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Paralytic shellfish toxins inhibit copper uptake in Chlamydomonas reinhardtii
Author(s) -
Cusick Kathleen D.,
Wetzel Randall K.,
Minkin Steven C.,
Dodani Sheel C.,
Wilhelm Steven W.,
Sayler Gary S.
Publication year - 2013
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.2187
Subject(s) - saxitoxin , chlamydomonas reinhardtii , cyanobacteria , paralytic shellfish poisoning , biology , toxin , algae , algal bloom , shellfish poisoning , phytoplankton , environmental chemistry , biochemistry , chemistry , botany , shellfish , ecology , gene , aquatic animal , bacteria , fishery , genetics , nutrient , mutant , fish <actinopterygii>
Paralytic shellfish toxins are secondary metabolites produced by several species of dinoflagellates and cyanobacteria. Known targets of these toxins, which typically occur at detrimental concentrations during harmful algal blooms, include voltage‐gated ion channels in humans and other mammals. However, the effects of the toxins on the co‐occurring phytoplankton community remain unknown. The present study examined the molecular mechanisms of the model photosynthetic alga Chlamydomonas reinhardtii in response to saxitoxin exposure as a means of gaining insight into the phytoplankton community response to a bloom. Previous work with yeast indicated that saxitoxin inhibited copper uptake, so experiments were designed to examine whether saxitoxin exhibited a similar mode of action in algae. Expression profiling following exposure to saxitoxin or a copper chelator produced similar profiles in copper homeostasis genes, notably induction of the cytochrome c 6 ( CYC6 ) and copper transporter ( COPT1 , CTR1 ) genes. Cytochrome c 6 is used as an alternative to plastocyanin under conditions of copper deficiency, and immunofluorescence data showed this protein to be present in a significantly greater proportion of saxitoxin‐exposed cells compared to controls. Live‐cell imaging with a copper‐sensor probe for intracellular labile Cu(I) confirmed that saxitoxin blocked copper uptake. Extrapolations of these data to phytoplankton metabolic processes along with the copper transporter as a molecular target of saxitoxin based on existing structural models are discussed. Environ Toxicol Chem 2013;32:1388–1395. © 2013 SETAC