Poster: Membrane Transport

Abs # 1242: Manganese transport in the green microalga C. reinhardtii is mediated by a protein which also enables cadmium import.

Presenter:	Rosakis, Alexandra , alexandra.rosakis@eawag.ch
Authors	Rosakis, Alexandra  (A)   Köster, Wolfgang  (A)
Affiliations:	(A): Environmental Microbiology & Molecular Ecotoxicology, Swiss Federal Institute for Environ. Science & Technology

Little information is available about metal uptake in algae on a molecular level, although these organisms have a significant status in aquatic ecosystems, and can serve as model systems for higher plants. In this study we have cloned from the green microalga Chlamydomonas reinhardtii a gene (named DMT1), which shows high homology to members of the Nramp family. Nramps (natural resistance associated macrophage proteins) form a family of divalent metal ion transporters described in many pro- and eukaryotic organisms. The high degree of conservation on the amino acid level indicates the importance of these proteins for metal homeostasis of the cell. The coding sequence of the cloned DMT1 cDNA codes for a protein with a length of 513 amino acids and 11 putative transmembrane domains. Functional complementation analysis in the yeast S. cerevisiae was chosen as an approach to study DMT1, since directed gene silencing in C. reinhardtii is still a challenging matter. Yeast strains with impaired metal transport systems, revealed that DMT1 from C. reinhardtii is acting efficiently in the transport of manganese. Mutants for zinc and iron transport were not, or partially complemented, respectively. Growth impairment tests showed that cadmium was also imported by DMT1. Characterization of the regulatory features of DMT1 in C. reinhardtii is under way.