Enzymatic antioxidant defences are transcriptionally regulated in Es524, a copper-tolerant strain of Ectocarpus siliculosus (Ectocarpales, Phaeophyceae)

Abstract

Previous investigations have revealed that Ectocarpus siliculosus strain Es524, isolated from a highly copper (Cu)-polluted location in Chile, displays higher activities of the antioxidant enzymes superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT) under Cu excess. This partly explains its enhanced tolerance compared with other E. siliculosus strains. However, the transcriptomic basis behind the activity of these antioxidant enzymes is still unknown. We have conducted laboratory experiments with Es524 under control conditions and exposure to 2.4 μM total Cu. Under Cu exposure, Es524 showed a decrease in cell length and cell plasmolysis, revealing a certain level of cytophysiological stress. The genes encoding for iron-SOD, APX and CAT were overexpressed under Cu excess, demonstrating that higher activities of these enzymes are transcriptionally regulated. It is now more apparent that the induction of SOD, APX and CAT are conserved molecular and biochemical mechanisms developed after a long history of Cu exposure which is responsible, at least in part, for intraspecific Cu tolerance in E. siliculosus.