Trace metal economy in Chlamydomonas

School Colloquium

Inorganic trace elements can limit the abundance of photosynthetic organisms because of their role as cofactors in enzymes. In Chlamydomonas cultures placed in a situation of poor copper nutrition, copper is preferentially allocated to cytochrome oxidase over ferroxidase and plastocyanin. In a pathway controlled by a copper-sensing transcription factor, plastocyanin, functionally replaced by cytochrome c₆, is degraded and its copper cofactor is recycled for continued synthesis of cytochrome oxidase, an essential enzyme in respiration. RNA-seq analysis of the Chlamydomonas transcriptome in batch culture of copper-deficient cells identifies a candidate protease for plastocyanin degradation. The co-occurrence of genetic information for plastocyanin as well as functionally-equivalent cytochrome c₆ in algal and cyanobacterial genomes suggests a role for plastocyanin in copper sequestration, which may provide a competitive advantage in copper-deplete environments.

For more information contact Prof. Christoph Fahrni (404-385-1164).