A novel field transplantation technique reveals intra-specific metal-induced oxidative responses in strains of Ectocarpus siliculosus with different pollution histories

Abstract

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.

MAPK Pathway under Chronic Copper Excess in Green Macroalgae (Chlorophyta): Involvement in the Regulation of Detoxification Mechanisms

“…As in previous investigations [13], U. compressa displayed a higher total glutathione pool under chronic copper excess in relation to controls, although at late exposures (6 d). At 48 h and beyond, patterns of higher GSSG upon GSH were observed in copper-exposed macroalgae, which is coincident with an induction of ROS over-production and GSH oxidation, indeed, a decrease in GSH/GSSG ratios have been recorded in several photoautotrophs under chronic copper excess and is fairly recognised as a good indicator of an oxidative stress condition [2,4,5,23,24]. In the presence of copper and MAPK inhibitors, most consistent trends were observed at 6 d. In most treatments with copper and one or more MAPK blocked pathways, with the exceptions of ERKi + p38i (T7) and JNKi + p38i (T8), GSH levels were always lower than GSSG.…”

“…As a proxy for lipid peroxidation, the levels of thiobarbituric acid reactive substance (TBARS) were measured according to Sáez et al [24]. A total of 100 mg of grounded tissue were lysed with 300 µL of 0.1 % TCA, adding four glass beads (2 mm), and vortexed for 5 min at room temperature.…”

Copper-induced activation of TRPs and VDCCs triggers a calcium signature response regulating gene expression inEctocarpus siliculosus

“…Constant filtered air bubbling was provided to avoid O 2 depletion. The strain Es524 was chosen as is a representative of an E. siliculosus population commonly exposed to copper pollution (see Ritter et al, 2010 ; Sáez et al, 2015a , 2015b , 2015c ); thus, its responses should be able to provide insights on the development of tolerance strategies in brown macroalgae to withstand copper excess in the natural environment.…”

“…E. siliculosus mechanisms to withstand copper excess have been observed to be importantly mediated by cell wall chelation as an exclusion strategy, and the production of intracellular metal-chelating peptides, as glutathione (GSH) and phytochelatins (PCs) ( Roncarati et al, 2015 ). In addition, it has been observed that copper-induced oxidative stress and damage in E. siliculosus is counteracted through the glutathione–ascorbate (Foyer–Halliwell–Asada) cycle, which involves maintaining the equilibrium among reduced and oxidized forms of glutathione (GSH/GSSG) and ascorbate (ASC/DHA/MDHA), and enhanced activities and expression of the enzymes as GR, AP, SOD and catalase (CAT) ( Sáez et al, 2015a , 2015b , 2015c ). It is important to mention that the genome of E. siliculosus has been already published ( Cock et al, 2010 ), providing unprecedented possibilities to deepen on aspects currently unexplored regarding metal-stress metabolism in brown macroalgae; for instance, elucidating the potential involvement of calcium signaling.…”

MAPK Pathway under Chronic Copper Excess in Green Macroalgae (Chlorophyta): Influence on Metal Exclusion/Extrusion Mechanisms and Photosynthesis

“…The biological implications of copper excess are well-documented in photoautotrophs from terrestrial and aquatic ecosystems [11,12,13,14]. Due to domestic and industrial activities, copper is recognized as one of the most pernicious pollutants in the marine environment [15].…”