R-loop-dependent rolling-circle replication and a new model for DNA concatemer resolution by mitochondrial plasmid mp1.
(1/16)
The mitochondrial (mt) plasmid mp1 of Chenopodium album replicates by a rolling-circle (RC) mechanism initiated at two double-stranded replication origins (dso1 and dso2). Two-dimensional gel electrophoresis and electron microscopy of early mp1 replication intermediates revealed novel spots. Ribonucleotide (R)-loops were identified at dso1, which function as a precursor for the RCs in vivo and in vitro. Bacteriophage T4-like networks of highly branched mp1 concatemers with up to 20 monomer units were mapped and shown to be mainly formed by replicating, invading, recombining and resolving molecules. A new model is proposed in which concatemers were separated into single units by a "snap-back" mechanism and homologous recombination. dso1 is a recombination hotspot, with sequence homology to bacterial Xer recombination cores. mp1 is a unique eukaryotic plasmid that expresses features of phages like T4 and could serve as a model system for replication and maintenance of DNA concatemers. (+info)
Ribosome-inactivating activity and cDNA cloning of antiviral protein isoforms of Chenopodium album.
(2/16)
We have characterized a novel type I ribosome-inactivating protein (CAP30) from the leaves of Chenopodium album. Purified native CAP30 depurinated the ribosomes of Chenopodium, tomato, and tobacco leaves in vitro. To further characterize this protein, cDNA clones were isolated from a leaf cDNA library using a DNA probe derived from the N-terminal amino acid sequence. Two full-length cDNA clones, CAP30A and CAP30B, were isolated. The two clones were highly homologous (91.4% identity over 280 amino acids) at the deduced amino acid level. Both contain a putative signal peptide of 25 amino acid and a conserved domain commonly found in ribosome-inactivating proteins. This suggests that CAP30 is a single-chain ribosome-inactivating protein. Expression of CAP30 mRNA peaked twice, at 12 and 72 h, after tobacco mosaic virus (TMV) infection or wounding. Transformed Escherichia coli cells expressing pre- or mature CAP had greatly reduced growth rates. These results suggest that CAP30 functions as a broad-spectrum defense-related protein with both antiviral and anti-microbial activity. (+info)
Amelioration of biodiversity impacts of genetically modified crops: predicting transient versus long-term effects.
(3/16)
It has been suggested that genetically modified herbicide-tolerant crops may benefit biodiversity because spraying of crops may be delayed until later in the growing season, allowing weeds to grow during the early part of the year. This provides an enhanced resource for arthropods, and potentially benefits birds that feed on these. Thus, this technology could enhance biodiversity. Using a review of weed phenologies and a population model, we show that many weeds are unlikely to benefit because spraying is generally delayed insufficiently late in the season to allow most to set seed. The positive effects on biodiversity observed in trials lasting one or two seasons are thus likely to be transient. For one weed of particular significance (Chenopodium album, fat hen) we show that it is unlikely that the positive effects observed could be maintained by inputs of seed during other parts of the rotation. However, we find preliminary evidence that if spraying can be ceased earlier in the season, then a viable population of late-emerging weeds could be maintained. This strategy could benefit weeds in both genetically modified (GM) and non-GM crops, but would probably lead to reduced inputs in GM systems compared with conventional ones. (+info)
Applicability and limitations of optimal biomass allocation models: a test of two species from fertile and infertile habitats.
(4/16)
BACKGROUND AND AIMS: The practical applicability of optimal biomass allocation models is not clear. Plants may have constraints in the plasticity of their root : leaf ratio that prevent them from regulating their root : leaf ratio in the optimal manner predicted by the models. The aim of this study was to examine the applicability and limitations of optimal biomass allocation models and to test the assumption that regulation of the root : leaf ratio enables maximization of the relative growth rate (RGR). METHODS: Polygonum cuspidatum from an infertile habitat and Chenopodium album from a fertile habitat were grown under a range of nitrogen availabilities. The biomass allocation, leaf nitrogen concentration (LNC), RGR, net assimilation rate (NAR), and leaf area ratio (LAR) of each species were compared with optimal values determined using an optimal biomass allocation model. KEY RESULTS: The root : leaf ratio of C. album was smaller than the optimal ratio in the low-nitrogen treatment, while it was almost optimal in the high-nitrogen treatment. In contrast, the root : leaf ratio of P. cuspidatum was close to the optimum under both high- and low-nitrogen conditions. Owing to the optimal regulation of the root : leaf ratio, C. album in the high-nitrogen treatment and P. cuspidatum in both treatments had LNC and RGR (with its two components, NAR and LAR) close to their optima. However, in the low-nitrogen treatment, the suboptimal root : leaf ratio of C. album led to a smaller LNC than the optimum, which in turn resulted in a smaller NAR than the optimum and RGR than the theoretical maximum RGR. CONCLUSIONS: The applicability of optimal biomass allocation models is fairly high, although constraints in the plasticity of biomass allocation could prevent optimal regulation of the root : leaf ratio in some species. The assumption that regulation of the root : leaf ratio enables maximization of RGR was supported. (+info)
Occupational rhinitis due to pepsin.
(5/16)
A woman presented work-related rhinoconjunctivitis due to inhalation of pepsin used in a slaughterhouse. Prick tests and conjunctival challenge were positive to pepsin. Serum specific IgE to pepsin was 5.58 kU/L and an IgE-binding band of 43 kDa was detected in SDS-PAGE Immunoblotting. Rhinoconjunctivitis improved clearly when the patient was assigned to another place without contact with pepsin. Pepsin has been previously reported to cause occupational allergic asthma on three occasions. As far as we know, this is the first reported case in which an IgE-immunoblot has been performed. (+info)
Three-dimensional structure of the cross-reactive pollen allergen Che a 3: visualizing cross-reactivity on the molecular surfaces of weed, grass, and tree pollen allergens.
(6/16)
Two EF-hand calcium-binding allergens (polcalcins) occur in the pollen of a wide variety of unrelated plants as highly cross-reactive allergenic molecules. We report the expression, purification, immunological characterization, and the 1.75-A crystal structure of recombinant Che a 3 (rChe a 3), the polcalcin from the weed Chenopodium album. The three-dimensional structure of rChe a 3 resembles an alpha-helical fold that is essentially identical with that of the two EF-hand allergens from birch pollen, Bet v 4, and timothy grass pollen, Phl p 7. The extensive cross-reactivity between Che a 3 and Phl p 7 is demonstrated by competition experiments with IgE Abs from allergic patients as well as specific Ab probes. Amino acid residues that are conserved for the two EF-hand allergen family were identified in multiple sequence alignments of polcalcins from 15 different plants. Next, the three-dimensional structures of rChe a 3, rPhl p 7, and rBet v 4 were used to identify conserved amino acids with high surface exposition to visualize surface patches as potential targets for the polyclonal IgE Ab response of allergic patients. The essentially identical three-dimensional structures of rChe a 3, rPhl p 7, and rBet v 4 explain the extensive cross-reactivity of allergic patients IgE Abs with two EF-hand allergens from unrelated plants. In addition, analyzing the three-dimensional structures of cross-reactive Ags for conserved and surface exposed amino acids may be a first approach to mapping the conformational epitopes on disease-related Ags that are recognized by polyclonal patient Abs. (+info)
Co-administration of CpG oligonucleotides and chenopodium album extract reverse IgG2a/IgG1 ratios and increase IFN-gamma and IL-10 productions in a murine model of asthma.
(7/16)