Orthologs in Arabidopsis thaliana of the Hsp70 interacting protein Hip.
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The Hsp70-interacting protein Hip binds to the adenosine triphosphatase domain of Hsp70, stabilizing it in the adenosine 5'-diphosphate-ligated conformation and promoting binding of target polypeptides. In mammalian cells, Hip is a component of the cytoplasmic chaperone heterocomplex that regulates signal transduction via interaction with hormone receptors and protein kinases. Analysis of the complete genome sequence of the model flowering plant Arabidopsis thaliana revealed 2 genes encoding Hip orthologs. The deduced sequence of AtHip-1 consists of 441 amino acid residues and is 42% identical to human Hip. AtHip-1 contains the same functional domains characterized in mammalian Hip, including an N-terminal dimerization domain, an acidic domain, 3 tetratricopeptide repeats flanked by a highly charged region, a series of degenerate GGMP repeats, and a C-terminal region similar to the Sti1/Hop/p60 protein. The deduced amino acid sequence of AtHip-2 consists of 380 amino acid residues. AtHip-2 consists of a truncated Hip-like domain that is 46% identical to human Hip, followed by a C-terminal domain related to thioredoxin. AtHip-2 is 63% identical to another Hip-thioredoxin protein recently identified in Vitis labrusca (grape). The truncated Hip domain in AtHip-2 includes the amino terminus, the acidic domain, and tetratricopeptide repeats with flanking charged region. Analyses of expressed sequence tag databases indicate that both AtHip-1 and AtHip-2 are expressed in A thaliana and that orthologs of Hip are also expressed widely in other plants. The similarity between AtHip-1 and its mammalian orthologs is consistent with a similar role in plant cells. The sequence of AtHip-2 suggests the possibility of additional unique chaperone functions. (+info)
Effects of natural intensities of visible and ultraviolet radiation on epidermal ultraviolet screening and photosynthesis in grape leaves.
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Grape (Vitis vinifera cv Silvaner) vine plants were cultivated under shaded conditions in the absence of ultraviolet (UV) radiation in a greenhouse, and subsequently placed outdoors under three different light regimes for 7 d. Different light regimes were produced by filters transmitting natural radiation, or screening out the UV-B (280-315 nm), or screening out the UV-A (315-400 nm) and the UV-B spectral range. During exposure, synthesis of UV-screening phenolics in leaves was quantified using HPLC: All treatments increased concentrations of hydroxycinnamic acids but the rise was highest, reaching 230% of the initial value, when UV radiation was absent. In contrast, UV-B radiation specifically increased flavonoid concentrations resulting in more than a 10-fold increase. Transmittance in the UV of all extracted phenolics was lower than epidermal UV transmittance determined fluorimetrically, and the two parameters were curvilinearly related. It is suggested that curvilinearity results from different absorption properties of the homogeneously dissolved phenolics in extracts and of the non-homogeneous distribution of phenolics in the epidermis. UV-B-dependent inhibition of maximum photochemical yield of photosystem II (PSII), measured as variable fluorescence of dark-adapted leaves, recovered in parallel to the buildup of epidermal screening for UV-B radiation, suggesting that PSII is protected against UV-B damage by epidermal screening. However, UV-B inhibition of CO(2) assimilation rates was not diminished by efficient UV-B screening. We propose that protection of UV-B inactivation of PSII is observed because preceding damage is efficiently repaired while those factors determining UV-B inhibition of CO(2) assimilation recover more slowly. (+info)
Rapid deposition of extensin during the elicitation of grapevine callus cultures is specifically catalyzed by a 40-kilodalton peroxidase.
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Elicitation or peroxide stimulation of grape (Vitis vinifera L. cv Touriga) vine callus cultures results in the rapid and selective in situ insolubilization of an abundant and ionically bound cell wall protein-denominated GvP1. Surface-enhanced laser desorption/ionization/time of flight-mass spectrometry analysis, the amino acid composition, and the N-terminal sequence of purified GvP1 identified it as an 89.9-kD extensin. Analysis of cell walls following the in situ insolubilization of GvP1 indicates large and specific increases in the major amino acids of GvP1 as compared with the amino acids present in salt-eluted cell walls. We calculate that following deposition, covalently bound GvP1 contributes up to 4% to 5% of the cell wall dry weight. The deposition of GvP1 in situ requires peroxide and endogenous peroxidase activity. Isoelectric focusing of saline eluates of callus revealed only a few basic peroxidases that were all isolated or purified to electrophoretic homogeneity. In vitro and in situ assays of extensin cross-linking activity using GvP1 and peroxidases showed that a 40-kD peroxidase cross-linked GvP1 within minutes, whereas other grapevine peroxidases had no significant activity with GvP1. Internal peptide sequences indicated this extensin peroxidase (EP) is a member of the class III peroxidases. We conclude that we have identified and purified an EP from grapevine callus that is responsible for the catalysis of GvP1 deposition in situ during elicitation. Our results suggest that GvP1 and this EP play an important combined role in grapevine cell wall defense. (+info)
Sink feedback regulation of photosynthesis in vines: measurements and a model.
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An experimental and modelling study of source-sink interactions in Vitis vinifera L., cv. Cabernet Sauvignon, rooted cuttings under non-limiting environmental conditions with a 12 h photoperiod is presented here. After 4 h, measured photosynthesis, stomatal conductance and leaf carbohydrate content reached maximum values. Over the remainder of the photoperiod, photosynthesis and stomatal conductance decreased continuously, whereas leaf carbohydrate content remained relatively constant. Because the experiment took place in a non-limiting environment, the results suggest that stomatal regulation of photosynthesis was mediated by an internal factor, possibly related to sink activity. A simple 1-source, 2-sink model was developed to examine the extent to which the data could be explained by a hypothetical sink-to-source feedback mechanism mediated by carbohydrate levels in either the mesophyll, the source phloem or the phloem of one of the two sinks. Model simulations reproduced the data well under the hypothesis of a phloem-based feedback signal, although the data were insufficient to elucidate the detailed nature of such a signal. In a sensitivity analysis, the steady-state response of photosynthesis to sink activity was explored and predictions made for the partitioning of photosynthate between the two sinks. The analysis highlights the effectiveness of a phloem-based feedback signal in regulating the balance between source and sink activities. However, other mechanisms for the observed decline in photosynthesis, such as photoinhibition, endogenous circadian rhythms or hydraulic signals in the leaf cannot be excluded. Nevertheless, it is concluded that the phloem-based feedback model developed here may provide a useful working hypothesis for incorporation into plant growth models and for further development and testing. (+info)
Anti-inflammatory effect and mechanism of proanthocyanidins from grape seeds.
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AIM: To investigate the anti-inflammatory effect and mechanism of proanthocyanidins (PA) from grape seeds. METHODS: Croton oil-induced ear swelling in mice and carrageenan-induced hind paw edema in rats were prepared. The nitric oxide synthase (NOS) activity was measured by NADPH-diaphoras stain assay, nitric oxide (NO) content by Griess diazotization assay, N-acetyl-beta- D-glucosaminidase (beta-NAG) activity by spectrophotography, malondialdehyde (MDA) content by thiobarbituric acid (TBA) fluorescence technique, and IL-1beta, TNFalpha, and PGE2 content by radioimmunoassay (RIA). RESULTS: PA 10-40 mg/kg ip inhibited carrageenan-induced paw edema in rats and croton oil-induced ear swelling in mice in a dose-dependent manner. PA 10 mg/kg reduced MDA content in inflamed paws, inhibited beta-NAG and NOS activity, and lowered the content of NO, IL-1beta, TNFalpha, and PGE2 in exudate from edema paws of rats induced by carrageenan. The inhibitory effect of PA on all above indices was more evident than that of dexamethasone 2 mg/kg. CONCLUSION: PA has anti-inflammatory effect on experimental inflammation in rats and mice. Its mechanisms of anti-inflammatory action are relevant to oxygen free radical scavenging, anti-lipid peroxidation, and inhibition of the formation of inflammatory cytokines. (+info)
Purification and characterization of a O-methyltransferase capable of methylating 2-hydroxy-3-alkylpyrazine from Vitis vinifera L. (cv. Cabernet Sauvignon).
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An S-adenosyl-L-methionine-dependent O-methyltransferase capable of methylating 2-hydroxy-3-alkylpyrazine (HP) was purified 7,300-fold to apparent homogeneity with an 8.2% overall recovery from Vitis vinifera L. (cv. Cabernet Sauvignon) through a purification procedure including column chromatography on DEAE-Sepharose FF, Ether-5PW, hydroxyapatite, G2000SW(XL), and DEAE-5PW. The relative molecular mass of the native enzyme estimated on gel permeation chromatography was 85 kDa, and the subunit molecular mass was estimated to be 41 kDa on SDS-polyacrylamide gel electrophoresis. The enzyme also methylates caffeic acid. The Vmax for IBHP and caffeic acid were 0.73 and 175 pkatals/mg, respectively, and the respective Km for IBHP and caffeic acid were 0.30 and 0.032 mm. The optimum pH for IBHP (8.5) was different from that for caffeic acid (7.5). (+info)
The daily oral administration of high doses of trans-resveratrol to rats for 28 days is not harmful.
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trans-3,5,4'-Trihydroxystilbene (trans-resveratrol) is a phytochemical present in peanuts, grapes and wine with beneficial effects such as protection against cardiovascular disease and cancer prevention. The purpose of this study was to evaluate whether high doses of trans-resveratrol have harmful effects on Sprague-Dawley rats. trans-Resveratrol was administered orally to male rats for 28 d at a dose of 20 mg/(kg x d), 1000 times the amount consumed by a 70-kg person taking 1.4 g of trans-resveratrol/d. Body weight, and food and water consumption did not differ between rats treated with trans-resveratrol and the control group. Hematologic and biochemical variables were not affected by the treatment. Histopathologic examination of the organs obtained at autopsy did not reveal any alterations. These results support the view that repeated consumption of trans-resveratrol at 20 mg/(kg x d) does not adversely affect the variables tested in rats. (+info)
Effect of inclusion of defatted grape seed meal in the diet on digestion and performance of growing rabbits.
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The digestion and nutritive value of defatted grape seed meal (DGSM) was investigated. A basal diet was formulated to meet requirements of growing rabbits. Another diet was formulated by substituting 15.2% of the basal diet with DGSM. Two hundred eight weaned 30-d-old rabbits were fed these diets, and fattening performance was recorded. Eighty animals were used to study the effect of DGSM inclusion on cecal fermentation traits and intestinal disaccharidase activity at two ages (5 and 35 d after weaning). Fecal apparent digestibility of nutrients was measured in 18 rabbits. A third diet was formulated to contain DGSM (61.3%) as the sole source of fiber and a supplement consisting of wheat flour, casein, lard, and a mixture of vitamins and minerals to avoid nutrient imbalances. This semipurified diet was used to determine cecal digestion traits, disaccharidase activity in the small intestine, fecal apparent digestibility of nutrients, and rate of passage in 70-d-old rabbits. Digestible energy and NDF and CP digestibilities of DGSM calculated by difference were 5.51 +/- 0.89 MJ/kg DM, 24.5 +/- 5.76%, and 46.8 +/- 14.9%, respectively. Inclusion of 15% of DGSM in the basal diet increased ADFI in finishing rabbits (from 9 to 15%; P < 0.05), so that DE intake increased although dietary DE concentration decreased. As a consequence, ADG increased by 3.3% in the whole fattening period (P = 0.046). The increase in ADFI was parallel to an 8% decrease in the weight of cecal contents (P = 0.059), and it was in agreement with the relatively short cecal mean retention time of DGSM (7.61 h) in the semipurified diet. Inclusion of 15% of DGSM in the basal diet did not affect (P > or = 0.20) mortality (10.1%) or cecal concentrations of VFA, NH3 N, or cecal pH either at 5 d (71.9 mM, 17.7 mM, and 5.75, respectively) or at 35 d after weaning (74.6 mM, 10.1 mM, and 5.66, respectively) but improved the sucrase activity in the ileum by 36% (P = 0.031). Digestibility of NDF of DGSM in the semipurified diet was 8.57%, which agrees with the low acidity and weight of cecal contents of animals fed this diet (6.26 and 3.63% BW, respectively). From these results, we conclude that DGSM has a relatively high DE concentration and its inclusion at moderate levels (15%) in the diet exerts a positive effect on ADFI, DE intake, and ADG with no impairment of cecal fermentation and mortality. (+info)