Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0008272 (chlorosis)
 2,195 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In this study, we examined the modulation of Cu toxicity-induced oxidative stress by excess supply of iron in Zea mays L. plants. Plants receiving excess of Cu (100 microM) showed decreased water potential and simultaneously showed wilting in the leaves. Later, the young leaves exhibited chlorosis and necrotic scorching of lamina. Excess of Cu suppressed growth, decreased concentration of chloroplastic pigments and fresh and dry weight of plants. The activities of peroxidase (EC 1.11.1.7; POD), ascorbate peroxidase (EC 1.11.1.11; APX) and superoxide dismutase (EC 1.15.1.1; SOD) were increased in plants supplied excess of Cu. However, activity of catalase (EC 1.11.1.6; CAT), was depressed in these plants. In gel activities of isoforms of POD, APX and SOD also revealed upregulation of these enzymes. Excess (500 microM)-Fe-supplemented Cu-stressed plants, however, looked better in their phenotypic appearance, had increased concentration of chloroplastic pigments, dry weight, and improved leaf tissue water status in comparison to the plants supplied excess of Cu. Moreover, activities of antioxidant enzymes including CAT were further enhanced and thiobarbituric acid reactive substance (TBARS) and H(2)O(2) concentrations decreased in excess-Fe-supplemented Cu-stressed plants. In situ accumulation of H(2)O(2), contrary to that of O(2)(*-) radical, increased in both leaf and roots of excess-Cu-stressed plants, but Cu-excess plants supplied with excess-Fe showed reduced accumulation H(2)O(2) and little higher of O(2)(*-) in comparison to excess-Cu plants. It is, therefore, concluded that excess-Cu (100 microM) induces oxidative stress by increasing production of H(2)O(2) despite of increased antioxidant protection and that the excess-Cu-induced oxidative damage is minimized by excess supply of Fe.
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PMID:Modulation of copper toxicity-induced oxidative damage by excess supply of iron in maize plants. 1789 96

An integrated multilevel phytoassessment of an acid mine drainage (AMD, pH range 3.3-6.8) in southern Portugal was performed. A 7-day phytotoxicity bioassay with the duckweed Lemna gibba (chlorosis, necrosis, growth) was carried out, both in the laboratory and in situ, combined with an analysis of the resident epilithic diatom community. The toxicity test was performed with water from the AMD gradient, an unpolluted river control and acidified control water, in order to discriminate potential pH-effects from combined pH- and metal-effects. Diatom communities discriminated well among the sites (alkalophilic species versus halobiontic, acidobiontic and acidophilic species), showing inter-site differences to be larger than intra-site seasonal variations. In L. gibba exposed to AMD, necrosis and growth inhibition were higher in situ compared to the laboratory experiments. L. gibba was more sensitive to AMD than to acidified water. Already after 4 days, growth rate inhibition in L. gibba proved to be a reliable indicator of AMD-stress. Ecotoxicological thresholds obtained with L. gibba corresponded with those obtained previously with animals of intermediate tolerance to AMD. The results were summarised in a multimetric index.
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PMID:Phytoassessment of acid mine drainage: Lemna gibba bioassay and diatom community structure. 1795 93

Ammonia (i.e. the total of NH(3) and NH(4)(+)) has been one of the main causes of the decline of macrophytes in fresh water. In order to study the effects of ammonia toxicity, plants of the submersed macrophyte Vallisneria natans (Lour.) Hara were treated with various concentrations of NH(4)Cl (0.1, 0.4, 1.2, 2 and 2.8mM) for 4 days or with 2mM NH(4)Cl for different lengths of time (12h, 1, 2, 4 and 8 days). The toxic effect and oxidative stress caused by NH(4)Cl resulted in a reduction of total chlorophyll (chlorophyll a and b) and an increase in the levels of reactive oxygen species (ROS) O(2)(-) and H(2)O(2), with an increased concentration of NH(4)Cl and duration of exposure. Meanwhile, weak chlorosis and water-soaked symptoms were observed in older leaves exposed to 2.8mM NH(4)Cl for 4 days. The activity of superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (POD), ascorbate peroxidase (APX) and glutathione reductase (GR) was up-regulated in leaves treated with 1.2, 2 and 2.8mM NH(4)Cl for 4 days or with 2mM NH(4)Cl for 1, 2 and 4 days, when compared with controls. Among these enzymes, the activity of superoxide dismutase, ascorbate peroxidase and glutathione reductase was significantly up-regulated in plants treated with 0.4mM NH(4)Cl for 4 days, while they were down-regulated at 4 and 8 days from their peak values in leaves treated with 2mM NH(4)Cl. The content of ascorbic acid decreased significantly in leaves treated with 0.4-2.8mM NH(4)Cl for 4 days or with 2mM NH(4)Cl for 2-8 days. The content of total glutathione (tGSH; reduced and oxidized glutathione) increased in leaves treated with NH(4)Cl at 0.4, 1.2 and 2mM for 4 days or with 2mM NH(4)Cl at 1, 2 and 4 days, while tGSH was decreased below the level of controls by treatment with 2.8mM NH(4)Cl for 4 days or to the level of controls by treatment with 2mM NH(4)Cl for 8 days. However, the content of malondialdehyde (MDA) decreased with increased concentration of NH(4)Cl and duration of exposure. Results from staining with 3,3'-dimethoxybenzidine (DAB) further indicated that the level of H(2)O(2) and the activity of guaiacol peroxidase increased significantly in plants exposed to 2mM NH(4)Cl for 4 days. These results suggested that ammonia exerted its toxic effect on the growth of V. natans (Lour.) Hara, at least in part, by induction of oxidative stress and inhibition of photosynthesis. The decrease in the content of malondialdehyde is discussed.
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PMID:Metabolic adaptations to ammonia-induced oxidative stress in leaves of the submerged macrophyte Vallisneria natans (Lour.) Hara. 1830 60

We examined the short-term separate and combined effects of simulated nitrogen (N) deposition (fertilization) and ozone (O(3)) exposure on California black oak seedlings (Quercus kelloggii Newb.), an ecologically important tree of the San Bernardino Mountains downwind of Los Angeles. Realistic concentrations of O(3) were found to cause statistically and biologically significant negative effects on plant health, including lowered photosynthetic ability, lowered water use efficiency, and increased leaf chlorosis and necrosis. When subjected to abrupt changes in light levels, O(3)-exposed plants showed both a slower and smaller response than O(3)-free plants. Fertilized plants exhibited a significantly greater pre- to post-treatment decline in A at saturated [CO(2)] and a significantly lower level of post-treatment chlorosis than unfertilized plants. Fertilization tended to reduce plant sensitivity to O(3).
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PMID:Interactive effects of O3 exposure on California black oak (Quercus kelloggii Newb.) seedlings with and without N amendment. 1831 84

Greenbug, Schizaphis graminum (Rondani) (Hemiptera: Aphididae), was first discovered damaging seashore paspalum (Paspalum vaginatum Swartz) turfgrass in November 2003 at Belle Glade, FL. Inquiries to several golf courses with seashore paspalum turf across southern Florida indicated infestation was wide spread by April 2004. Damage symptoms progress from water soaked lesions surrounding feeding sites within 24 h to chlorosis and necrosis of leaf tips within 96 h. Problems caused by greenbug feeding were initially misdiagnosed as fertilizer, disease, other insects, or water management problems because aphids were not previously found on warm season turfgrasses. Greenbug development and fecundity studies were conducted on six seashore paspalum varieties: 'Aloha,' 'SeaDwarf,' 'SeaGreen,' 'SeaIsle,' 'SeaWay,' and 'SeaWolf.' Greenbug did not survive on 'SeaWolf.' Development rates (mean +/- SEM) ranged from 7.6 +/- 0.2 to 8.2 +/- 0.2 d on the remaining varieties. Greenbug longevity and fecundity on 'Aloha' were significantly less than on the other varieties. The estimated intrinsic rate of natural increase (r(m)) for greenbug ranged from 0.24 to 0.26 across tested varieties. Values for net reproductive rate (R(o)) ranged from 12.3 on 'Aloha' to 40.4 on 'SeaWay.' In feeding trials on indicator plants, the Florida isolate of greenbug exhibited a unique biotypic profile most commonly found on noncultivated grass hosts. It was virulent on the wheat variety GRS1201 that is resistant to the principal agricultural biotypes attacking small grains and to all currently available resistant sorghum varieties.
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PMID:Biology and biotype determination of greenbug, Schizaphis graminum (Hemiptera: Aphididae), on seashore paspalum turfgrass (Paspalum vaginatum). 1841 32

ABSTRACT Disease progress of downy mildew on cucumber leaves, caused by the obligate biotrophic pathogen Pseudoperonospora cubensis, was shown to be associated with various changes in transpiration depending on the stage of pathogenesis. Spatial and temporal changes in the transpiration rate of infected and noninfected cucumber leaves were visualized by digital infrared thermography in combination with measurements of gas exchange as well as microscopic observations of pathogen growth within plant tissue and stomatal aperture during pathogenesis. Transpiration of cucumber leaf tissue was correlated to leaf temperature in a negative linear manner (r = -0.762, P < 0.001, n = 18). Leaf areas colonized by Pseudoperonospora cubensis exhibited a presymptomatic decrease in leaf tem perature up to 0.8 degrees C lower than noninfected tissue due to abnormal stomata opening. The appearance of chlorosis was associated with a cooling effect caused by the loss of integrity of cell membranes leading to a larger amount of apoplastic water in infected tissue. Increased water loss from damaged cells and the inability of infected plant tissue to regulate stomatal opening promoted cell death and desiccation of dying tissue. Ultimately, the lack of natural cooling from necrotic tissue was associated with an increase in leaf temperature. These changes in leaf temperature during downy mildew development resulted in a considerable heterogeneity in temperature distribution of infected leaves. The maximum temperature difference within a thermogram of cucumber leaves allowed the discrimination between healthy and infected leaves before visible symptoms appeared.
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PMID:Effect of downy mildew development on transpiration of cucumber leaves visualized by digital infrared thermography. 1894 15

ABSTRACT Excised leaves of bermudagrass were inoculated with mycelium of isolates of Bipolaris, Exserohilum, Curvularia, and Drechslera spp. in water agar plates to evaluate differences in susceptibility of leaf tissue, virulence of pathogens, and quantitative resistance of bermudagrass genotypes. Isolates of nine species of pathogens induced similar symptoms of light- to dark-brown necrosis and bordering chlorosis in excised leaves that were not distinct for individual species or genera. Severity of symptoms induced by most isolates increased progressively from younger to older leaves. Within and across leaf positions, numerous significant differences in virulence of isolates within fungal species and between species were observed. Among 40 randomly selected bermudagrass genotypes, a continuous quantitative gradient was observed for mean scores of disease severity in excised leaves inoculated with E. rostratum. Numerous significant differences were observed within this gradient, and severity of symptoms in the most susceptible genotypes was approximately double that in the most resistant. When intact foliage of genotypes from the resistant and susceptible extremes of the gradient was inoculated with spores of E. rostratum, corresponding differences in severity of symptoms and significant (P = 0.05) correlations between results with excised leaves and intact foliage were observed. However, the range of differences in disease severity between genotypes was more narrow in intact foliage than in excised leaves. Results indicate that the excised leaf inoculation technique can be used to evaluate the relative resistance of bermudagrass genotypes to E. rostratum for use in programs to breed for quantitative host resistance.
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PMID:An excised-leaf inoculation technique for evaluating host-pathogen interactions and quantitative resistance of bermudagrass genotypes to dematiaceous hyphomycetes. 1894 21

ABSTRACT The addition of 0.1 mM FeCl(3) to a defined culture medium induces the bacterial epiphyte Pseudomonas fluorescens strain A506 (A506) to produce an antibiotic toxic to the fire blight pathogen, Erwinia amylovora. Consequently, because A506 is registered and applied as a commercial product to suppress E. amylovora before floral infection of pear and apple, the relative availability of iron to A506 on surfaces of pear and apple flowers is of potential significance. An 'iron biosensor' construct of A506 was developed by transformation with an iron-regulated promoter (pvd) fused to a promoterless ice nucleation reporter gene (inaZ). This construct, A506 (pvd-inaZ), established high populations on pear and apple flowers, ranging from 10(4) to 10(6) CFU/flower. In seven trials on pear and apple trees, A506 (pvd-inaZ) expressed high ice nucleation activity (INA) on flowers, indicating limited iron bioavailability or a low-iron environment unlikely to induce antibiotic production by A506. A506 (pvd-inaZ) also colonized flowers when mixed with chemicals containing iron: FeSO(4) or the iron chelates ferric ethylenediaminedi-(o-hydroxyphenyl-acetic) acid (FeEDDHA) and ferric diethylenetriamine pentaacetate (FeDTPA). These compounds represent an array of commercial iron formulations applied to foliage to avert iron chlorosis. Treatment of flowers with a mixture of A506 (pvd-inaZ) and 3 mM FeEDDHA or FeDTPA significantly decreased INA compared with flowers treated with A506 (pvd-inaZ) in water. Lower concentrations (0.3 mM) of FeEDDHA, however, did not consistently suppress INA. These results indicate that apple and pear flowers represent an iron-limited environment to A506 and that treatment with 3 mM FeEDDHA is needed to increase significantly the level of iron available to this bacterium.
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PMID:Bioavailability of Iron to Pseudomonas fluorescens Strain A506 on Flowers of Pear and Apple. 1894 98

Spore suspensions of Alternaria brassicae, the causal agent of gray leaf spot in Brassica plants, were incubated on the leaves of cabbage (B. oleracea) and spore germination fluid (SGF) was collected after 48 h. A high molecular weight (HMW) fraction (>10 kDa) was separated from the SGF by ultrafiltration. In a detached leaf assay, the HMW fraction induced visible symptoms only on host leaves and the toxicity was lost by treatment with proteinase K or heat at 60 degrees C for 15 min, indicating the presence of host-specific protein toxin(s). A protein toxin in the HMW fraction was purified by several chromatography steps. The toxin induced water-soaked symptoms followed by chlorosis at concentrations of 0.5 to 1 microg/ml on host leaves, but not on nonhost leaves even at 50 microg/ml. The toxin also had infection-inducing activity when added to spore suspension of a nonpathogenic isolate of A. alternata, causing symptoms similar to the infection of A. brassicae only on host leaves. These results indicate that a new host-specific protein toxin named ABR-toxin is released from germinating spores of A. brassicae on host leaves. ABR-toxin migrated as a protein of 27.5 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The isoelectric point of ABR-toxin was estimated to be approximately 7.0 and 21 N-terminal amino acid residues were sequenced.
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PMID:Alternaria brassicae produces a host-specific protein toxin from germinating spores on host leaves. 1894 95

ABSTRACT Coronatine is a non-host-specific chlorosis-inducing phytotoxin produced by the tomato and crucifer pathogen Pseudomonas syringae pv. tomato DC3000. How the chromosomal gene cluster controlling toxin synthesis in this strain is regulated in planta is unknown. Ice nucleation-active cor:inaZ marker-exchange derivatives of strain DC3000 were used to determine coronatine gene expression in various host and nonhost plants and in a minimal medium supplemented with selected tomato plant constituents. Ice nucleation activity, which was first detected 4 h after inoculation, was highest in cabbage, tomato, and soybean and lowest in melon and cucumber. No correlation existed between bacterial population size and expression level on the various plants. Crude tomato leaf extract and intercellular fluid were strong inducers of toxin synthesis. Based on high-performance liquid chromatography analyses and bioassays, we concluded that the active components of both preparations were malic and citric acids, with minor contributions coming from shikimic and quinic acid. Although several compounds including glucose and inositol activated the toxin genes when tested at high concentrations (3 to 5 mM), shikimic and quinic acids were the only ones with activity at concentrations below 0.1 mM. Neither acid could be used as a sole carbon source by strain DC3000. The signal activity of shikimic acid was enhanced 10-fold by the addition of glucose. None of the plant phenolics that we screened affected coronatine gene expression.
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PMID:Identification of Tomato Leaf Factors that Activate Toxin Gene Expression in Pseudomonas syringae pv. tomato DC3000. 1894 22


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