Formation of long-wavelength chlorophyllide (Chlide695) is required for the assembly of Photosystem II in etiolated barley leaves

Chlorophyll(ide) spectroscopic properties and Photosystem II assembly, monitored by 77 K variable fluorescence, were studied in etiolated barley leaves as a function of the extent of protochlorophyllide photoreduction by a single millisecond light flash of different intensities. Variable fluorescence, measured 2 hours after the flash, was only detected when the extent of phototransformation was higher than a threshold value of 0.4. Its development paralleled the formation of a chlorophyll emission component at 685 nm, which itself derived from long-wavelength chlorophyllide with an emission maximum at 695 nm. At low flash intensities, short-wavelength chlorophyllide forms preferentially accumulated and no Photosystem II fluorescence was detected after 2 hours. Chlorophyllide esterification was independent of the extent of phototransformation. These results suggested that the formation of long-wavelength chlorophyllide was essential for further assembly of Photosystem II. This interpretation was strengthened by the observed inhibition of both long-wavelength chlorophyllide formation and of variable fluorescence development in leaves treated with 6-aminolevulinic acid or in untreated leaves subjected to repeated flashes of low intensity

Polychaetes as Bioindicators of Water Quality in the Saguenay Fjord (Quebec, Canada): A Preliminary Investigation

The Saguenay Fjord, a key affluent of the St-Lawrence River estuary (SLRE), is prone to environmental pressures stemming from mixed and diffuse sources of (in)organic contamination, and has been studied extensively with bivalves as indicators of water quality. [...

Ecotoxicity of selected pharmaceuticals of urban origin discharged to the Saint-Lawrence river (Québec, Canada): a review.

Twelve pharmaceuticals comprising anti-inflammatory agents (ibuprofen, naproxen), lipid regulators (bezafibrate, gemfibrozil), an anti-convulsant (carbamazepine), antibiotics (sulfamethoxazole, sulfapyridine, oxytetracycline, novobiocin, trimethoprim), a stimulant (caffeine) and a nicotine metabolite (cotinine) were identified in the final effluent of a major wastewater treatment plant (WWTP) based in the Montreal area (Québec, Canada) discharging to the Saint-Lawrence River. Their measured concentrations ranged from 33 (carbamazepine) to 22187 ng/L (caffeine) in the Montreal WWTP effluent and from 58 (cotinine) to 85000 (ibuprofen) ng/L based on maximum concentrations found in other municipal effluents as reported elsewhere. In general, elimination of these drugs by wastewater treatment is purported to be fairly efficient for ibuprofen, naproxen, bezafibrate, gemfibrozil and caffeine. In contrast, carbamazepine, sulfamethoxazole, sulfapyridine and oxytetracycline appear more resistant to treatment whereas removal efficiency for novobiocin, trimethoprim and cotinine is either unclear or unknown. Despite the degree to which they are eliminated in WWTps, their presence in urban effluents discharging to surface waters is common. To estimate their potential risk to aquatic biota, we undertook acute/chronic toxicity testing with a suite of small-scale bioassays representing four taxonomic groups (bacteria, algae, invertebrates and fish) and complemented our results with those published in the literature. When all acute and chronic toxicity tests were combined, their toxicity responses spanned over five orders of magnitude. Barring caffeine and cotinine, all others are clearly recognized as toxic based on the EU-Directive 93/67/EEC classification, but their concentrations measured in WTTPs are too low to cause acute or chronic effects on an individual basis. Sulfamethoxazole, naproxen and ibuprofen, however, were found to produce toxic effects at concentrations that areTwelve pharmaceuticals comprising anti-inflammatory agents (ibuprofen, naproxen), lipid regulators (bezafibrate, gemfibrozil), an anti-convulsant (carbamazepine), antibiotics (sulfamethoxazole, sulfapyridine, oxytetracycline, novobiocin, trimethoprim), a stimulant (caffeine) and a nicotine metabolite (cotinine) were identified in the final effluent of a major wastewater treatment plant (WWTP) based in the Montreal area (Québec, Canada) discharging to the Saint-Lawrence River. Their measured concentrations ranged from 33 (carbamazepine) to 22187 ng/L (caffeine) in the Montreal WWTP effluent and from 58 (cotinine) to 85000 (ibuprofen) ng/L based on maximum concentrations found in other municipal effluents as reported elsewhere. In general, elimination of these drugs by wastewater treatment is purported to be fairly efficient for ibuprofen, naproxen, bezafibrate, gemfibrozil and caffeine. In contrast, carbamazepine, sulfamethoxazole, sulfapyridine and oxytetracycline appear more resistant to treatment whereas removal efficiency for novobiocin, trimethoprim and cotinine is either unclear or unknown. Despite the degree to which they are eliminated in WWTps, their presence in urban effluents discharging to surface waters is common. To estimate their potential risk to aquatic biota, we undertook acute/chronic toxicity testing with a suite of small-scale bioassays representing four taxonomic groups (bacteria, algae, invertebrates and fish) and complemented our results with those published in the literature. When all acute and chronic toxicity tests were combined, their toxicity responses spanned over five orders of magnitude. Barring caffeine and cotinine, all others are clearly recognized as toxic based on the EU-Directive 93/67/EEC classification, but their concentrations measured in WTTPs are too low to cause acute or chronic effects on an individual basis. Sulfamethoxazole, naproxen and ibuprofen, however, were found to produce toxic effects at concentrations that ar

Enzymatic basis for fungicide removal by <em>Elodea canadensis</em>.

Purpose Plants can absorb a diversity of natural and man-made toxic compounds for which they have developed diverse detoxification mechanisms. Plants are able to metabolize and detoxify a wide array of xenobiotics by oxidation, sugar conjugation, glutathione conjugation, and more complex reactions. In this study, detoxification mechanisms of dimethomorph, a fungicide currently found in aquatic media were investigated in Elodea canadensis. Methods Cytochrome P450 (P450) activity was measured by an oxygen biosensor system, glucosyltransferases (GTs) by HPLC, glutathione S-transferases (GSTs), and ascorbate peroxidase (APOX) were assayed spectrophotometrically.Results Incubation of Elodea with dimethomorph induced an increase of the P450 activity. GST activity was not stimulated by dimethomorph suggesting that GST does not participate in dimethomorph detoxification. In plants exposed to dimethomorph, comparable responses were observed for GST and APOX activities showing that the GST was more likely to play a role in response to oxidative stress. Preincubation with dimethomorph induced a high activity of O- and N-GT, it is therefore likely that both enzymes participate in the phase II (conjugation) of dimethomorph detoxification process. Conclusions For the first time in aquatic plants, P450 activity was shown to be induced by a fungicide suggesting a role in the metabolization of dimethomorph. Moreover, our finding is the first evidence of dimethomorph and isoproturon activation of cytochrome P450 multienzyme family in an aquatic plant, i.e., Elodea (isoproturon was taken here as a reference molecule). The detoxification of dimetomorph seems to proceed via hydroxylation, and subsequent glucosylation, and might yield soluble as well as cell wall bound residues

Potential use of Lemna minor for the phytoremediation of isoproturon and glyphosate.

International audienc

Changes of chlorophyll(ide) fluorescence yield induced by a short light pulse as a probe to monitor the early steps of etioplast phototransformation in dark-grown leaves

The fluorescence yield of chlorophyll(ide) (ChI[ide]) excited by weak modulated light was recorded at room temperature during a 2 h period after a short actinic light pulse that transformed all photoactive protochlorophyllide in dark-grown barley leaves. A typical pattern of fluorescence yield variations was found whatever the age of the leaf but with age-dependent changes in rates. Its successive phases were related to the Chl(ide) spectral shifts observed in low-temperature emission spectra. The fluorescence yield started at a high level and strongly declined during the formation of Chlide(695) from Chlide(688) within a few seconds. It increased to a transient maximum during the Shibata shift (15-25 min) that resulted in ChI(ide)(682). A final, slow decrease to a steady state occurred during the final red shift to ChI(685). Pretreatments with delta-aminolevulinic acid, chloramphenicol or 1,10-phenanthroline resulted in correlated modifications of Chl(ide) fluorescence yield transients and shifts of the low-temperature Chl(ide) emission band. The complex response of the final decrease phase of the fluorescence yield to these compounds suggests that it results both from the assembly of photosynthetic Chi proteins and from the reorganization of the etioplast membrane system. From these results it is concluded that continuous recordings of CN(ide) fluorescence yield after a short light pulse represent a useful tool to monitor the kinetics of pigment-protein organization and primary thylakoid assembly triggered by Pchlide photoreduction