Browsing by Author "Contreras, Loretto"

Now showing 1 - 8 of 8
  • No Thumbnail Available
    Item
    Effects of copper on early developmental stages of Lessonia nigrescens Bory (Phaeophyceae)
    (2007) Contreras, Loretto; Medina, Matias H.; Andrade, Santiago; Oppliger, Valeria; Correa, Juan A.
    Copper effects on the early developmental gametophytic and sporophytic stages of the kelp Lessonia nigrescens were tested in gradients of increasing concentrations of ASV-Iabile copper. The results demonstrated a high sensitivity to copper of all life-history stages of the alga, where even the lowest tested concentration affected spore release as well as their subsequent settlement. More significant, concentrations higher than 7.87 mu g L-1 totally interrupted the development of the spores after they settle. This effect led to a failure in the formation of male and female ametophytes and, as a consequence, to a complete disruption of the normal life cycle of the kelp. Thus, we suggest that the absence of L. nigrescens from copper-enriched environments results from the high sensitivity of its early life cycle stages, which limits growth and maturation of the gametophytic microscopic phase and, as a consequence, prevents development of the macroscopic sporophytic phase. (c) 2006 Elsevier Ltd. All rights reserved.
  • Thumbnail Image
    Item
  • No Thumbnail Available
    Item
    Experimental transplants of the large kelp Lessonia nigrescens (Phaeophyceae) in high-energy wave exposed rocky intertidal habitats of northern Chile
    (2006) Correa, Juan A.; Lagos, Nelson A.; Medina, Matias H.; Castilla, Juan C.; Cerda, Mauricio; Ramirez, Marco; Martinez, Enrique; Faugeron, Sylvain; Andrade, Santiago; Pinto, Raquel; Contreras, Loretto
    Potential for addressing ecological and physiological issues becomes severely limited when the organisms required to experimentally test specific hypotheses are absent from the study areas. This report describes a simple and inexpensive device for re-planting kelps into the lower intertidal zone of wave-swept rocky habitats, using Lessonia nigrescens Bory as a model organism. The device allows a wide range of plant sizes to be anchored by the holdfast. Transplanted kelps regenerated, re-attached to the substratum and overgrew the transplanting device. These results confirm the feasibility of using this technique to tackle a variety of highly relevant questions involving ecological, physiological, conservation, restoration and management issues. (c) 2006 Elsevier B.V. All rights reserved.
  • No Thumbnail Available
    Item
    Kinetics of copper accumulation in Lessonia nigrescens (Phaeophyceae) under conditions of environmental oxidative stress
    (2006) Andrade, Santiago; Contreras, Loretto; Moffett, James W.; Correa, Juan A.
    Juvenile individuals of the brown kelp Lessonia nigrescens were exposed to a coastal environment chronically impacted by copper mine wastes and currently displaying more than 250 nM of total dissolved copper. The kinetic of copper accumulation in the intra and extracellular compartments was determined and correlated to the oxidative burst resulting from copper-mediated oxidative stress. Accumulation involved an initial adsorption onto the outer cell wall followed by a slower uptake into the cells. A linear pattern of copper uptake over time was found during the first 52 h of exposure, and a steady state was reached at 76 h. The resulting oxidative stress was found to be inefficiently attenuated, and the intracellular level of copper remained sufficiently high to determine a persistently higher than normal level of reactive oxygen species (ROS). Thus, our results strongly suggest that, in L. nigrescens, copper needs to reach an intracellular threshold before oxidative burst develops. Furthermore, it was found that the high ROS levels generated by copper accumulation within the cells persists after the oxidative burst has ceased, suggesting a limited capacity of the algal tissue to buffer the increases of ROS caused by the environmental copper levels. (c) 2006 Elsevier B.V. All rights reserved.
  • Thumbnail Image
    Item
    Kinetics of Copper Accumulation in Lessonia Nigrescens (Phaeophyceae) Under Conditions of Environmental Oxidative Stress
    (2006) Andrade, Santiago ; Contreras, Loretto; Moffett, James W.; Correa M., Juan A.
  • No Thumbnail Available
    Item
    LUIGI PROVASOLI AWARD RECIPIENTS
    (2009) Thomas, Daniela; Beltran, Jessica; Flores, Veronica; Contreras, Loretto; Bollmann, Edda; Correa, Juan A.
    As part of a long-term study on the biology and ecology of the intertidal kelp Lessonia nigrescens Bory, we report on the occurrence of gall development on this alga, identified the possible causal agent, and assessed the extent of the phenomenon in two wild stands of the host. Our results showed that galls affecting natural populations of L. nigrescens were associated with the infection by a filamentous brown algal endophyte of the genus Laminariocolax. Assignment to Laminariocolax of the endophytes isolated from cultured gall tissue was based on the (i)high internal transcribed spacer 1 (ITS1) sequence similarity and phylogenetic relationship between the Chilean isolates and several species of the genus Laminariocolax endophytic in other kelps, (ii) reproductive and vegetative features of the endophyte in culture, and (iii) anatomical agreement of fully developed galls of Lessonia with those described for other kelp galls caused by endophytic members of Laminariocolax. Unequivocal identification at the species level of the endophytes infecting Lessonia, however, awaits further studies.
  • Thumbnail Image
    Item
    Molecular and morphologically distinct Scytosiphon species (Scytosiphonales, Phaeophyceae) display similar antioxidant capacities
    (2007) Contreras, Loretto; Palma Vásquez, Ramón Eduardo; Correa M., Juan A.
  • No Thumbnail Available
    Item
    Proteomic analysis and identification of copper stress-regulated proteins in the marine alga Scytosiphon gracilis (Phaeophyceae)
    (2010) Contreras, Loretto; Moenne, Alejandra; Gaillard, Fanny; Potin, Philippe; Correa, Juan A.
    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 mu g 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. (C) 2009 Elsevier B.V. All rights reserved.