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At least 109 records · Page 6Linked to original sources
PubMed1999

Identification of a pollen-specific sucrose transporter-like protein NtSUT3 from tobacco.

Pollen cells are symplasmically isolated during maturation and germination. Pollen therefore needs to take up nutrients via membrane carriers. Physiological measurements on pollen indicate sucrose transport in the pollen tube. A cDNA encoding a pollen-specific sucrose transporter-like protein NtSUT3 was isolated from a tobacco pollen cDNA library. NtSUT3 expression is detected only in pollen and is restricted to late pollen development, pollen germination and pollen tube growth. Altogether these data indicate that pollen is supplied not only with glucose, but also with sucrose through a specific sucrose transporter. The respective contribution of each transport pathway may change during pollen tube growth.

Amino Acid Sequence↗
PubMed1997

Cloning and characterization of a pollen-specific cDNA encoding a glutamic-acid-rich protein (GARP) from potato Solanum berthaultii.

A pollen-specific cDNA was isolated from a cDNA library of in vitro germinated pollen of the diploid potato species Solanum berthaultii. The cDNA clone, designated SB401, hybridizes to a messenger RNA of 1.2 kb length in mature and germinated pollen. SB401 messenger RNA is absent from other parts of the plant, including other flower tissues. SB401 cDNA, which possesses a long stretch of AT-rich 5'-untranslated leader sequence, encodes a glutamic acid-rich protein (GARP) which is hydrophilic throughout and contains six imperfect repeated motifs of the sequence V-V-E-K-K-N/E-E with the di-basic amino acid residue pair (K-K) as the core within the repeats. These repeats are spaced at irregular intervals and predicted to form an alpha-helical structure. The SB401 protein was over-expressed in Escherichia coli and the purified protein was used for raising antiserum. Both E. coli-expressed and the endogenous SB401 proteins in pollen and pollen tubes appear much larger on SDS-polyacrylamide gels than their calculated molecular masses. Immunoblotting revealed the protein to be most abundant in germinated pollen. The structural features of SB401 protein and a possible role for the protein in pollen development, pollen germination, and pollen tube growth are discussed.

Amino Acid Sequence↗
PubMed1988

Desiccation Tolerance of Papaver dubium L. Pollen during Its Development in the Anther: Possible Role of Phospholipid Composition and Sucrose Content.

Developing pollen of Papaver dubium L. becomes functional and desiccation tolerant at approximately 2 to 1 days prior to anthesis, coincident with degradation of starch and a doubling of the amount of sucrose, the primary soluble carbohydrate present. When anthers were taken from flower buds at 3 days before anthesis, pollen dehisced upon exposure to the ambient air. This dried pollen did not fluoresce with the vital stain fluorescein diacetate, had increased leakage of K(+), and did not swell properly in a germination medium. In contrast, pollen became functional and desiccation resistant when these young anthers were first incubated in a water-saturated atmosphere for 30 hours. Phospholipid composition revealed no major differences over the last 3 days of development. When this immature pollen was liberated mechanically and allowed to mature in humid air, starch degraded and sucrose content nearly doubled, and the grains became largely functional and dehydration tolerant. Large unilamellar vesicles were prepared from isolated phospholipids to study dehydration-induced fusion and leakage. When dried in the presence of increasing concentrations of sucrose, vesicle integrity was progressively retained. These data indicate that pollen maturation during the last 3 days of development occurred independently from the parent plant. Sucrose may play an essential role in the acquired tolerance to severe dehydration.

Journal Article↗
PubMed1997

Regulation of flavonol biosynthesis during anther and pistil development, and during pollen tube growth in Solanum tuberosum.

The regulation of flavonol biosynthesis was studied in anthers and pistils of Solanum tuberosum. Flavonols are essential for functional pollen tube growth in a number of species. Flavonol accumulation in whole anthers started at the unicellular stage of pollen development and continued until pollen maturity. A cDNA clone encoding flavonol synthase (FLS) was isolated. Fls gene expression was detected in pistils, anthers, petals and ovaries, the organs in which flavonols are accumulating. Fls transcripts were present in unicellular and bicellular pollen, but not in mature pollen. The expression patterns of three genes encoding enzymes in the flavonoid biosynthetic pathway, chalcone synthase (chs), flavanone-3-hydroxylase and fls were analysed in developing anthers and pistils. Only chs transcripts accumulated concomitantly with the flavonols in anthers. In pistils of potato, pollen tube growth induced an increase in fls gene expression that, unlike the situation in pollinated pistils of petunia, did not result in an increased flavonol content. Flavonol biosynthesis in anthers is probably initiated by the expression of the chs gene, and flavonol accumulation in pistils upon pollen tube growth is not an universal phenomenon.

Acyltransferases↗
PubMed2006

Protein phosphatases 1 and 2A and the regulation of calcium uptake and pollen tube development in Picea wilsonii.

To investigate the roles of protein phosphatases 1 and 2A in the development of pollen tubes of Picea wilsonii Mast., pollen grains were cultured in standard medium in the presence and absence of the protein phosphatase inhibitors okadaic acid and calyculin A. At nanomolar concentrations, these compounds blocked pollen tube growth, causing abnormal morphologies of the pollen tubes. Studies with Fluo-3 revealed that the inhibitors reduced the pollen-tube tip-to-base cytoplasmic calcium (Ca(2+)) gradient and arrested extracellular Ca(2+) uptake. The transmission electron microscope observations indicated that the fusion of paramural bodies with plasma membranes occurred frequently in the tip and sub-tip regions of control pollen tubes, but fusion rarely occurred in inhibitor-treated pollen tubes. Staining with aniline blue showed that callose accumulated in the tip regions of inhibitor-treated pollen tubes. Immunolabeling of pollen tubes revealed that acidic pectin epitopes recognized by the monoclonal antibody JIM5 were present in the tip region and on the flanks of the sub-tip in normal pollen tubes. In inhibitor-treated pollen tubes, these epitopes existed only in the extreme tip region and at higher concentrations than in control pollen tubes. The esterified pectin recognized by JIM7 was located preferentially at the extreme tip region in normal pollen tubes, but at basal sites in inhibitor-treated tubes. Fourier transform infrared (FTIR) analysis further confirmed the changes in acidic and esterified pectin distributions and their relative contents. These results suggest that protein phosphatase 1 or 2A, or both, are involved in the regulation of Ca(2+) uptake across the plasma membrane, in exocytotic activity and in the biosynthesis of cell wall components, all processes that occur in the tip region of pollen tubes and that control pollen tube development.

Biological Transport↗
PubMed1999

Localization of the Ca(2+)-binding protein, Bra r 1, in anthers and pollen tubes.

Calcium plays an essential role during pollen development and pollen tube growth, and several Ca(2+)-binding proteins are expressed in anthers. We have previously reported that Brassica pollen allergens encoded by Bra r 1 and Bra r 2 show sequence similarities to Ca(2+)-binding proteins [Toriyama et al. (1995) Plant Mol. Biol. 29: 1157]. Herein, we report that both genes are expressed in the diploid tapetum and haploid microspores, as detected by in situ RNA hybridization. Immunoblot analysis revealed that Bra r 1 and Bra r 2 were accumulated in anthers during pollen development. When pollen grains were suspended in an aqueous solution, both proteins were mainly detected in the pollen extracellular fraction, indicating that Bra r 1 and Bra r 2 are released from the pollen upon hydration. Localization of Bra r 1 was further investigated in sections of anthers and pollen tubes. Bra r 1 was detected in the tapetum, microspores and pollen grains. In longitudinal sections of cross-pollinated pistils. Bra r 1 was detected throughout pollen tubes elongating in transmitting-tissue. These findings suggest that Bra r 1 may be involved in pollen-pistil interaction and pollen tube growth.

Allergens↗
PubMed1994

Hsp70 heat shock protein cognate is expressed and stored in developing tomato pollen.

Pollen of angiosperms lacks the ability to respond to heat stress by synthesizing heat shock proteins (hsps). In tomato developing microspores were found to have 70 kDa heat shock proteins (hsp70s) present throughout development, even in the absence of heat stress. Heat shock protein family members expressed in the absence of heat stress are called cognate (hsc70) genes. Antisense RNA and antibody probes were used for in situ hybridizations which detected hsc70 expression in developing pollen of immature buds. Hsc70 mRNA transcripts and proteins were detected in nonstressed sporogenous tissues, microspores and in pre-tapetal layers during early pollen development. While immunoblot analysis detected hsc70 proteins stored in mature pollen, heat stress could not induce the synthesis of new hsp70 protein as measured by 35S-methionine labeling followed by immunoprecipitation.

HSP70 Heat-Shock Proteins↗
PubMed2002

[Aberrant development of pollen in transgenic tobacco expressing bacterial iaaM gene driven by pollen- and tapetum-specific promoters].

Microsporogenesis offers an ideal model for studying gene expression, cell division and cell to cell communication during development. The role of auxin in pollen development was investigated in transgenic tobacco plants expressing the coding region of the iaaM gene from Pseudomonas syringae, under control of the promoters Lat-52 (pollen-specific) or TA-29 (tapetum-specific). IAA level in anther of transgenic plants increased significantly, and transgenic plants displayed morphological aberrations not solely attributable to pollen development(such as adventitious root formation on stems, epinastic leaf growth, delayed flowering). These results suggest that expression of Lat-52 and TA-29 are not strictly limited to anther. Anther shape was changed and the number of pollen grains per anther was reduced, but grains could be stained with aceto-carmine. Almost all flowering plants were fertile, although the number of flowers per inflorescence was reduced compared with the wild-type ones. These results suggest that auxin plays an important role in pollen development, and over-expressing auxin synthesis gene could result in aberrant development of pollen.

Bacterial Proteins↗
PubMed2005

Molecular genetic analyses of microsporogenesis and microgametogenesis in flowering plants.

In flowering plants, male reproductive development requires the formation of the stamen, including the differentiation of anther tissues. Within the anther, male meiosis produces microspores, which further develop into pollen grains, relying on both sporophytic and gametophytic gene functions. The mature pollen is released when the anther dehisces, allowing pollination to occur. Molecular studies have identified a large number of genes that are expressed during stamen and pollen development. Genetic analyses have demonstrated the function of some of these genes in specifying stamen identity, regulating anther cell division and differentiation, controlling male meiosis, supporting pollen development, and promoting anther dehiscence. These genes encode a variety of proteins, including transcriptional regulators, signal transduction proteins, regulators of protein degradation, and enzymes for the biosynthesis of hormones. Although much has been learned in recent decades, much more awaits to be discovered and understood; the future of the study of plant male reproduction remains bright and exciting with the ever-growing tool kits and rapidly expanding information and resources for gene function studies.

Cell Differentiation↗
PubMed2006

[Preliminary proteomics analysis of the total proteins of HL Type cytoplasmic male sterility rice anther].

The proteins of HL type cytoplasmic male sterility rice anther of YTA (CMS) and YTB (maintenance line) were separated by two-dimensional electrophoresis with immobilized ph (3-10 non-linear) gradients as the first dimension and SDS-PAGE as the second. The silver-stained proteins spots were analyzed using Image Master 2D software, there were about 1800 detectable spots on each 2D-gel, and about 85 spots were differential expressed. With direct MALDI-TOF mass spectrometry analysis and protein database searching, 9 protein spots out of 16 were identified. Among those proteins, there were Putative nucleic acid binding protein, glucose-1-phosphate adenylyltransferase (ADP-glucose pyrophosphorylase, AGPase) (EC: 2.7.7.27) large chain, UDP-glucuronic acid decarboxylase, putative calcium-binding protein annexin, putative acetyl-CoA synthetase and putative lipoamide dehydrogenase etc. They were closely associated with metabolism, protein biosynthesis, transcription, signal transduction and so on, all of which are cell activities that are essential to pollen development. Some of the identified proteins, i.e. AGPase, putative lipoamide dehydrogenase and putative acetyl-CoA synthetase were deeply discussed on the relationship to CMS. AGPase catalyzes a very important step in the biosynthesis of alpha 1,4-glucans (glycogen or starch) in bacteria and plants: synthesis of the activated glucosyl donor, ADP-glucose, from glucose-1-phosphate and ATP. The lack of the AGPase in male sterile line might directly result in the reduction of starch, and the synthesis of starch was the most important processes during the development of pollen. In present research, the descent or reduction of putative lipoamide dehydrogenase and putative acetyl-CoA synthetase seemed involved in pollen sterility in rice. The degeneration and formation of various tissues during pollen development may impose high demands for energy and key biosynthetic intermediates. Under such conditions, the TCA cycle needs to operate fully, because the TCA cycle is an important source for many intermediates required for biosynthetic pathways, in addition to performing an oxidative, energy-producing role. Thus, it seemed reasonable to infer that the decrease of putative lipoamide dehydrogenase and putative acetyl-CoA synthetase in anther might prevent the conversion of pyruvate into acetyl-CoA, and as a result, the TCA cycle could no longer operate at a sufficient rate to meet all requirements in anther cells, leading to pollen sterility. This study gave new insights into the mechanism of CMS in rice and demonstrated the power of the proteomic approach in plant biology studies.

Electrophoresis, Polyacrylamide Gel↗
PubMed2003

A calmodulin-binding protein from Arabidopsis has an essential role in pollen germination.

Calmodulin (CaM), a ubiquitous multifunctional calcium sensor in all eukaryotes, mediates calcium action by regulating the activity/function of many unrelated proteins. Although calcium and CaM are known to play a crucial role in pollen germination and pollen tube growth, the proteins that mediate their action have not been identified. We isolated three closely related CaM-binding proteins (NPG1, NPGR1, and NPGR2) from Arabidopsis. NPG1 (No Pollen Germination1) is expressed only in pollen, whereas the NPG-related proteins (NPGR1 and NPGR2) are expressed in pollen and other tissues. The bacterially expressed NPG1 bound three isoforms of Arabidopsis CaM in a calcium-dependent manner. To analyze the function of NPG1, we performed a reverse genetics screen and isolated a mutant in which NPG1 is disrupted by a T-DNA insertion. Segregation and molecular analyses of the NPG1 knockout mutant and a cross with a male sterile mutant indicate that the mutated NPG1 is not transmitted through the male gametophyte. Expression of NPG1 in the knockout mutant complemented the mutant phenotype. Analysis of pollen development in the knockout mutant by light microscopy showed normal pollen development. Pollen from NPG1 mutant in the quartet background has confirmed that NPG1 is dispensable for pollen development. However, germination studies with pollen from the mutant in the quartet background indicate that pollen carrying a mutant allele does not germinate. Our genetic, histological, and pollen germination studies with the knockout mutant line indicate that NPG1 is not necessary for microsporogenesis and gametogenesis but is essential for pollen germination.

Alleles↗
PubMed2005

Dynamics of storage reserve deposition during Brassica rapa L. pollen and seed development in microgravity.

Pollen and seeds share a developmental sequence characterized by intense metabolic activity during reserve deposition before drying to a cryptobiotic form. Neither pollen nor seed development has been well studied in the absence of gravity, despite the importance of these structures in supporting future long-duration manned habitation away from Earth. Using immature seeds (3-15 d postpollination) of Brassica rapa L. cv. Astroplants produced on the STS-87 flight of the space shuttle Columbia, we compared the progress of storage reserve deposition in cotyledon cells during early stages of seed development. Brassica pollen development was studied in flowers produced on plants grown entirely in microgravity on the Mir space station and fixed while on orbit. Cytochemical localization of storage reserves showed differences in starch accumulation between spaceflight and ground control plants in interior layers of the developing seed coat as early as 9 d after pollination. At this age, the embryo is in the cotyledon elongation stage, and there are numerous starch grains in the cotyledon cells in both flight and ground control seeds. In the spaceflight seeds, starch was retained after this stage, while starch grains decreased in size in the ground control seeds. Large and well-developed protein bodies were observed in cotyledon cells of ground control seeds at 15 d postpollination, but their development was delayed in the seeds produced during spaceflight. Like the developing cotyledonary tissues, cells of the anther wall and filaments from the spaceflight plants contained numerous large starch grains, while these were rarely seen in the ground controls. The tapetum remained swollen and persisted to a later developmental stage in the spaceflight plants than in the ground controls, even though most pollen grains appeared normal. These developmental markers indicate that Brassica seeds and pollen produced in microgravity were physiologically younger than those produced in 1 g. We hypothesize that microgravity limits mixing of the gaseous microenvironments inside the closed tissues and that the resulting gas composition surrounding the seeds and pollen retards their development.

Brassica↗
PubMed1997

TETRASPORE is required for male meiotic cytokinesis in Arabidopsis thaliana.

In flowering plants, male meiosis occurs in the microsporocyte to produce four microspores, each of which develops into a pollen grain. Here we describe four mutant alleles of TETRASPORE (TES), a gene essential for microsporocyte cytokinesis in Arabidopsis thaliana. Following failure of male meiotic cytokinesis in tes mutants, all four microspore nuclei remain within the same cytoplasm, with some completing their developmental programmes to form functional pollen nuclei. Both of the mitotic divisions seen in normal pollen development take place in tes mutants, including the asymmetric division required for the differentiation of gametes; some tes grains perform multiple asymmetric divisions in the same cytoplasm. tes pollen shows a variety of abnormalities subsequent to the cytokinetic defect, including fusion of nuclei, formation of ectopic internal walls, and disruptions to external wall patterning. In addition, ovules fertilized by tes pollen often abort, possibly because of excess paternal genomes in the endosperm. Thus tes mutants not only reveal a gene specific to male meiosis, but aid investigation of a wide range of processes in pollen development and function.

Alleles↗
PubMed2002

Pollen tube development and competitive ability are impaired by disruption of a Shaker K(+) channel in Arabidopsis.

Sexual reproduction in plants requires elongation of the pollen tube through the transmitting tissues toward the ovary. Tube growth rate is a major determinant of pollen competitive ability. We report that a K(+) channel of the Shaker family in Arabidopsis, SPIK, plays an important role in pollen tube development. SPIK was found to be specifically expressed in pollen. When SPIK was heterologously expressed in COS cells, its product formed hyperpolarization-activated K(+) channels. Disruption (T-DNA insertion) of the SPIK coding sequence strongly affected inwardly rectifying K(+)-channel activity in the pollen-grain plasma membrane. Measurements of membrane potential in growing pollen tubes yielded data compatible with a contribution of SPIK to K(+) influx. In vitro pollen germination assays were performed, revealing that the disruption results in impaired pollen tube growth. Analysis of the transmission rate of the disrupted allele in the progeny of heterozygous plants revealed a decrease in pollen competitive ability, the probability of fertilization by mutant pollen being approximately 1.6 times lower than that by wild-type pollen. The whole set of data supports the hypothesis that functional expression of SPIK plays a role in K(+) uptake in the growing pollen tube, and thereby in tube development and pollen competitive ability.

Animals↗
PubMed2004

Selective expression of a novel high-affinity transport system for acidic and neutral amino acids in the tapetum cells of Arabidopsis flowers.

Within the flower, microsporogenesis represents a major sink for nitrogen, but knowledge on how the imported nitrogen is transferred from the anther cell layers to developing pollen is lacking. Here, we provide information on characterization of a transporter (AtLHT2) that might play an important role in partitioning of amino acids for microspore development. Biochemical analysis in yeast showed that AtLHT2 transports proline and aspartate with high affinity. However, other neutral and acidic amino acids act as strong competitors for proline and aspartate uptake indicating that AtLHT2 generally transports uncharged and negatively charged amino acids. Comparison of the apparent K(m) values of AtLHT2 with previously characterized amino acid transporters clearly demonstrated that AtLHT2 represents a novel high-affinity system for neutral and acidic amino acids. Northern blot analysis showed strong expression of the amino acid transporter in flower buds. Cellular expression could be resolved by using RNA in situ hybridization and in situ RT-PCR methods, which localized AtLHT2 specifically to the tapetum tissue of the anthers. Developing pollen grains are symplasmically isolated from the sporophytic tissue and rely on the nutrients and other compounds secreted from the tapetum cells. Thus, the functional characterization of AtLHT2, together with our expression and localization studies, strongly suggest that in Arabidopsis flowers, AtLHT2 has a critical function in import of neutral and acidic amino acids into the tapetum cells for synthesis of compounds important for microspore structure and in transfer of organic nitrogen to the locule for pollen development.

Amino Acid Transport Systems↗
PubMed1995

[An attempt of applying the image processing for the automatic estimation of sampled airborne pollen].

Development of techniques to rapidly and easily estimate an airborne pollen quantity is necessitated in order to make out a appropriate prescription for an allergy patient from medical clinical viewpoints, and in order to research a movement of allergen from medical basic viewpoint. The measurement of airborne pollen quantity required a large labour and time, because the amount of pollen grains is visually measured by naked eye. This paper, as a first step to estimate an airborne pollen quantity full-automatically, discuss techniques to measure the quantity of sampled airborne cedar pollen automatically and rapidly using the image processing techniques. As a result, the following facts are cleared. Automatic measurement is possible to some degree without any special image processing. It is important to eliminate a noise on image as blurs on basefilm for high accuracy measurement. The precision has improved fairly with level correction for image. Sharpening filter is the most appropriate process to improve the accuracy of automatic measurement of sampled airborne pollen. This filtering process has a merit that the operativeness is easy.

Air Pollutants↗