RESUMEN
Lessonia spicata is a key dominant species along the Pacific coast of South America, providing a habitat for many organisms. However, this role can be affected by abiotic stress, such as metals. To counteract the toxic effect, L. spicata, among other seaweeds, releases exudates that bind metals. In this study, tolerances to copper of organisms related to the kelp forest (spores of Ulva lactuca (Chlorophyceae) and L. spicata (Phaeophyceae) and Zoea I of Taliepus dentatus (Milne-Edwards, Crustacea)) were studied; then, exudates are assessed by their protective effect. Exudates increase the 48-h 50% effective concentration (EC50) of the germination of spores from 8 to 23 µg Cu L-1 for U. lactuca and from 119 to 213 µg Cu L-1 for L. spicata and the survival of the larvae Zoea I 48-h 50% of lethal concentration (LC50) from 144 to 249 µg Cu L-1. Results indicated that exudates had a protective effect. Each species is specifically sensitive to copper. Crab larvae Zoea I were able to support higher doses, and exposure before hatching increased their tolerance.
Asunto(s)
Cobre/toxicidad , Phaeophyceae/efectos de los fármacos , Animales , Braquiuros/efectos de los fármacos , Larva/efectos de los fármacos , Contaminantes Químicos del Agua/toxicidadRESUMEN
A novel field transplantation technique, in which seaweed material is incorporated into dialysis tubing, was used to investigate intra-specific responses to metals in the model brown alga Ectocarpus siliculosus. Metal accumulation in the two strains was similar, with higher concentrations in material deployed to the metal-contaminated site (Ventanas, Chile) than the pristine site (Quintay, Chile). However, the oxidative responses differed. At Ventanas, strain Es147 (from low-polluted site) underwent oxidative damage whereas Es524 (from highly polluted site) was not affected. Concentrations of reduced ascorbate (ASC) and reduced glutathione (GSH) were significantly higher in Es524. Activities of the antioxidant enzymes superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), and glutathione reductase (GR) all increased in Es524, whereas only SOD increased in Es147. For the first time, employing a field transplantation technique, we provide unambiguous evidence of inter-population variation of metal-tolerance in brown algae and establish that antioxidant defences are, in part, responsible.
Asunto(s)
Monitoreo del Ambiente/métodos , Contaminación Ambiental/estadística & datos numéricos , Metales/toxicidad , Phaeophyceae/fisiología , Contaminantes Químicos del Agua/toxicidad , Ascorbato Peroxidasas/metabolismo , Catalasa/metabolismo , Chile , Glutatión/metabolismo , Glutatión Reductasa/metabolismo , Oxidación-Reducción , Phaeophyceae/efectos de los fármacos , Algas Marinas/metabolismo , Superóxido Dismutasa/metabolismoRESUMEN
Inter- and intra-specific variation in metal resistance has been observed in the ecologically and economically important marine brown macroalgae (Phaeophyceae), but the mechanisms of cellular tolerance are not well elucidated. To investigate inter-population responses of brown seaweeds to copper (Cu) pollution, the extent of oxidative damage and antioxidant responses were compared in three strains of the filamentous brown seaweed Ectocarpus siliculosus, the model organism for the algal class Phaeophyceae that diverged from other major eukaryotic groups over a billion year ago. Strains isolated from locations with different pollution histories (i.e. LIA, from a pristine site in Scotland; REP and Es524 from Cu-contaminated sites in England and Chile, respectively) were exposed to total dissolved Cu concentrations (CuT) of up to 2.4 µM (equivalent to 128 nM Cu(2+)) for 10 d. LIA exhibited oxidative stress, with increases in hydrogen peroxide (H2O2) and lipid peroxidation (measured as TBARS levels), and decreased concentrations of photosynthetic pigments. Es524 presented no apparent oxidative damage whereas in REP, TBARS increased, revealing some level of oxidative damage. Adjustments to activities of enzymes and antioxidant compounds concentrations in Es524 and REP were strain and treatment dependent. Mitigation of oxidative stress in Es524 was by increased activities of superoxide dismutases (SOD) at low CuT, and catalase (CAT) and ascorbate peroxidase (APX) at all CuT, accompanied by higher levels of antioxidants (ascorbate, glutathione, phenolics) at higher CuT. In REP, only APX activity increased, as did the antioxidants. For the first time evidence is presented for distinctive oxidative stress defences under excess Cu in two populations of a species of brown seaweed from environments contaminated by Cu.
Asunto(s)
Cobre/toxicidad , Peroxidación de Lípido/efectos de los fármacos , Estrés Oxidativo/efectos de los fármacos , Phaeophyceae/efectos de los fármacos , Contaminantes Químicos del Agua/toxicidad , Inglaterra , Exposición a Riesgos Ambientales , Activación Enzimática/efectos de los fármacos , Peróxido de Hidrógeno/análisis , Oxidación-Reducción/efectos de los fármacos , Oxidorreductasas/metabolismoRESUMEN
Some populations of brown seaweed species inhabit metal-polluted environments and can develop tolerance to metal stress, but the mechanisms by which this is accomplished are still to be elucidated. To address this, the responses of two strains of the model brown alga Ectocarpus siliculosus isolated from sites with different histories of metal contamination exposed to total copper (CuT) concentrations ranging between 0 and 2.4 µM for 10 days were investigated. The synthesis of the metal-chelator phytochelatin (PCs) and relative levels of transcripts encoding the enzymes γ-glutamylcysteine synthetase (γ-GCS), glutathione synthase (GS) and phytochelatin synthase (PCS) that participate in the PC biosynthetic pathway were measured, along with the effects on growth, and adsorption and uptake of Cu. Growth of strain LIA, from a pristine site in Scotland, was inhibited to a greater extent, and at lower concentrations, than that of Es524, isolated from a Cu-contaminated site in Chile. Concentrations of intra-cellular Cu were higher and the exchangeable fraction was lower in LIA than Es524, especially at the highest exposure levels. Total glutathione concentrations increased in both strains with Cu exposure, whereas total PCs levels were higher in Es524 than LIA; PC2 and PC3 were detected in Es524 but PC2 only was found in LIA. The greater production and levels of polymerisation of PCs in Es524 can be explained by the up-regulation of genes encoding for key enzymes involved in the synthesis of PCs. In Es524 there was an increase in the transcripts of γ-GCS, GS and PCS, particularly under high Cu exposure, whereas in LIA4 transcripts of γ-GCS1 increased only slightly, γ-GCS2 and GS decreased and PCS did not change. The consequences of higher intra-cellular concentrations of Cu, lower production of PCs, and lower expression of enzymes involved in GSH-PCs synthesis may be contributing to an induced oxidative stress condition in LIA, which explains, at least in part, the observed sensitivity of LIA to Cu. Therefore, responses to Cu exposure in E. siliculosus relate to the contamination histories of the locations from where the strains were isolated and differences in Cu exclusion and PCs production are in part responsible for the development of intra-specific resistance.
Asunto(s)
Vías Biosintéticas/efectos de los fármacos , Cobre/toxicidad , Regulación Enzimológica de la Expresión Génica/efectos de los fármacos , Phaeophyceae/efectos de los fármacos , Fitoquelatinas/genética , Contaminantes Químicos del Agua/toxicidad , Aminoaciltransferasas/genética , Aminoaciltransferasas/metabolismo , Chile , Cobre/análisis , Glutamato-Cisteína Ligasa/genética , Glutamato-Cisteína Ligasa/metabolismo , Glutatión/metabolismo , Phaeophyceae/química , Fitoquelatinas/metabolismo , Especificidad de la EspecieRESUMEN
Brown algae are often used as heavy metal biomonitors and biosorbents because they can accumulate high concentrations of metals. Cation-exchange performed by cell wall polysaccharides is pointed out as the main chemical mechanism for the metal sequestration. Here, we biochemically investigated if the brown alga Padina gymnospora living in a heavy metal contaminated area would modify their polysaccharidic content. We exposed non-living biomass to Cd and Pb and studied the metals adsorption and localization. We found that raw dried polysaccharides, sulfate groups, uronic acids, fucose, mannose, and galactose were significantly higher in contaminated algae compared with the control ones. Metal concentrations adsorbed by non-living biomass were rising comparatively to the tested concentrations. Electron microscopy showed numerous granules in the cell walls and X-ray microanalysis revealed Cd as the main element. We concluded that P. gymnospora overproduces cell wall polysaccharides when exposed to high metal concentrations as a defense mechanism.
Asunto(s)
Cadmio/toxicidad , Plomo/toxicidad , Phaeophyceae/efectos de los fármacos , Polisacáridos/biosíntesis , Contaminantes Químicos del Agua/toxicidad , Pared Celular/efectos de los fármacos , Pared Celular/metabolismo , Pared Celular/ultraestructura , Phaeophyceae/metabolismo , Phaeophyceae/ultraestructuraRESUMEN
A proteomic analysis combining peptide de novo sequencing and BLAST analysis was used to identify novel proteins involved in copper tolerance in the marine alga Scytosiphon gracilis (Phaeophyceae). Algal material was cultivated in seawater without copper (control) or supplemented with 100 microg L(-1) for 4 days, and protein extracts were separated by two-dimensional gel electrophoresis (2-DE). From the proteins obtained in the copper treatment, 25 over-expressed, 5 under-expressed and 5 proteins with no changes as compared with the control, were selected for sequencing. Tryptic-peptides obtained from 35 spots were analyzed by capillary liquid chromatography and tandem mass spectroscopy (capLC/MS/MS), and protein identity was determined by BLASTP. We identified 19 over-expressed proteins, including a chloroplast peroxiredoxin, a cytosolic phosphomannomutase, a cytosolic glyceraldehyde-3-phosphate dehydrogenase, 3 ABC transporters, a chaperonine, a subunit of the proteasome and a tRNA synthase, among others. The possible involvement of these over-expressed proteins in buffering oxidative stress and avoiding metal uptake in S. gracilis exposed to copper excess is discussed taking into consideration the information available for other plant models.