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Plant Systematics and Evolution, Vol. 222, No. 1. (1 March 2000), pp. 1-17.Qualities of the stratified pollen walls were evaluated for their possible role in pollination (pollination modes, and pollen tube formation). The importance of studying pollen grains in their respective natural state is noted. Examples of pollen morphological features specific to pollination vectors are rare and difficult to demonstrate. However, some complex, but significant correlations are reported.M Hesse, citeulike.org

Development (Cambridge, England), Vol. 126, No. 23. (December 1999), pp. 5431-5440.To investigate the nature and role of cell adhesion in plants, we analyzed the initial step of pollination in Arabidopsis: the binding of pollen grains to female stigma cells. Here we show this interaction occurs within seconds of pollination. Because it takes place prior to pollen hydration, it also requires adhesion molecules that can act in a virtually dry environment. We developed assays that monitored adhesion of populations of pollen grains and individual cells. Adhesion between pollen and stigma cells is highly selective - Arabidopsis pollen binds with high affinity to Arabidopsis stigmas, while pollen from other species fails to adhere. Initial binding is independent of the extracellular pollen coat (tryphine), indicating that adhesion molecules reside elsewhere on the pollen surface, most likely within the exine walls. Immediately after pollination, the stigma surface becomes altered at the interface, acquiring a pattern that interlocks with the exine; this pattern is evident only with pollen from Arabidopsis and its close relatives. Purified exine fragments bind to stigma cells, and biochemical analyses indicate that this specific, rapid and anhydrous adhesion event is mediated by lipophilic interactions.GM Zinkl, BI Zwiebel, DG Grier, D Preuss, citeulike.org

Metrologia (January 2002), pp. 531-534.The restrictions inherent in the use of the conventional reference in capillary viscometry, the viscosity of water at 20 °C, have led to increased interest in absolute viscometers. The viscosity laboratory of the Bureau National de Métrologie, Laboratoire National d"Essais (BNM-LNE) has begun the study of an absolute falling-ball viscometer. The principal difficulties with this system are the measurement of the velocity of the ball and the corrections to compensate for the effects exercised on the ball. Results from a preliminary experiment indicate that uncertainties better than those of capillary viscometers can be obtained. The use of a velocity measurement video system should further reduce the uncertainties.T Lommatzsch, M Megharfi, E Mahe, E Devin, citeulike.org

Journal of experimental botany, Vol. 54, No. 380. (January 2003), pp. 47-54.The mechanisms of compatible pollination are less studied than those of incompatible pollination and yet most of the angiosperms show self-compatibility. From the release of pollen from anthers to the penetration of the micropyle by the pollen tube tip, there are numerous steps where the interaction between pollen and the pistil can be regulated. Recent studies have documented some diverse ways in which pollen tubes carrying sperm cells are guided to the ovules through the pistil extracellular matrices of the transmitting tract. What is still missing is an understanding of pollen tube cell biology in vivo. A recent finding supports the role of the synergids in the crucial guidance cue for the pollen tube tip at the micropyle, but experimental evidence for other 'guidepost' cells in the pistil is still lacking. The fact that the pollen tube must first travel through the matrices of the stigma and style before it can respond to the cue from the ovule makes it likely that there is a hierarchy of signalling events in pollen-pistil interactions starting at the stigma and ending at the micropyle. On the pistil side, several model systems have been used in the discovery of molecules implicated in either physical or chemical guidance. In lily, which has a hollow style, adhesion molecules (pectin and SCA) are implicated in guidance. SCA alone is also capable of inducing pollen chemotropism in an in vitro assay, suggesting that this peptide plays a dual role in lily pollination: chemotactic in the stigma and haptotactic (adhesion mediated) in the style.EM Lord, citeulike.org

Journal of cell science, Vol. 66 (March 1984), pp. 255-264.Mature, self-incompatible stigmas exposed to cycloheximide for 2 h prior to pollination supported identical germination and growth of both cross and self pollen. Treatment of self-pollinated pistils with cycloheximide resulted in the germination of hitherto inactive pollen after some 2-4 h. Pollen germination and initial tube growth in an in vitro germination medium were not significantly affected by cycloheximide. A continuous synthesis of stigmatic proteins is therefore essential for the operation of the self-incompatibility (S.I.) system. However, light-microscope autoradiography of stigmas fed with L-leucine prior to pollination revealed no movement of stigmatic proteins into the pollen, independent of the compatibility of the pollen with respect to the stigma. Further, tunicamycin, when applied in the same way as cycloheximide, had no effect on the S.I. system. These results are discussed in terms of the proposed cycling of proteins in the papillar cell wall and the involvement of a stigmatic glycoprotein in the S.I. response.IN Roberts, G Harrod, HG Dickinson, citeulike.org

Sexual Plant Reproduction, Vol. 12, No. 5. (4 April 2000), pp. 302-309.Abstract?  Pollen coatings have long been assumed to play a pivotal role in pollen-stigma interactions, but until now little clear evidence supporting such a function has been available. Recently, however, the use of isolated coatings of Brassica sp. in experiments in vivo has unequivocally demonstrated that the pollen coat layer is responsible for activation of the stigmatic surface, and that it contains the male determinant of the self-incompatibility system. Surprisingly, molecular analysis of the Brassica pollen coat reveals this layer to include both sporophytic and gametophytic components, the latter including a family of small highly-charged proteins which interact with stigmatic molecules known to be encoded by the S(incompatibility)-locus. Most recently, work on Brassica and Arabidopsis suggests that the adhesive function of the coating is more complex than suspected and involves both stigmatic factors and the exine surface itself. Despite this new insight into the genetics and function of pollen coatings, the mechanisms by which components of these layers are formed in the tapetum and translocated to the pollen grain surface remain far from clear.HG Dickinson, CJ Elleman, J Doughty, citeulike.org

Chinese Science Bulletin, Vol. 53, No. 7. (23 April 2008), pp. 1015-1020.Abstract  During compatible pollination in tobacco, an extracellular matrix (ECM) is secreted from the stigma surface; however, it is unknown whether the pattern of secretion across the stigma depends on the pollen source. In fact, technical limitations have prevented clear observation of ECM secretion. Here, we report the detailed topographic changes on the stigma surface that accompanies intraspecies and interspecies pollination in tobacco using contact mode atomic force microscopy (AFM). Our results, which show the dynamics and time course of ECM secretion after pollination, indicate that a certain pattern of secretion already exists on the stigma prior to pollination. Intraspecies induced a two-step response, characterized by topographical changes on the stigma surface several hours after pollination, which was distinct from the pattern of ECM secretion induced by interspecies pollination. This difference was confirmed by root-mean-square analysis, which assessed the roughness of the stigma surface. Our findings indicate that compatible pollination not only induces ECM secretion from the stigma, but also results in a specific distribution of the ECM. Thus, this study demonstrates the powerful potential of AFM in studying the pollen-stigma interaction.Hui Wu, Meng Li, Mengxiang Sun, citeulike.org

Planta, Vol. 196, No. 2. (1995), pp. 367-374.Two S(self-incompatibility)-family glycoproteins have been identified in stigmas of self-compatible (SC) Brassica napus L. by their ability to interact, in vitro, with a peptide fraction from the pollen coating containing a PCP7-like peptide, PCP7 (pollen coat peptide 7) being a pollen coat peptide from self-incompatible (SI) Brassica oleracea L. which has been shown to interact with S-locus glycoproteins (SLGs). Electrophoretic purification and N-terminal amino-acid sequencing of these stigmatic glycoproteins confirmed one to be an SLG and the other to be a class 1 S-locus-related glycoprotein (SLR1). This is the first reported isolation of SLG and SLR1 proteins from SC B. napus and the first time that a PCP7-like peptide has been shown to interact with an S-class glycoprotein other than SLG. On the basis of these findings we suggest that an ability to interact with PCP7 or a PCP7-like peptide is a property of SLGs, SLR1s and possibly other S-glycoproteins and may thus provide a novel route to the identification of these glycoproteins in stigmatic extracts. The levels of the SLG in stigmas of SC B. napus were relatively much lower than the levels of the SLR1--the opposite to the situation in SI B. oleracea. This finding is discussed in terms of translational control of SLGs and SLR1, and the possible implications for self-incompatibility in B. oleracea and self-compatibility in B. napus.SJ Hiscock, J Doughty, AC Willis, HG Dickinson, citeulike.org

Plant Physiol, Vol. 138, No. 2. (June 2005), pp. 744-756.Upon germination, pollen forms a tube that elongates dramatically through female tissues to reach and fertilize ovules. While essential for the life cycle of higher plants, the genetic basis underlying most of the process is not well understood. We previously used a combination of flow cytometry sorting of viable hydrated pollen grains and GeneChip array analysis of one-third of the Arabidopsis (Arabidopsis thaliana) genome to define a first overview of the pollen transcriptome. We now extend that study to approximately 80% of the genome of Arabidopsis by using Affymetrix Arabidopsis ATH1 arrays and perform comparative analysis of gene family and gene ontology representation in the transcriptome of pollen and vegetative tissues. Pollen grains have a smaller and overall unique transcriptome (6,587 genes expressed) with greater proportions of selectively expressed (11%) and enriched (26%) genes than any vegetative tissue. Relative gene ontology category representations in pollen and vegetative tissues reveal a functional skew of the pollen transcriptome toward signaling, vesicle transport, and the cytoskeleton, suggestive of a commitment to germination and tube growth. Cell cycle analysis reveals an accumulation of G2/M-associated factors that may play a role in the first mitotic division of the zygote. Despite the relative underrepresentation of transcription-associated transcripts, nonclassical MADS box genes emerge as a class with putative unique roles in pollen. The singularity of gene expression control in mature pollen grains is further highlighted by the apparent absence of small RNA pathway components.C Pina, F Pinto, JA Feijó, JD Becker, citeulike.org

Nature, Vol. 413, No. 6855. (4 October 2001), pp. 534-538.Seiji Takayama, Hiroko Shimosato, Hiroshi Shiba, Miyuki Funato, Fang-Sik Che, Masao Watanabe, Megumi Iwano, Akira Isogai, citeulike.org