Transformation of the dinoflagellate chloroplast

Dinoflagellatealgae are ecologically and environmentally important, as symbionts of corals and many other aquatic organisms, and the causative agents of red tides. However, attempts over the last twenty years to establish genetic manipulation systems for dinoflagellateshave met with little success. We have exploited the unusual chloroplastgenome of dinoflagellatesto establish a system for transformation of this organelle. The chloroplastgenome of peridinin-containing (the ancestral state) dinoflagellatesis highly reduced and composed of a number of small, plasmid-like molecules, referred to as ‘ minicircles’. We have constructed shuttle vectorsthat are fusions of minicirclesand Escherichia coli plasmids and carry selectable markers. We used biolistictransformation to introduce these into the model dinoflagellate Amphidinium carterae. We found that the plasmids confer the expected phenotype on the dinoflagellatecells, and we can detect the plasmid DNA and associated transcripts following selection, indicating successful transformation. This opens up the possibility of studying many aspects of dinoflagellate chloroplastbiology, including the maintenance and expression of the minicircles, and the role of the chloroplastin phenomena such as coral bleaching.