Purification of plastids from the dinoflagellate Lingulodinium.

Peridinin-containing dinoflagellates are a group of generally marine and photosynthetic protists whose plastids display a number of unusual features. In particular, the plastid genome may be reduced to as few as a dozen genes, and it is not clear if all these genes are expressed. To begin to characterize the plastid proteins, we attempted to purify chloroplasts from the dinoflagellate Lingulodinium polyedrum. We tested several different protocols and found that the organelles were inherently fragile and difficult to isolate intact. In particular, standard purification protocols as described for higher plants produced only broken plastids, as judged by complete loss of the stromal protein RuBisCO. We found that small amounts of RuBisCO could be retained in the plastids if the cells were treated with cellulase prior to lysis. Finally, we report that almost all RuBisCO was retained in plastids prepared from cells subjected to a heat shock treatment, although cellular proteins were denatured by the treatment.