Pollination and stigma wounding: same response, different signal?

In Petunia hybrida flowers, both pollination and stigma woundinginduced a transient Increase in ethylene production and hastenedcorolla senescence. Ethylene production by different flowerparts was measured in situ using laser photoacoustic (LPA) spectroscopy.In pollinated flowers, ethylene was exclusively produced bythe stigma/style region whereas wounding of the stigma Inducedethylene production both by the stigma/style region and by theremaining flower parts. In aminoethoxyvinylglycine (AVG)-treatedflowers, subsequent treatment of the unwounded stigma with 1-aminocyclopropane-1-carboxylicacid (ACC) induced ethylene production exclusively by the stigma/styleregion whereas treatment of a previously wounded stigma withACC induced a simultaneous increase in ethylene production bythe stigma/style region and the remaining flower parts. Theseresults suggest that following stigma wounding, either ACC orethylene is involved in inter-organ communication. Followingpollination, the signal is apparently not directly related toethylene. In vivo ACC oxidase activity of most flower parts, includingthe gynoecium, was higher in light than in dark. Light or darkdid not influence the relative contributions of stigma/styleand remaining flower parts to the total pollination, woundingor ACC-induced ethylene production, indicating that ACC is nottranslocated. Both in excised styles and intact flowers, radiolabelledACC and its analogue -aminoisobutyric acid (AIB), applied eitherto an intact or wounded stigma, were largely immobile confirmingthat ACC is not likely to play a role in inter-organ signalling. The results collectively suggest that following stigma wounding,translocation of ethylene may be the signal responsible forinitiation of corolla senescence; following pollination thesignal is not directly related to ethylene. Key words: 1-Aminocyclopropane-1-carboxylic acid (ACC), ethylene, flower senescence, Petunia hybrida, pollination, stigma wounding     

Structural analysis of stigma development in relation with pollen–stigma interaction in sunflower

Structural analysis of stigma development in sunflower highlights the secretory role of papillae due to its semi-dry nature. Production of lipid-rich secretions is initiated at the staminate stage of the flowers in stigma development and increases at the receptive stage, coinciding with an extensive development of elaioplasts and endoplasmic reticulum network in the basal region of the papillae. Transfer cells, earlier identified only in the wet type of stigma, are also present in the transmitting tissue of the sunflower stigma. Attainment of physiological maturity by the stigmatic tissue, accompanying development from bud to pistillate stage, appears to affect the initial steps of pollen–stigma interaction. The nature of self-incompatibility in Helianthus has also been investigated in relation with pollen adhesion, hydration and germination. Pollen adhesion to the stigma is a rapid process in sunflower and stigma papillae exhibit greater affinity for pollen during cross pollination as compared to self-pollination. Components of the pollen coat and the pellicle on the surface of stigmatic papillae are critical for the initial phase of pollen–stigma interaction (adhesion and hydration). The lipidic components of pollen coat and the proteinaceous and lipidic components from the surface of the papillae coalesce during adhesion, leading to the movement of water from stigma to the pollen, thereby causing pollen hydration and its subsequent germination. Pollen germination (both in self-and cross-pollen) on the stigma surface and the growth of the pollen tube characterize the flexibility of self-incompatibility in sunflower. Compatible pollen grains germinate and the pollen tube penetrates the stigma surface to enter the nutrient-rich transmitting tissue. The pollen tube from incompatible pollen germination, however, fails to penetrate the stigmatic tissue and it grows parallel to the papillae. Present findings provide new insights into structural and functional relationships during stigma development and pollen–stigma interaction.     

Does being Roma matter? Ethnic boundaries and stigma spillover in musical consumption

Manele songs, an updated version of traditional Romani music, are excluded from mainstream Romanian media due to their association with the country’s large Roma minority. The genre is at the intersection between Romania’s democratic transition and growing efforts to strengthen boundaries between the country’s marginalized Romani minority and the non-Romani majority population. But we find that media discussions around manele underscore a fluid relationship between ethnic boundaries and stigmatized cultural consumption. All those who listen to manele are portrayed in negative terms by the media, no matter whether ethnic markers are used as part of the portrayal. In the context of manele, genre-based stereotypes extend beyond ethnic boundaries to assign negative social value to a wide swathe of people who consume the genre. The stigma spillover surrounding manele audiences therefore underlines the ways in which Roma identity is fluid, and anyone associated with the Roma can be relegated to the lower rungs of social status. Manele show how the political process of ethnic boundary-making draws a wide net over those located at the bottom of power hierarchies.     

Getting respect or getting along with stigma?

By paying attention to the apparently minor forms of stigmatization, Getting Respect uncovers an underworld of threats that contribute to shape the sense of being disqualified and enlarge our understanding of racism and discrimination. In this paper, I engage with the main findings and argument of the book, especially the comparative dimension, questioning the status of the Israeli component of it. How “assaults on worth” that are key in this book are related to discrimination remain to be disentangled. One open question after reading this great research is whether we are facing a reformation of racism, with the new public debate on microaggression being both a symptom and a parameter of this evolution, or the book is a contribution to a deeper understanding of the expression of stigmatization in the same context of “racism without race” or “Laissez faire racism”.     

Racial boundaries,stigma, and the re-emergence of “always being foreigners”: Iranians and the refugee crisis in Germany

The 2015 refugee crisis is at the center of public and political discourse across Europe, especially among nations that have accepted refugees. Utilizing ethnographic fieldwork and 48 in-depth interviews conducted in 2011 and 2016 with Iranians in Hamburg, Germany, this paper considers how the refugee crisis impacts the racial boundaries between Germans and immigrant communities. It details how the crisis has made ethnic nationalism, Islamophobia, anti-foreigner prejudice and racism more pronounced and salient throughout Germany. The interviews demonstrate that this climate affects Iranians in several ways: they cite feeling more threat and stigma, as well as experiences of marginality, perpetual foreignness, and discrimination. This research contributes to sociological scholarship on migration and race by examining how critical international events influence and shape processes of racialization, identity and belonging, and social boundaries and hierarchies.     

β-1,3-glucanase activity in the stigma of healthy petunia flowers

β-1,3-Glucanase activity was detected in extracts of different tissues of healthy mature petunia flowers except the filament. The stigma was studied further as it had the highest enzyme activity and there is a paucity of information on the occurrence of this enzyme in this tissue. Specific activity of the enzyme was found to increase within the stigmatic tissue from early development until just before anthesis. Following non-denaturing polyacrylamide gel electrophoresis at pH 8.8, extracts of dehiscent stigma seem to contain three acidic isoforms of β-1,3-glucanase. Crude extracts of stigma was passed through a pachyman affinity column. A fraction of affinity-purified active β-1,3-glucanase enzyme was found to have no antifungal activity against Trichoderma viride, Phloma clematidina and Cladosporium fulvum.     

Large pollen at high temperature: an adaptation to increased competition on the stigma?

Pollen availability is a major constraint of plant reproductive success. Because pollen size trades-off with the quantity of produced grains, the link between climate characteristics and the determination of pollen size is of fundamental importance. To minimize the rate of water loss due to desiccation, a plant should produce larger grains that also have a lower surface-to-volume ratio. We used a comparative analysis to examine the hypothesis predicting increase in pollen size as a response to desiccation intensity. To test the hypothesis, we correlated the data on pollen size with the climate characteristics, temperature and desiccation intensity of the flowering period, for 232 plant species of 11 taxonomic groups. The analysis showed a positive relationship between the pollen size and temperature, but not with the desiccation intensity. We discuss the potential mechanisms by which increased temperature is an indicator of high competition among pollen grains on the stigma, which in turn is expected to promote large pollen. Our work provides insight into the temperature dependence of pollen production in plants and reveals a link between environmental temperature and the intensity of limitation of plant reproductive success by pollen availability. The result is relevant in the context of global climate change. We also discuss why environmental temperature has to be controlled in studies dealing with pollen production, particularly in investigations of size-number trade-off.     

White cruelty or Republican sins? Competing frames of stigma reversal in French commemorations of slavery

Abstract

This paper explores how French activists use claims about the history and legacies of slavery to combat stigmas associated with their group membership. Using a case study of a French Caribbean association (CM98) and a pan-African association (COFFAD), I examine how two organizations produce competing models for challenging and reversing the stigma of slavery. Through a process of normative inversion, activists assert the moral inferiority of dominant groups. CM98 rejects both a racial and an African identity, and seeks recognition for ‘French descendants of slaves’, using the language of citizenship to criticize the French government. COFFAD, by contrast, asserts an Afro-centric black identity and stigmatizes white Europeans. I argue that both destigmatization strategies unwittingly reinforce the stigma of historical enslavement.     

Does stigma curvature promote delayed selfing? An experimental investigation in Triodanis perfoliata (Campanulaceae)

• Self‐fertilisation that is delayed until after opportunities for outcrossing have ceased has been argued to provide both the reproductive assurance benefits of selfing and the genetic advantages of outcrossing. In the Campanulaceae, presentation of pollen on stylar hairs and progressive stigma curvature have been hypothesised to facilitate delayed selfing, but experimental tests are lacking. Stigma curvature is common in Campanula, a genus largely characterised by self‐incompatibility, and therefore is unlikely to have initially evolved to promote self‐fertilisation. In derived self‐compatible species, however, stigma curvature might serve the secondary function of delayed selfing.
• We investigated delayed selfing in Triodanis perfoliata, a self‐compatible relative of Campanula. Using floral manipulation experiments and pollen tube observations, we quantified the extent and timing of self‐pollination. Further, we hypothesised that, if stigma curvature provides the benefit of delayed selfing in Triodanis, selection should have favoured retention of self‐pollen through the loss of a stylar hair retraction mechanism.
• Results of a stigma removal experiment indicated that autonomous selfing produces partial seed set, but only some selfing was delayed. Pollen tube observations and a flower senescence assay also supported the finding of partial delayed selfing. Scanning electron microscopy revealed that pollen‐collecting hairs retract during anthesis, which may limit the extent of delayed selfing.
• Delayed selfing appeared to be only partially effective in T. perfoliata. The stylar hair retraction in this species would seem to contradict selection for selfing. We suggest that caution and rigour are needed in interpreting floral traits as adaptive mechanisms for delayed selfing.

     

Pollen donor identity affects timing of stigma receptivity in Collinsia heterophylla (Plantaginaceae): a sexual conflict during pollen competition?

Theory predicts that, during pollen competition, selection may favor a pollen trait that increases donor competitive ability at the expense of the female reproductive function. One such pollen trait could be manipulation of the onset of stigma receptivity. We evaluated the potential occurrence of this kind of sexual conflict by testing female control of the timing of stigma receptivity in the self-compatible annual Collinsia heterophylla. By performing one-donor crosses in the greenhouse, we found that differences in both recipients and pollen donors influenced when stigmas became receptive. Because we did not detect an interaction effect, our result suggests that some donors were consistently better than others at germinating pollen and siring seeds earlier. Unexpectedly, self-pollen was able to fertilize seeds earlier during floral development compared with outcross pollen. These results suggest that female control on timing of stigma receptivity is not complete in this species. In addition, fertilizations that occurred early during floral development resulted in fewer seeds than later fertilizations, possibly indicating a cost of lost control over the onset of receptivity. The ability of pollen donors to influence the timing of stigma receptivity might reflect a conflict between the sexual functions in C. heterophylla.     

Syntheses and spectroscopic properties of α- and β-phosphatidylcholines and phosphatidylethanolamines

The widely used partial synthesis of phospholipids via deacylation of naturally occurring phospholipids, followed by reacylation with fatty acid anhydrides, is accompanied by phosphoryl migration. The resulting mixture of α- and β-phospholipids was separated by short-column chromatography. Milder acylation procedures in which no phosphoryl migration occurs, were developed. 1,2-Dilinoleoyl-sn-glycero-3-phosphocholine was prepared in 50% yield by acylation of sn-glycero-3-phosphocholine (GPC) with N-linoleoylimidazole. Detailed NMR and infrared spectra of α- and β-phosphatidylcholines (PCs) and -ethanolamines (PEs) are reported and the differences between isomers discussed.     

Phenotypic plasticity and longevity in plants and animals: cause and effect?

Immobile plants and immobile modular animals outlive unitary animals. This paper discusses competing but not necessarily mutually exclusive theories to explain this extreme longevity, especially from the perspective of phenotypic plasticity. Stem cell immortality, vascular autonomy, and epicormic branching are some important features of the phenotypic plasticity of plants that contribute to their longevity. Monocarpy versus polycarpy can also influence the kind of senescent processes experienced by plants. How density-dependent phenomena affecting the establishment of juveniles in these immobile organisms can influence the evolution of senescence, and consequently longevity, is reviewed and discussed. Whether climate change scenarios will favour long-lived or short-lived organisms, with their attendant levels of plasticity, is also presented.     

Veneers and plywood—their manufacture and use

Two closely related industries that depend, to a major degree, upon domestic sources of red gum, Douglasfir, black walnut, red and white oaks, sugar maple, Sitka spruce, Ponderosa pine and Port Orford cedar; and upon foreign sources of mahogany, rosewood, zebrawood, avodiré, bossé, ebony and other exotic species.     

Dogmatisms and Catechisms — Ethics and Companion Animals

Abstract

The current reconsideration of the place in nature of human beings unfortunately continues to be an acrimonious one. All too often the debate is more akin to a warlike encounter where each side attempts to gain control or the upper hand than a search for points of agreement. Given this context, it is important to entertain views that emanate from different cultural traditions as a way to infuse the debate with new life. Students of Native American culture have consistently pointed out that the essential concepts of life balance and reciprocity represented there may serve as useful points of consideration as we struggle with the appropriate relationships with animals and nature. This article presents a representative Zuni story, told by Governor Robert E. Lewis, that illustrates these notions.     

DCCP and DICP： Construction and Analyses of Databases for Copper- and Iron-Chelating Proteins

Copper and iron play important roles in a variety of biological processes, especially when being chelated with proteins. The proteins involved in the metal binding, transporting and metabolism have aroused much interest. To facilitate the study on this topic, we constructed two databases （DCCP and DICP） containing the known copper- and iron-chelating proteins~ which are freely available from the website http：//sdbi.sdut.edu.cn/en. Users can conveniently search and browse all of the entries in the databases. Based on the two databases, bioinformatic analyses were performed, which provided some novel insights into metalloproteins.     

Biosynthesis of geraniol and nerol and their β-d-glucosides in Perlargonium graveolens and Rosa dilecta

1. 3R-[2-(14)C]Mevalonate was incorporated into geranyl and neryl beta-d-glucosides in petals of Rosa dilecta in up to 10.6% yield, and the terpenoid part was specifically and equivalently labelled in the moieties derived from isopentenyl pyrophosphate and 3,3-dimethylallyl pyrophosphate. A similar labelling pattern, with incorporations of 0.06-0.1% was found for geraniol or nerol formed in leaves of Pelargonium graveolens The former results provide the best available evidence for the mevalonoid route to regular monoterpenes in higher plants. 2. Incorporation studies with 3RS-[2-(14)C,(4R)-4-(3)H(1)]-mevalonate and its (4S)-isomer showed that the pro-4R hydrogen atom of the precursor was retained and the pro-4S hydrogen atom was eliminated in both alcohols and both glucosides. These results suggest that the correlation of retention of the pro-4S hydrogen atom of mevalonate with formation of a cis-substituted double bond, such as has been found in certain higher terpenoids, does not apply to the biosynthesis of monoterpenes. It is proposed that either nerol is derived from isomerization of geraniol or the two alcohols are directly formed by different prenyltransferases. Possible mechanisms for these processes are discussed. 3. The experiments with [(14)C,(3)H]mevalonate also show that in these higher plants, as has been previously found in animal tissue and yeast, the pro-4S hydrogen atom of mevalonate was lost in the conversion of isopentenyl pyrophosphate into 3,3-dimethylallyl pyrophosphate.     

Zinc and diabetes — clinical links and molecular mechanisms

Zinc is an essential trace element crucial for the function of more than 300 enzymes and it is important for cellular processes like cell division and apoptosis. Hence, the concentration of zinc in the human body is tightly regulated and disturbances of zinc homeostasis have been associated with several diseases including diabetes mellitus, a disease characterized by high blood glucose concentrations as a consequence of decreased secretion or action of insulin. Zinc supplementation of animals and humans has been shown to ameliorate glycemic control in type 1 and 2 diabetes, the two major forms of diabetes mellitus, but the underlying molecular mechanisms have only slowly been elucidated. Zinc seems to exert insulin-like effects by supporting the signal transduction of insulin and by reducing the production of cytokines, which lead to beta-cell death during the inflammatory process in the pancreas in the course of the disease. Furthermore, zinc might play a role in the development of diabetes, since genetic polymorphisms in the gene of zinc transporter 8 and in metallothionein (MT)-encoding genes could be demonstrated to be associated with type 2 diabetes mellitus. The fact that antibodies against this zinc transporter have been detected in type 1 diabetic patients offers new diagnostic possibilities. This article reviews the influence of zinc on the diabetic state including the molecular mechanisms, the role of the zinc transporter 8 and MT for diabetes development and the resulting diagnostic and therapeutic options.