Electroporation transformation of FITC-dextran into Oxyrrhis marina - an early branching dinoflagellate. v3

INTRODUCTION Here we describe a protocol for transforming Oxyrrhis marina with FITC-labelled dextran (a DNA analog) by electroporation. This protocol is reproducible, and results in a transformation efficiency of around 1%. We have confirmed the viability of transformed cells by allowing them to recover in the dark (and thus maintain fluorescence intensity) and then by observing fluorescent cells swimming normally, days after transformation (see the videohere). NOTE ON AUTOFLUORESCENCE Although Oxyrrhis is a non-photosynthetic dinoflagellate and therefore lacks plastid autofluorescence, we have observed a small amount of green autofluorescence that is typically isolated in the anterior of the cell (See top panel of Figure 1). The autofluorescence was observed in wildtype cells, cells electroporated without FITC-dextran, and cells that were incubated with FITC-dextran but not electroporated. The autofluorescence was observed in cultures with both Dunaliella tertiolecta or heat-killed E. coli. The brightness and frequency of the autofluorescence also seemed to be dependent on culture conditions. Not all cells had the autofluorescence. ADDITIONAL INFORMATION As of yet we have been unable to demonstrate the actual uptake of plasmid DNA. We have tried using rhodamine labelled plasmids to demonstrate this but the results were inconclusive due to issues with cellular autofluorescence. We have also tried this method with a variety of expression plasmidsencoding different promoters. For example, we tried the MOE promoter fromPerkinsus marinus(a closely related species) and the generic eukaryotic CMV promoter. However no GFP fluorescence was detected in these samples. We have also tried transformingin vitro synthesized GFP encoding mRNA using this protocol. As of yet, no GFP production has been detected, but this may reflect non-cannonical translational systems in dinoflagellates as the same mRNA could be translated in starfish embryos. Although the development of expression systems in dinoflagellates remains a challenge, our results suggest thatO. marina may be amenable to genetic transformation.