Dinophyte chloroplasts and phylogeny - A review

Dinophytes acquired chloroplasts obviously early in evolution and later los t them multiple limes. Most families and genera contain both photosynthetic and heterotrophic species. Chloroplasts enveloped by three membranes with thylakoids in stacks of three, containing peridinin as the main pigment, ar e regarded as the original dinophyte plastids. Pyrenoids are generally pres ent. Stigmata, if present, are usually parts of the chloroplast or are modi fied original plastids. The form II type RUBISCO found in the dinophytes is unique for eukaryotes, otherwise known only in some anaerobic bacteria. It is disputed whether the original dinophyte chloroplasts are derived from a prokaryotic or an eukaryotic endosymbiosis. Various dinoflagellates contai n aberrant chloroplasts. Glenodinium foliaceum and Peridinium balticum have a single complete endosymbiont, originally a pennate diatom. Podolampas bi pes houses several dictyophycean symbiont cells. The "symbionts" of Lepidod inium viride and Gymnodinium chlorophorum are highly reduced prasinophyte c ells. The chloroplasts of Gymnodinium mikimotoi have aberrant pigments (fuc oxanthin derivatives, no peridinin) and fine structure. The dinoflagellate hosts do nor seem to contain any parts of the former endosymbiont except th e chloroplasts. Photosynthetic Dinophysis species have cryptophycean-like c hloroplasts, whereas symbiotic cyanobacteria are found in other members of the Dinophysiales, e.g., Ornithocercus. Various dinophytes, e.g. Gymnodiniu m aeruginosum, use kleptochloroplasts from ingested cryptophytes transientl y for photosynthesis. Original or secondarily acquired chloroplasts can onl y be used for phylogenetic considerations in exceptionally cases: it seems unlikely that the Prorocentrales have evolved from the Dinophysiales becaus e all Prorocentrales possess original dinoflagellate chloroplasts, whereas no member of the Dinophysiales has such chloroplasts.