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1.
Bodil Kjær Yean-Sung Jung Lian Yu John H. Golbeck Henrik Vibe Scheller 《Photosynthesis research》1994,41(1):105-114
The photosynthetic reaction center complex from the green sulfur bacteriumChlorobium vibrioforme has been isolated under anaerobic conditions. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis reveals polypeptides with apparent molecular masses of 80, 40, 30, 18, 15, and 9 kDa. The 80- and 18-kDa polypeptides are identified as the reaction center polypeptide and the secondary donor cytochromec
551 encoded by thepscA andpscC genes, respectively. N-terminal amino acid sequences identify the 40-kDa polypeptide as the bacteriochlorophylla-protein of the baseplate (the Fenna-Matthews-Olson protein) and the 30-kDa polypeptide as the putative 2[4Fe-4S] protein encoded bypscB. Electron paramagnetic resonance (EPR) analysis shows the presence of an iron-sulfur cluster which is irreversibly photoreduced at 9K. Photoaccumulation at higher temperature shows the presence of an additional photoreduced cluster. The EPR spectra of the two iron-sulfur clusters resemble those of FA and FB of Photosystem I, but also show significantly differentg-values, lineshapes, and temperature and power dependencies. We suggest that the two centers are designated Center I (with calculatedg-values of 2.085, 1.898, 1.841), and Center II (with calculatedg-values of 2.083, 1.941, 1.878). The data suggest that Centers I and II are bound to thepscB polypeptide. 相似文献
2.
3.
Bodil Friis-Nielsen 《Plant and Soil》1973,39(3):661-673
Summary Patterns of variations in dry matter concentrations in tomato plants reflected production and translocation of dry matter, implying the possibility of controlling and regulating growth and development of plants by use of dry matter concentration as a useful parameter.Dry matter concentrations, analogous to nutrient concentrations, varied depending on growth conditions, and on type, age and position of plant organs.Interpretation of patterns of variations in contents and concentrations of leaf dry matter in plants, grown under widely different conditions, agreed with the source/sink hypothesis.High water applications were associated with high dry matter concentrations in upper leaves of young pot plants with low sink capacity and with low dry matter concentrations in leaves of older, trough-grown plants with high sink capacity.Accumulation of dry matter in upper leaves of plants is suggested to be associated with development of secondary sinks and, accumulation of dry matter in lateral shoots is considered as a possible explanation of apical dominance.Water regime and transpiration influenced distribution of contents of dry and fresh matter and of absorbed nutrient elements. Redistribution was influenced by water regime.The term, distribution is in the following used in connection with not only absolute values (contents) but also relative values (concentrations). 相似文献
4.
Josep Vilardell John Mundy Bodil Stilling Bernard Leroux Maria Pla Georges Freyssinet Montserrat Pagès 《Plant molecular biology》1991,17(5):985-993
The maizerab17 gene is expressed in different plant parts in response to ABA and osmotic stress (J. Vilardellet al., Plant Mol Biol 14 (1990) 423–432). Here we demonstrate that 5 upstream sequences of therab17 gene confer the appropriate patterns of expression on the chloramphenicol acetyl transferase (CAT) reporter gene in transgenic tobacco plants, as well as in protoplasts derived from cultured rice cells. Specifically, a CAT construct containing a large 5 upstream fragment ofrab17 (–1330/+29) results in high levels of CAT activity in embryos, leaves and roots of transgenic plants subjected to water stress or ABA treatment. Transient expression assays in rice protoplasts transfected with CAT genes fused torab17 promoter deletions indicate that a 300 bp DNA fragment (–351/–102) is sufficient to confer ABA responsiveness upon the reporter gene. Furthermore, a 100 bp sequence (–219/–102) is capable of conferring ABA responsiveness upon a minimal promoter derived from the 35S CaMV promoter. Gel retardation experiments indicate that maize nuclear proteins bind to this fragment. This region of 100 bp contains a sequence (ACGTGGC) which has been identified as an abscisic acid response element in studies of other ABA-responsive plant genes. 相似文献
5.
We tested the hypothesis that changed microclimate at induced forest edges causes reduced growth of epiphytic lichens. Two
foliose, green algal lichens were transplanted to the lower canopy of a mature Picea abies forest at six distances (2, 6.25, 12.5, 25, 50 and 100 m) from a clearcut. The biomass growth in Platismatia glauca (6.2% in 16 months) was 41% higher than in Lobaria pulmonaria (4.4%). We found no growth reduction near the forest edge. In contrast, the highest growth in both species occurred within
12 m from the edge. Further, fluorescence and chlorophyll measurements showed that lichen vitality was unaffected by distance
from edge. The light intensity was 4.3 times higher at the edge than in the interior during the growing season, but there
were only minor differences in air temperature and relative humidity. Monitoring of thallus water content revealed clear differences
in both number and length of wetting and drying cycles. However, the total time with water content sufficient for photosynthetic
activity was only slightly higher at the edge. The data thus indicate that our gradient in microclimate was too small to significantly
affect lichen growth, and that lichens are largely metabolically inactive when large edge-interior contrasts in microclimate
occur. Lichen response to forest edge microclimate results from intricate interactions among several biotic and abiotic factors.
Linking data on lichen growth, microclimate and thallus water content with physiological measurements provides a framework
for future studies of the mechanisms behind abiotic edge effects.
Received: 15 April 1996 / Accepted: 21 June 1996 相似文献
6.
Jens M. Olesen Yoko L. Dupont Bodil K. Ehlers Alfredo Valido Dennis M. Hansen 《Nordic Journal of Botany》2003,23(5):537-539
Jasminum odoratissimum is a Madeira and Canary Islands endemic showing classic heterostyly, i.e. with long-styled flowers with anthers at a low level in the corolla tube and short-styled flowers with anthers at a high level in the corolla tube. Short-styled flowers have large pollen, whereas long-styled flowers have small pollen. The two types are present in equal frequencies in the population. 相似文献
7.
Drabløs F Feyzi E Aas PA Vaagbø CB Kavli B Bratlie MS Peña-Diaz J Otterlei M Slupphaug G Krokan HE 《DNA Repair》2004,3(11):1389-1407
Alkylation lesions in DNA and RNA result from endogenous compounds, environmental agents and alkylating drugs. Simple methylating agents, e.g. methylnitrosourea, tobacco-specific nitrosamines and drugs like temozolomide or streptozotocin, form adducts at N- and O-atoms in DNA bases. These lesions are mainly repaired by direct base repair, base excision repair, and to some extent by nucleotide excision repair (NER). The identified carcinogenicity of O(6)-methylguanine (O(6)-meG) is largely caused by its miscoding properties. Mutations from this lesion are prevented by O(6)-alkylG-DNA alkyltransferase (MGMT or AGT) that repairs the base in one step. However, the genotoxicity and cytotoxicity of O(6)-meG is mainly due to recognition of O(6)-meG/T (or C) mispairs by the mismatch repair system (MMR) and induction of futile repair cycles, eventually resulting in cytotoxic double-strand breaks. Therefore, inactivation of the MMR system in an AGT-defective background causes resistance to the killing effects of O(6)-alkylating agents, but not to the mutagenic effect. Bifunctional alkylating agents, such as chlorambucil or carmustine (BCNU), are commonly used anti-cancer drugs. DNA lesions caused by these agents are complex and require complex repair mechanisms. Thus, primary chloroethyl adducts at O(6)-G are repaired by AGT, while the secondary highly cytotoxic interstrand cross-links (ICLs) require nucleotide excision repair factors (e.g. XPF-ERCC1) for incision and homologous recombination to complete repair. Recently, Escherichia coli protein AlkB and human homologues were shown to be oxidative demethylases that repair cytotoxic 1-methyladenine (1-meA) and 3-methylcytosine (3-meC) residues. Numerous AlkB homologues are found in viruses, bacteria and eukaryotes, including eight human homologues (hABH1-8). These have distinct locations in subcellular compartments and their functions are only starting to become understood. Surprisingly, AlkB and hABH3 also repair RNA. An evaluation of the biological effects of environmental mutagens, as well as understanding the mechanism of action and resistance to alkylating drugs require a detailed understanding of DNA repair processes. 相似文献
8.
Selection of bacteria originating from a human intestinal microbiota in the gut of previously germ-free rats 总被引:1,自引:0,他引:1
Denaturing gradient gel electrophoresis (DGGE) was applied to separate PCR-amplified 16S rRNA genes originating from human microbiota associated (HMA) rat faeces as well as from the human faecal sample used for inoculation of the animals. Subsequently, a total of 15 dominant bands were excised from the DGGE gels, cloned and sequenced. Comparison of the obtained sequences with the Ribosomal Database revealed that species of Bacteroides/Prevotella and Faecalibacterium gave rise to the majority of the dominant bands in the human sample and in the HMA rats. In the HMA rats, two dominant bands, which were not present in the human DGGE profile, originated from species of Ruminococcus. With the exception of the Ruminococcus sequences, sequences originating from both rats and human samples were represented in all major branches of a maximum parsimony tree, indicating that the rat feed and gut environment allows colonization of the dominant taxonomic units from the human microbiota, but additionally selects for Ruminococci. Bands representing Prevotella and Faecalibacterium, which were found in identical positions of the DGGE gels originating from human and HMA rat faecal samples, originated from completely identical sequences, indicating that the same strains of these species were dominating in the human and rat samples. 相似文献
9.
Background and AimsHorizontal gene transfer (HGT) is an important evolutionary mechanism because it transfers genetic material that may code for traits or functions between species or genomes. It is frequent in mitochondrial and nuclear genomes but has not been demonstrated between plastid genomes of different green land plant species.MethodsWe Sanger-sequenced the nuclear internal transcribed spacers (ITS1 and 2) and the plastid rpl16 G2 intron (rpl16). In five individuals with foreign rpl16 we also sequenced atpB-rbcL and trnLUAA-trnFGAA.Key ResultsWe discovered 14 individuals of a moss species with typical nuclear ITSs but foreign plastid rpl16 from a species of a distant lineage. None of the individuals with three plastid markers sequenced contained all foreign markers, demonstrating the transfer of plastid fragments rather than the entire plastid genome, i.e. entire plastids were not transferred. The two lineages diverged 165–185 Myr BP. The extended time interval since lineage divergence suggests that the foreign rpl16 is more likely explained by HGT than by hybridization or incomplete lineage sorting.ConclusionsWe provide the first conclusive evidence of interspecific plastid-to-plastid HGT among land plants. Two aspects are critical: it occurred at several localities during the massive colonization of recently disturbed open habitats that were created by large-scale liming as a freshwater biodiversity conservation measure; and it involved mosses whose unique life cycle includes spores that first develop a filamentous protonema phase. We hypothesize that gene transfer is facilitated when protonema filaments of different species intermix intimately when colonizing disturbed early succession habitats. 相似文献
10.