Copper-induced synthesis of ascorbate, glutathione and phytochelatins in the marine alga Ulva compressa (Chlorophyta)

Copper-induced overexpression of genes encoding antioxidant system enzymes and metallothioneins involve the activation of CaMs, CDPKs and MEK1/2 in the marine alga Ulva compressa

“…In contrast, although we observed an increase in the level of gr transcripts at day 3, our past investigations in U. compressa under 10 µM copper for 7 days have shown that total GR activity increases at day 1 (González et al 2010); the latter may be due to the fact that in this work we only detected the level of transcripts encoding a chloroplast isoform of GR, and not the cytosolic and mitochondrial GR isoforms, which could have a more relevant role mediating total GR activity. On the other hand, transcripts encoding enzymes involved in ASC and GSH syntheses increased until day 12 which is in accord with the increase in activities of L-GDH and L-GLDH and γ-GCL and GS activities that were recorded to increase until day 7 in the alga cultivated with 10 µM copper (Mellado et al 2012). Interestingly, the increase in the level of transcripts encoding antioxidant enzymes and enzymes involved in ASC and GSH syntheses was relatively similar, of around 15 to 20-fold, which suggests that increase in the level of transcripts encoding enzymes of the antioxidant system is, at some extent, a coordinated process in U.…”

“…Samples were then cultivated with 10 µM copper for 3 days, in order to analyze the level of transcripts encoding γ-GCL, L-GLDH and MT1, and for 7 days in order to detect the level of transcripts encoding AP, DHAR, GR, L-GDH, GS and MT2 to MT7. Previous experiments have shown that inhibitors decreased transcript levels after 3 days of culture (González et al 2012); considering that transcripts are still inhibited at 7 days of culture, it indicates that inhibitors are probably being slowly metabolized. Indeed, U. compressa presented slow physiological responses compared to animals, as in the case of intracellular calcium increase involving VoltageDependent Calcium Channels (VDCC) that occurred at 2, 3 and 12 h after copper exposure.…”

“…compressa was incubated with 50 µM W-7, an inhibitor of calmodulins (CaMs), with 5 µM staurosporine (stau), an inhibitor of calcium-dependent protein kinases (CDPKs), and with 5 µM PD98059, an inhibitor of MEK1/2, for 10 min. It is important to mention that, after 3 days of culture with 10 μM copper, the algae incubated for 10-20 min with 100 μM W-7 or with 10 μM stau showed a decrease in transcripts encoding antioxidant enzymes and a MT compared to controls (González et al, 2012), indicating that the inhibitory effect of W-7 and stau persist at least within 3 days. In addition, concentrations of W-7 and stau were similar to those used in animal cells, and PD 98059 was used at 5 μM since its IC50 was 2-7 μM.…”

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

“…These findings imply that the bioavailability of Cu and other metals to E. siliculosus at Ventanas is greater than in our Cu-exposure laboratory experiments and is having a distinct impact on ROS over-production which is apparently counteracted by ascorbate metabolism. Similar results, of marked increases in DHA under metal excess, have been found for L. nigrescens and S. lomentaria (Contreras et al, 2009(Contreras et al, , 2005 and U. compressa (Mellado et al, 2012;Ratkevicius et al, 2003). Thus, at , and the metal-polluted location Ventanas (black bars), in central Chile.…”

“…For example, Nielsen et al (2003) observed that growth rates of embryos and adults of Fucus serratus from a metal polluted location were significantly higher than those from a pristine location, when exposed up to 2 mmol L À1 Cu in vitro. Although the mechanisms of tolerance have not been fully elucidated, there is evidence that the foundation for inter-and intra-specific variation in tolerance is a combination of efficient cell exclusion, synthesis of metal-chelating compounds and activation of reactive oxygen metabolism (Contreras et al, 2009;Gledhill et al, 1999;Gonz alez et al, 2010;Mellado et al, 2012;Pawlik-Skowronska et al, 2007). Most of what is known about metal-mediated responses in seaweeds has been derived from experimentation under controlled conditions in the laboratory, but, despite these data being invaluable, they may not necessarily explain what is happening in the more complex natural environment.…”