Phylogenetic evidence for the cryptophyte origin of the plastid of Dinophysis (Dinophysiales, Dinophyceae)

Photosynthetic members of the genus Dinophysis Ehrenberg contain a plastid of uncertain origin. Ultrastructure and pigment analyses suggest that the two-membrane-bound plastid of Dinophysis spp. has been acquired through endosymbiosis from a cryptophyte. However, these organisms do not survive in culture, raising the possibility that Dinophysis spp. have a transient kleptoplast. To test the origin and permanence of the plastid of Dinophysis , we sequenced plastid-encoded psb A and small subunit rDNA from single-cell isolates of D. acuminata Claparede et Lachman, D. acuta Ehrenberg, and D. norvegica Claparede et Lachman. Phylogenetic analyses confirm the cryptophyte origin of the plastid. Plastid sequences from different populations isolated at different times are monophyletic with robust support and show limited polymorphism. DNA sequencing also revealed plastid sequences of florideophyte origin, indicating that Dinophysis may be feeding on red algae.