     

城市花粉致敏植物种类构成、分布与潜在危害评估——以深圳市为例

气传致敏花粉会引发过敏症,且可通过每年在花粉季的反复接触逐渐加重,危害人体健康,严重时甚至危害生命。花粉致敏植物在城市中被广泛引种栽培,导致城市花粉症患者数量激增。以深圳市为案例,基于建成区600个样地的实地调查数据,分析花粉致敏植物的种类构成与时空分布,通过构建花粉浓度及花粉致敏危害潜力计算公式,评估花粉致敏危害潜力及其分布特点。结果显示：①调查记录到深圳市建成区花粉致敏植物46科92属186种,其中外来种占43.37%,其中美洲、亚洲和大洋洲来源占国外外来种的81.00%。花粉致敏植物种数以公园绿地最多,达126种。植物花粉致敏等级以Ⅰ级为主,达154种。②花粉致敏植物的盛花期为春夏季,占全年累计开花种数的65.02%。最高峰出现在8月,开花种数达92种。 ③花粉浓度潜力最高值也出现在8月,占全年总值的12.13%。豆科和禾本科植物贡献比例较大,分别占乔木和草本总值的40.86%和64.13%。龙岗区花粉浓度潜力占比较高,占各季花粉量的26.06%-29.42%。④冬春两季各样地花粉致敏危害等级均不高,但夏秋季有些样地达到二级重度危害。罗湖区调查样地全年花粉致敏危害等级均较低,光明区在春夏秋季致敏危害等级皆较高。高危害等级样地主要出现在附属绿地及公园绿地。⑤花粉致敏植物防控措施情景模拟结果,去除主要花粉致敏植物种类比降低所有花粉致敏植物的花粉浓度潜力更有效。本研究为城市花粉致敏植物的管理、规划、养护和研究提供参考。     

Arabidopsis shaker pollen inward K~+ channel SPIK functions in SnRK1 complex-regulated pollen hydration on the stigma

Pollen hydration is a critical step that determines pollen germination on the stigma. KINβγ is a plantspecific subunit of the SNF1-related protein kinase 1 complex(SnRK1 complex). In pollen of the Arabidopsis kinbg mutant, the levels of reactive oxygen species were decreased which lead to compromised hydration of the mutant pollen on the stigma. In this study, we analyzed gene expression in kinβγ mutant pollen by RNA-seq and found the expression of inward shaker K~+ channel SPIK was down-regulated in the kinβγ pollen. Furthermore, we showed that the pollen hydration of the Arabidopsis spik mutant was defective on the wild-type stigma, although the mutant pollen demonstrated normal hydration in vitro.Additionally, the defective hydration of spik mutant pollen could not be rescued by the wild-type pollen on the stigma,indicating that the spik mutation deprived the capability of pollen absorption on the stigma. Our results suggest that the Arabidopsis SnRK1 complex regulates SPIK expression,which functions in determining pollen hydration on the stigma.     

A comparative analysis of distribution of glyprolines administered by various routes

The distribution of the glyprolines Pro-Gly-Pro and Thr-Lys-Pro-Arg-Pro-Gly-Pro (Selanc) was analyzed and compared in tissues of rat organs after different ways of their administration using the peptides uniformly labeled with tritium. Comparative data on changes in concentrations of the peptides in the rat organs after their intraperitoneal, intranasal, intragastric, and intravenous administration are given. The intranasal administration of both peptides was shown to be optimal for the delivery of glyproline molecules in the CNS. A high affinity of the studied glyprolines for gastric tissues was found for all the ways of their administration. We suggest that a high efficiency of action of glyprolines on homeostasis of the gastric mucous tunic was partially provided by accumulation of these peptides (to high concentrations) in gastric tissues.