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31.
M. Kluge D. Mollenhauer R. Mollenhauer R. Kape 《Plant biology (Stuttgart, Germany)》1992,105(5):343-344
The bladders of Geosiphon pyriforme, an endosymbiotic consortium of a fungus and the cyanobacterium Nostoc punctiforme, show nitrogenase activity. This suggests that the organism is capable of nitrogen fixation. 相似文献
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Characterization of a novel calcium-binding 90-kDa glycoprotein (BM-90) shared by basement membranes and serum 总被引:4,自引:0,他引:4
The protein BM-90 was solubilized from the mouse Engelbreth-Holm-Swarm tumor with neutral buffers in molar yields lower (15-30%) than found for other basement membrane proteins (e.g. laminin, BM-40). The purified protein was shown to be rich in cysteine (5 mol%) and to change in SDS electrophoresis from an 84-kDa position to a 95-kDa one upon reduction. BM-90 was also shown to be a calcium-binding protein. The N-terminal sequence of BM-90, as well as those of several internal peptides, showed no identity with any known protein sequences, indicating that it is a new protein. Specific radioimmunoassays showed no or only minor cross-reactions with other known basement membrane proteins. Immunological assays demonstrated BM-90 to be present in neutral salt extracts from mouse heart and kidney, in serum (20-40 micrograms/ml) and in the medium of various cultured cells (0.1-1 microgram/ml). The protein in these samples was identical in size to BM-90 purified from the tumor, indicating that negligible degradation occurs during purification. An extracellular matrix localization of BM-90 was shown by immunofluorescence for Reichert's membrane, lens capsules and other basement membranes. Thus, BM-90 appears to be a novel basement membrane protein whose functions remain to be studied. 相似文献
33.
Summary CO2 exchange, the diurnal variations in the levels of malic, citric and isocitric acid, and the labelling pattern after 14CO2 fixation were measured in Sedum acre and Sedum mite growing in situ. As predicted from laboratory experiments, drought changed the gas exchange pattern from a C3 type to a crassulacean acid metabolism (CAM) type. This shift correlated with the development of a diurnal rhythm in the malic acid content. The results of 14CO2 pulse-chase experiments suggest that in well-watered plants a CAM pattern of carbon flow already exists; hence water stress might enhance latent CAM rather than induce it. The in situ CAM performance by the Sedum species appeared to be highly susceptible to modulation by season and external factors, particularly light and temperature.CAM did not substantially contribute to total carbon gain in S. acre and S. mite. During most of their lifecycles the plants grow under conditions that favour CO2 uptake by the C3 pathway rather than by CAM. Hence, despite a capability to feature CAM, the 13C values found in S. acre and S. mite are those of C3 plants.Abbreviations CAM
Crassulacean Acid Metabolism
- PEP-C
Phosphoenolpyruvate-Carboxylase
- DW
Dry weight
Dedicated to Prof. Dr. Dr. h.c. M. Evenari on the occasion of his 75th birthday and to Dr. K.F. Springer 相似文献
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Mridusmita Saikia Ye Fu Mariana Pavon-Eternod Chuan He Tao Pan 《RNA (New York, N.Y.)》2010,16(7):1317-1327
The N1-methyl-Adenosine (m1A58) modification at the conserved nucleotide 58 in the TΨC loop is present in most eukaryotic tRNAs. In yeast, m1A58 modification is essential for viability because it is required for the stability of the initiator-tRNAMet. However, m1A58 modification is not required for the stability of several other tRNAs in yeast. This differential m1A58 response for different tRNA species raises the question of whether some tRNAs are hypomodified at A58 in normal cells, and how hypomodification at A58 may affect the stability and function of tRNA. Here, we apply a genomic approach to determine the presence of m1A58 hypomodified tRNAs in human cell lines and show how A58 hypomodification affects stability and involvement of tRNAs in translation. Our microarray-based method detects the presence of m1A58 hypomodified tRNA species on the basis of their permissiveness in primer extension. Among five human cell lines examined, approximately one-quarter of all tRNA species are hypomodified in varying amounts, and the pattern of the hypomodified tRNAs is quite similar. In all cases, no hypomodified initiator-tRNAMet is detected, consistent with the requirement of this modification in stabilizing this tRNA in human cells. siRNA knockdown of either subunit of the m1A58-methyltransferase results in a slow-growth phenotype, and a marked increase in the amount of m1A58 hypomodified tRNAs. Most m1A58 hypomodified tRNAs can associate with polysomes in varying extents. Our results show a distinct pattern for m1A58 hypomodification in human tRNAs, and are consistent with the notion that this modification fine tunes tRNA functions in different contexts. 相似文献
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Shai Meiri Luciano Avila Aaron M. Bauer David G. Chapple Indraneil Das Tiffany M. Doan Paul Doughty Ryan Ellis Lee Grismer Fred Kraus Mariana Morando Paul Oliver Daniel Pincheira‐Donoso Marco Antonio Ribeiro‐Junior Glenn Shea Omar Torres‐Carvajal Alex Slavenko Uri Roll 《Global Ecology and Biogeography》2020,29(9):1515-1530
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Anna H. York‐Andersen Qinan Hu Benjamin W. Wood Mariana F. Wolfner Timothy T. Weil 《Molecular reproduction and development》2020,87(2):293-304
Egg activation is the essential process in which mature oocytes gain the competency to proceed into embryonic development. Many events of egg activation are conserved, including an initial rise of intracellular calcium. In some species, such as echinoderms and mammals, changes in the actin cytoskeleton occur around the time of fertilization and egg activation. However, the interplay between calcium and actin during egg activation remains unclear. Here, we use imaging, genetics, pharmacological treatment, and physical manipulation to elucidate the relationship between calcium and actin in living Drosophila eggs. We show that, before egg activation, actin is smoothly distributed between ridges in the cortex of the dehydrated mature oocytes. At the onset of egg activation, we observe actin spreading out as the egg swells though the intake of fluid. We show that a relaxed actin cytoskeleton is required for the intracellular rise of calcium to initiate and propagate. Once the swelling is complete and the calcium wave is traversing the egg, it leads to a reorganization of actin in a wavelike manner. After the calcium wave, the actin cytoskeleton has an even distribution of foci at the cortex. Together, our data show that calcium resets the actin cytoskeleton at egg activation, a model that we propose to be likely conserved in other species. 相似文献