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Tandon Rajesh; Manohara T. N.; Nijalingappa B. H. M.; Shivanna K. R. 《Annals of botany》2001,87(6):831-838
Structural and cytochemical aspects of the pistil and detailsof pollination and pollen-pistil interaction were investigatedin the African oil palm (Elaeis guineensis Jacq.), an importantperennial oil crop. The stigma is trilobed, wet and papillate.The branched papillae are confined to a narrow linear zone oneach stigmatic lobe. Each stigmatic lobe harbours a deep stigmaticgroove, which runs adaxially along the surface. The stigmaticgroove is bordered by a well-defined layer of glandular cells,each of which has a pectinaceous cap on the inner tangentialwall. The style is hollow. The canal cells show thickeningson the inner tangential wall. The stigmatic groove and stylarcanal contain an extracellular matrix secreted by the canalcells which is rich in proteins, acidic polysaccharides andpectins. The canal cells at the base of the style are papillateand loosely fill the stylar canal. The stigma becomes receptivewhen the stigmatic lobes separate, and remains so for 24 h.Pollination is mediated by weevils as well as by the wind. Undernatural conditions the pollination efficiency was 100%. Pollinationinduces additional secretion in the stigmatic groove and stylarcanal. During post-pollination secretion, the pectinaceous capsof the cells lining the stigmatic groove are degraded. Pollengrains germinate on the stigmatic papillae and tubes grow onthe surface of the papillae, entering the stigmatic groove andadvancing along it into the stylar canal to eventually gainaccess to the locules. Pollen tubes are seen in the ovules 1820h after pollination. Copyright 2001 Annals of Botany Company Arecaceae, Elaeis guineensis, African oil palm, pollination, stigmatic grove, stylar canal, Tenera hybrid, weevil 相似文献
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Subplastidic preparations from cotyledons of cucumber (Cucumis sativus L.) were tested for their ability to synthesize protoporphyrin IX from the substrate 5-aminolevulinic acid. Envelope or thylakoid
membranes failed to synthesize protoporphyrin IX from the substrate 5-aminolevulinic acid. Stromal preparations synthesized
a very low amount of protoporphyrin IX. In a reconstitution experiment using stroma + envelope membranes, protoporphyrin IX
synthesis from 5-aminolevulinic acid was enhanced by 660% over that of stroma alone. However, when thylakoids were added to
the stroma + envelope mixture, protoporphyrin IX synthesis from 5-aminolevulinic acid was completely inhibited. In the reconstituted
stroma + envelope membrane mixture, the reducing agent dithiothreitol enhanced the protoporphyrin IX-synthesizing ability
and completely abolished the inhibition of protoporphyrin IX synthesis by thylakoids. This suggested that the oxidizing agents
usually associated with the thylakoid membranes inhibited protoporphyrin IX biosynthesis and the inhibition was alleviated
by the reducing power of dithiothreitol. This study exposes the weakness of in vitro reconstitution experiments in mimicking
the in vivo-conditions. Addition of ATP stimulated protoporphyrin IX synthesis by 50% in the supernatant fraction of chloroplast
lysate. This ATP-induced stimulation of protoporphyrin IX synthesis was due to the enhancement of the activities of uroporphyrinogen
decarboxylase and protoporphyrinogen oxidase, involved in tetrapyrrole biosynthesis. The ATP-induced stimulation of porphyrinogen
oxidase activity was an energy-dependent reaction.
Received: 21 March 2000 / Accepted: 9 May 2000 相似文献
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Processing of human cytomegalovirus UL37 mutant glycoproteins in the endoplasmic reticulum lumen prior to mitochondrial importation
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Mavinakere MS Williamson CD Goldmacher VS Colberg-Poley AM 《Journal of virology》2006,80(14):6771-6783
The human cytomegalovirus (HCMV) UL37 glycoprotein (gpUL37) is internally cleaved and its products divergently traffic to mitochondria or are retained in the secretory pathway. To define the requirements for gpUL37 cleavage, residues -1 and -3 of the consensus endoplasmic reticulum (ER) signal peptidase I site within exon 3 (UL37x3) were replaced by bulky tyrosines (gpUL37 cleavage site mutant I). Internal cleavage of this UL37x3 mutant was inhibited, verifying usage of the consensus site at amino acids (aa) 193/194. The full-length mitochondrial species of gpUL37 cleavage site mutant I was N glycosylated and endoglycosidase H sensitive, indicating that ER translocation and processing took place prior to its mitochondrial importation. Moreover, these results suggest that internal cleavage of gpUL37 is not necessary for its N glycosylation. Partial deletion or disruption of the UL37 hydrophobic core immediately upstream of the cleavage site resulted in decreased protein abundance, suggesting that the UL37x3 hydrophobic alpha-helix contributes to either correct folding or stability of gpUL37. Insertion of the UL37x3 hydrophobic core and cleavage site into pUL37(M), a splice variant of gpUL37 which lacks these sequences and is neither proteolytically cleaved nor N glycosylated, resulted in its internal cleavage and N glycosylation. Its NH(2)-terminal fragment, pUL37(M-NH2), was detected more abundantly in mitochondria, while its N-glycosylated C-terminal fragment, gpUL37(M-COOH), was detected predominantly in the ER in a manner analogous to that of gpUL37 cleavage products. These results indicate that UL37x3 aa 178 to 205 are prerequisite for gpUL37 internal cleavage and alter UL37 protein topology allowing N glycosylation of its C-terminal sequences. In contrast, the NH(2)-terminal UL37x1 hydrophobic leader, present in pUL37x1, pUL37(M), and gpUL37, is not cleaved from mature UL37 protein, retaining a membrane anchor for UL37 isoforms during trafficking. Taken together, these results suggest that HCMV gpUL37 undergoes sequential trafficking, during which it is ER translocated, processed, and then mitochondrially imported. 相似文献
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The contribution of red cell morphology to the diagnosis of beta-thalassemia trait in a predominantly healthy population was analyzed. The smears from 59 beta-thalassemia trait subjects already identified by DEAE-cellulose microcolumn chromatography, 60 subjects with other forms of microcytosis, and 64 nonmicrocytic subjects were randomly selected and evaluated blind. The "experimental" morphologic criteria were the presence of both basophilic stippling and either microcytosis or target cells. The "control" morphologic criteria were the presence of both microcytosis and poikilocytosis. Although the sensitivity of both sets of criteria were only moderate (73%), the specificity and predictive value of the experimental criteria were very high (99% and 98% respectively). 相似文献
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Manohara Reddy SA Mudgal J Bansal P Vasanthraju SG Srinivasan KK Rao CM Gopalan Kutty N 《Bioorganic & medicinal chemistry》2011,19(1):384-392
A series of 19 heterocyclic homoprostanoids were synthesized from easily available oleic and ricinoleic acids and evaluated for their possible antioxidant, anti-inflammatory and anti-hyperlipidaemic activities. Compounds with thioxo- and oxoimidazole ring (1) and (2) have shown potent antioxidant activity with IC50 values 0.23 ± 0.09 and 0.41 ± 0.01 mM comparable with standard ascorbic acid. Compound (3) with a quinoxaline ring showed maximum inhibition of BSA denaturation at 1 mM concentration and comparable with standard diclofenac. Incorporation of electron withdrawing substitutions like chloro- and nitro-groups in the quinoxaline ring has resulted in an increase anti-inflammatory activity. Test compounds (3), (3a) and (3c) showed modest inhibition of DPP-IV in vitro. However, the unsubstituted quinoxaline (3) and substituted quinoxalines (3b and 3c) reduced plasma glucose levels indicating the presence of hypoglycemic activity. 相似文献
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Madhusmita Dehingia Supriyo Sen Bhuwan Bhaskar Tulsi K. Joishy Manab Deka Narayan C. Talukdar Mojibur R. Khan 《Metabolomics : Official journal of the Metabolomic Society》2017,13(6):69