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91.
Disruption of the FATB gene in Arabidopsis demonstrates an essential role of saturated fatty acids in plant growth 总被引:3,自引:0,他引:3 下载免费PDF全文
Acyl-acyl carrier protein thioesterases determine the amount and type of fatty acids that are exported from the plastids. To better understand the role of the FATB class of acyl-acyl carrier protein thioesterases, we identified an Arabidopsis mutant with a T-DNA insertion in the FATB gene. Palmitate (16:0) content of glycerolipids of the mutant was reduced by 42% in leaves, by 56% in flowers, by 48% in roots, and by 56% in seeds. In addition, stearate (18:0) was reduced by 50% in leaves and by 30% in seeds. The growth rate was reduced in the mutant, resulting in 50% less fresh weight at 4 weeks compared with wild-type plants. Furthermore, mutant plants produced seeds with low viability and altered morphology. Analysis of individual glycerolipids revealed that the fatty acid composition of prokaryotic plastid lipids was largely unaltered, whereas the impact on eukaryotic lipids varied but was particularly severe for phosphatidylcholine, with a >4-fold reduction of 16:0 and a 10-fold reduction of 18:0 levels. The total wax load of fatb-ko plants was reduced by 20% in leaves and by 50% in stems, implicating FATB in the supply of saturated fatty acids for wax biosynthesis. Analysis of C(18) sphingoid bases derived from 16:0 indicated that, despite a 50% reduction in exported 16:0, the mutant cells maintained wild-type levels of sphingoid bases, presumably at the expense of other cell components. The growth retardation caused by the fatb mutation was enhanced in a fatb-ko act1 double mutant in which saturated fatty acid content was reduced further. Together, these results demonstrate the in vivo role of FATB as a major determinant of saturated fatty acid synthesis and the essential role of saturates for the biosynthesis and/or regulation of cellular components critical for plant growth and seed development. 相似文献
92.
Role of diffusible and transcription factors in inner ear development: implications in regeneration 总被引:3,自引:0,他引:3
Frago LM Camerero G Cañón S Pañeda C Sanz C Leon Y Giraldez F Varela-Nieto I 《Histology and histopathology》2000,15(2):657-666
Organogenesis involves a dynamic balance of the mechanisms regulating cell division, differentiation and death. The development of the chicken embryo inner ear offers a well-characterised model at the morphological level to study which signals are implicated in the modulation of cellular activation and commitment. The early developmental decisions that control the origin of the inner ear elements are just beginning to be identified by complementary in vivo and in vitro studies. Insulin-like growth factor-I (IGF-I) and nerve growth factor (NGF) are among the best characterised diffusible factors acting during inner ear development. Although the cellular actions of these factors are beginning to be understood, the signalling pathways triggered by them still remain largely unknown. In this context, viral vehicles can be used to deliver genes and then analyse their functional roles during inner ear development. A model is proposed where the actions of IGF-I and NGF contribute to the combinatorial expression of Jun and Fos family members in particular domains of the otic vesicle. Some of these mechanisms may be also implicated in otic regeneration. 相似文献
93.
Regulatory interactions between the Reg1-Glc7 protein phosphatase and the Snf1 protein kinase 下载免费PDF全文
Protein phosphatase 1, comprising the regulatory subunit Reg1 and the catalytic subunit Glc7, has a role in glucose repression in Saccharomyces cerevisiae. Previous studies showed that Reg1 regulates the Snf1 protein kinase in response to glucose. Here, we explore the functional relationships between Reg1, Glc7, and Snf1. We show that different sequences of Reg1 interact with Glc7 and Snf1. We use a mutant Reg1 altered in the Glc7-binding motif to demonstrate that Reg1 facilitates the return of the activated Snf1 kinase complex to the autoinhibited state by targeting Glc7 to the complex. Genetic evidence indicated that the catalytic activity of Snf1 negatively regulates its interaction with Reg1. We show that Reg1 is phosphorylated in response to glucose limitation and that this phosphorylation requires Snf1; moreover, Reg1 is dephosphorylated by Glc7 when glucose is added. Finally, we show that hexokinase PII (Hxk2) has a role in regulating the phosphorylation state of Reg1, which may account for the effect of Hxk2 on Snf1 function. These findings suggest that the phosphorylation of Reg1 by Snf1 is required for the release of Reg1-Glc7 from the kinase complex and also stimulates the activity of Glc7 in promoting closure of the complex. 相似文献
94.
The eukaryotic acidic P1 and P2 proteins modulate the activity of the ribosomal stalk but playing distinct roles. The aim of this work was to analyze the structural features that are behind their different function. A structural characterization of Saccharomyces cerevisaie P1 alpha and P2 beta proteins was performed by circular dichroism, nuclear magnetic resonance, fluorescence spectroscopy, thermal denaturation, and protease sensitivity. The results confirm the low structure present in both proteins but reveal clear differences between them. P1 alpha shows a virtually unordered secondary structure with a residual helical content that disappears below 30 degrees C and a clear tendency to acquire secondary structure at low pH and in the presence of trifluoroethanol. In agreement with this higher disorder P1 alpha has a fully solvent-accessible tryptophan residue and, in contrast to P2 beta, is highly sensitive to protease degradation. An interaction between both proteins was observed, which induces an increase in the global secondary structure content of both proteins. Moreover, mixing of both proteins causes a shift of the P1 alpha tryptophan 40 signal, pointing to an involvement of this region in the interaction. This evidence directly proves an interaction between P1 alpha and P2 beta before ribosome binding and suggests a functional complementation between them. On a whole, the results provide structural support for the different functional roles played by the proteins of the two groups showing, at the same time, that relatively small structural differences between the two stalk acidic protein types can result in significant functional changes. 相似文献
95.
96.
González-Fandos E Giménez M Olarte C Sanz S Simón A 《Journal of applied microbiology》2000,89(4):624-632
Mushrooms were packed in two polymeric films (perforated and non-perforated PVC) and stored at 17 degrees C and 25 degrees C. The carbon dioxide and oxygen content inside the packages, aerobic mesophiles, Pseudomonas spp., faecal coliforms, Escherichia coli, anaerobic spores and major sensory factors (colour, texture, development stage and presence of moulds) were determined. The non-perforated packages had the highest contents of CO2 (6-7%), the lowest contents of O2 (0.013-0.17%) and the most desirable quality parameters (texture, development stage and absence of moulds). Pseudomonas spp. counts were around 1 logarithmic unit lower in mushrooms packaged in non-perforated film as the O2 concentrations were lower than in perforated film. The mushrooms themselves were inoculated with an enterotoxin A-producing strain of Staphylococcus aureus, packaged in overwrapped trays and stored at 17 and 25 degrees C. Staphylococcus aureus did not grow in the samples stored at 17 degrees C. Only slight growth was observed in mushrooms packaged with non-perforated film after 1 day at 25 degrees C. No enterotoxin was detected in any package. Faecal coliform counts were <2 log cfu g(-1). Escherichia coli was not isolated in any of the samples. At 25 degrees C, counts of anaerobic spores of around 2 log cfu g(-1) were detected in those mushrooms packaged in non-perforated film. 相似文献
97.
SUMMARY: MIPSIM is a computational package designed to analyse and compare 3D distributions of molecular interaction potentials (MIP) of series of biomolecules. 相似文献
98.
A mathematical model to calculate the amount of ice formed instantaneously after a rapid expansion in high-pressure shift processes (HPSF) was developed. It considers that when water is expanded it does not extend over its melting curve but reaches a metastable state (supercooled water), which also occurs in practice. Theoretical results appear to agree with experimental data. 相似文献
99.
Lorda-Sanchez I Garcia-Ruiz PJ Rodriguez de Alba M Montoya J Playan A Sarasa JL Trujillo MJ Sanz R Ramos C Ayuso C 《Genetic counseling (Geneva, Switzerland)》2000,11(3):261-265
A MELAS phenotype and a paternal inherited inversion of chromosome 10 in a female patient: We describe a patient suffering from encephalomyopathy with overlapping symptoms, including MELAS and Kearn-Sayre syndrome features. Mutations in tRNA LEU (UUR) were not found in mtDNA of blood cells, suggesting a different genetic defect. Cytogenetic studies revealed a paternal inherited pericentric inversion of chromosome 10 (p13;q22) pat. Although the presence of the same inversion in the father and in the apparently asymptomatic sister does rather suggest that the concurrence of the mitochondrial disease in the patient was due to chance, some alternative explanations to associate both events might be proposed. 相似文献
100.
Iron deficiency in peach trees: effects on leaf chlorophyll and nutrient concentrations in flowers and leaves 总被引:3,自引:0,他引:3
Belkhodja Ramzi Morales Fermín Sanz Manuel Abadía Anunciación Abadía Javier 《Plant and Soil》1998,203(2):257-268
The effects of iron deficiency on the leaf chlorophyll concentrations and on the macro- (N, P, K, Ca and Mg) and micro-nutrient (Fe, Mn, Zn and Cu) composition of flowers (at full bloom) and leaves (60 and 120 days after full bloom) of field-grown peach (Prunus persica L. Batsch) trees were investigated. Flowers and leaves were taken and analysed from fifty individual trees. Our data indicate that large decreases in leaf chlorophyll concentration were found at the beginning of the season in control trees, possibly associated to a dilution effect by leaf growth, that were later followed by leaf chlorophyll concentration increases. Leaf Fe chlorosis apparently results from two different processes, the dilution of leaf Chl caused by growth and the subsequent inability to produce and/or stabilize new Chl molecules in the thylakoid membrane. Iron chlorosis did not change the seasonal change patterns of any of the nutrients studied. In Fe-deficient trees the K concentration and the K/Ca ratio were high not only in leaves but also in flowers, indicating that this is a characteristic of Fe-deficient plant tissue in the whole fruit tree growing season. Flower Fe concentrations were well correlated with the degree of chlorosis developed later in the season by the trees, suggesting that flower analysis could be used for the prognosis of Fe deficiency in peach. 相似文献