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131.
132.
Early embryo development in Fucus distichus is auxin sensitive 总被引:2,自引:0,他引:2
Auxin and polar auxin transport have been implicated in controlling embryo development in land plants. The goal of these studies was to determine if auxin and auxin transport are also important during the earliest stages of development in embryos of the brown alga Fucus distichus. Indole-3-acetic acid (IAA) was identified in F. distichus embryos and mature tissues by gas chromatography-mass spectroscopy. F. distichus embryos accumulate [(3)H]IAA and an inhibitor of IAA efflux, naphthylphthalamic acid (NPA), elevates IAA accumulation, suggesting the presence of an auxin efflux protein complex similar to that found in land plants. F. distichus embryos normally develop with a single unbranched rhizoid, but growth on IAA leads to formation of multiple rhizoids and growth on NPA leads to formation of embryos with branched rhizoids, at concentrations that are active in auxin accumulation assays. The effects of IAA and NPA are complete before 6 h after fertilization (AF), which is before rhizoid germination and cell division. The maximal effects of IAA and NPA are between 3.5 and 5 h AF and 4 and 5.5 h AF, respectively. Although, the location of the planes of cell division was significantly altered in NPA- and IAA-treated embryos, these abnormal divisions occurred after abnormal rhizoid initiation and branching was observed. The results of this study suggest that auxin acts in the formation of apical basal patterns in F. distichus embryo development. 相似文献
133.
Gravity plays a fundamental role in plant growth and development, yet little is understood about the early events of gravitropism. To identify genes affected in the signal perception and/or transduction phase of the gravity response, a mutant screen was devised using cold treatment to delay the gravity response of inflorescence stems of Arabidopsis. Inflorescence stems of Arabidopsis show no response to gravistimulation at 4 degrees C for up to 3 h. However, when gravistimulated at 4 degrees C and then returned to vertical at room temperature (RT), stems bend in response to the previous, horizontal gravistimulation (H. Fukaki, H. Fujisawa, M. Tasaka [1996] Plant Physiology 110: 933-943). This indicates that gravity perception, but not the gravitropic response, occurs at 4 degrees C. Recessive mutations were identified at three loci using this cold effect on gravitropism to screen for gravity persistence signal (gps) mutants. All three mutants had an altered response after gravistimulation at 4 degrees C, yet had phenotypically normal responses to stimulations at RT. gps1-1 did not bend in response to the 4 degrees C gravity stimulus upon return to RT. gps2-1 responded to the 4 degrees C stimulus but bent in the opposite direction. gps3-1 over-responded after return to RT, continuing to bend to an angle greater than wild-type plants. At 4 degrees C, starch-containing statoliths sedimented normally in both wild-type and the gps mutants, but auxin transport was abolished at 4 degrees C. These results are consistent with GPS loci affecting an aspect of the gravity signal perception/transduction pathway that occurs after statolith sedimentation, but before auxin transport. 相似文献
134.
135.
Molecular and physiological analysis of Arabidopsis mutants defective in cytosolic or chloroplastic aspartate aminotransferase 总被引:7,自引:0,他引:7
A single, recessive mutation in soybean (Glycine max L. Merr.), which confers a seed phenotype of increased inorganic phosphate, decreased phytic acid, and a decrease in total raffinosaccharides, has been previously disclosed (S.A. Sebastian, P.S. Kerr, R.W. Pearlstein, W.D. Hitz [2000] Soy in Animal Nutrition, pp 56-74). The genetic lesion causing the multiple changes in seed phenotype is a single base change in the third base of the codon for what is amino acid residue 396 of the mature peptide encoding a seed-expressed myo-inositol 1-phospate synthase gene. The base change causes residue 396 to change from lysine to asparagine. That amino acid change decreases the specific activity of the seed-expressed myo-inositol 1-phosphate synthase by about 90%. Radio tracer experiments indicate that the supply of myo-inositol to the reaction, which converts UDP-galactose and myo-inositol to galactinol is a controlling factor in the conversion of total carbohydrate into the raffinosaccharides in both wild-type and mutant lines. That same decrease in myo-inositol 1-phosphate synthetic capacity leads to a decreased capacity for the synthesis of myo-inositol hexaphosphate (phytic acid) and a concomitant increase in inorganic phosphate. 相似文献
136.
Vargas-Requena CL Hernández-Santoyo A Yepiz-Plascencia G Vargas-Albores F Higuera-Ciapara I Rodríguez-Romero A Soulages JL Sotelo-Mundo RR 《Protein and peptide letters》2002,9(4):337-344
Crustacean High Density Lipoprotein/beta-Glucan Binding Protein (HDL/BGBP) has been studied due to its role in nutrition and immune response via activation of the defense cells (hemocytes) upon binding 1,3-D-beta-glucan carbohydrates. In this study, HDL/BGBP was found to be composed mainly of beta sheets, as determined by circular dichroism. Lipoprotein aggregation resulted when HDL/BGBP interacted with phospolipid vesicles, laminaribiose (1,3-beta-glucan disaccharide) or heparin. HDL/BGBP has similar dissociation constants for laminaribiose (K(d)=22 mM) or heparin (K(d)=46 mM) as determined by 90 degrees light scattering. 相似文献
137.
Arabidopsis glt1-T mutant defines a role for NADH-GOGAT in the non-photorespiratory ammonium assimilatory pathway 总被引:1,自引:0,他引:1
Lancien M Martin M Hsieh MH Leustek T Goodman H Coruzzi GM 《The Plant journal : for cell and molecular biology》2002,29(3):347-358
The physiological role of the NADH-dependent glutamine-2-oxoglutarate aminotransferase (NADH-GOGAT) enzyme was addressed in Arabidopsis using gene expression analysis and by the characterization of a knock-out T-DNA insertion mutant (glt1-T) in the single NADH-GOGAT GLT1 gene. The NADH-GOGAT GLT1 mRNA is expressed at higher levels in roots than in leaves. This expression pattern contrasts with GLU1, the major gene encoding Fd-GOGAT, which is most highly expressed in leaves and is involved in photorespiration. These distinct organ-specific expression patterns suggested a non-redundant physiological role for the NADH-GOGAT and Fd-GOGAT gene products. To test the in vivo function of NADH-GOGAT, we conducted molecular and physiological analysis of the glt1-T mutant, which is null for NADH-GOGAT, as judged by mRNA level and enzyme activity. Metabolic analysis showed that the glt1-T mutant has a specific defect in growth and glutamate biosynthesis when photorespiration was repressed by 1% CO2. Under these conditions, the glt1-T mutant displayed a 20% decrease in growth and a dramatic 70% reduction in glutamate levels. Herein, we discuss the significance of NADH-GOGAT in non-photorespiratory ammonium assimilation and in glutamate synthesis required for plant development. 相似文献
138.
Systematics of basidiomycetous yeasts: a comparison of large subunit D1/D2 and internal transcribed spacer rDNA regions 总被引:7,自引:0,他引:7
Basidiomycetous yeasts in the Urediniomycetes and Hymenomycetes were examined by sequence analysis in two ribosomal DNA regions: the D1/D2 variable domains at the 5' end of the large subunit rRNA gene (D1/D2) and the internal transcribed spacers (ITS) 1 and 2. Four major lineages were recognized in each class: Microbotryum, Sporidiobolus, Erythrobasidium and Agaricostilbum in the Urediniomycetes; Tremellales, Trichosporonales, Filobasidiales and Cystofilobasidiales in the Hymenomycetes. Bootstrap support for many of the clades within those lineages is weak; however, phylogenetic analysis provides a focal point for in-depth study of biological relationships. Combined sequence analysis of the D1/D2 and ITS regions is recommended for species identification, while species definition requires classical biological information such as life cycles and phenotypic characterization. 相似文献
139.
Epoxy sepabeads: a novel epoxy support for stabilization of industrial enzymes via very intense multipoint covalent attachment 总被引:5,自引:0,他引:5
Mateo C Abian O Fernández-Lorente G Pedroche J Fernández-Lafuente R Guisan JM Tam A Daminati M 《Biotechnology progress》2002,18(3):629-634
Sepabeads-EP (a new epoxy support) has been utilized to immobilize-stabilize the enzyme penicillin G acylase (PGA) via multipoint covalent attachment. These supports are very robust and suitable for industrial purposes. Also, the internal geometry of the support is composed by cylindrical pores surrounded by the convex surfaces (this offers a good geometrical congruence for reaction with the enzyme), and it has a very high superficial density of epoxy groups (around 100 micromol/mL). These features should permit a very intense enzyme-support interaction. However, the final stability of the immobilized enzyme is strictly dependent on the immobilization protocol. By using conventional immobilization protocols (neutral pH values, nonblockage of the support) the stability of the immobilized enzyme was quite similar to that achieved using Eupergit C to immobilize the PGA. However, when using a more sophisticated three-step immobilization/stabilization/blockage procedure, the Sepabeads derivative was hundreds-fold more stable than Eupergit C derivatives. The protocol used was as follows: (i) the enzyme was first covalently immobilized under very mild experimental conditions (e.g., pH 7.0 and 20 degrees C); (ii) the already immobilized enzyme was further incubated under more drastic conditions (higher pH values, long incubation periods, etc.) in order to "facilitate" the formation of new covalent linkages between the immobilized enzyme molecule and the support; (iii) the remaining epoxy groups of the support were blocked with very hydrophilic compounds to stop any additional interaction between the enzyme and the support. This third point was found to be critical for obtaining very stable enzymes: derivatives blocked with mercaptoethanol were much less stable than derivatives blocked with glycine or other amino acids. This was attributed to the better masking of the hydrophobicity of the support by the amino acids (having two charges). 相似文献
140.
Maniscalco WM Watkins RH Pryhuber GS Bhatt A Shea C Huyck H 《American journal of physiology. Lung cellular and molecular physiology》2002,282(4):L811-L823
Proper formation of the pulmonary microvasculature is essential for normal lung development and gas exchange. Lung microvascular development may be disrupted by chronic injury of developing lungs in clinical diseases such as bronchopulmonary dysplasia. We examined microvascular development, angiogenic growth factors, and endothelial cell receptors in a fetal baboon model of chronic lung disease (CLD). In the last third of gestation, the endothelial cell marker platelet endothelial cell adhesion molecule (PECAM)-1 increased 7.5-fold, and capillaries immunostained for PECAM-1 changed from a central location in airspace septa to a subepithelial location. In premature animals delivered at 67% of term and supported with oxygen and ventilation for 14 days, PECAM-1 protein and capillary density did not increase, suggesting failure to expand the capillary network. The capillaries of the CLD animals were dysmorphic and not subepithelial. The angiogenic growth factor vascular endothelial growth factor (VEGF) and its receptor fms-like tyrosine kinase receptor (Flt-1) were significantly decreased in CLD. Angiopoietin-1, another angiogenic growth factor, and its receptor tyrosine kinase with immunoglobulin and epidermal growth factor homology domains were not significantly changed. These data suggest that CLD impairs lung microvascular development and that a possible mechanism is disruption of VEGF and Flt-1 expression. 相似文献