DINOPHYSIS CAUDATA (DINOPHYCEAE) SEQUESTERS AND RETAINS PLASTIDS FROM THE MIXOTROPHIC CILIATE PREY MESODINIUM RUBRUM¹

Abstract

"Phototrophic"Dinophysis Ehrenberg species are well known to have chloroplasts of a cryptophyte origin, more specifically of the cryptophyte genus complex Teleaulax/Geminigera. Nonetheless, whether chloroplasts of "phototrophic"Dinophysis are permanent plastids or periodically derived kleptoplastids (stolen chloroplasts) has not been confirmed. Indeed, molecular sequence data and ultrastructural data lead to contradictory interpretations about the status of Dinophysis plastids. Here, we used established cultures of D. caudata strain DC-LOHABE01 and M. rubrum strain MR-MAL01 to address the status of Dinophysis plastids. Our approach was to experimentally generate D. caudata with "green" plastids and then follow the ingestion and fate of "reddish-brown" prey plastids using light microscopy, time-lapse videography, and single-cell TEM. Our results for D. caudata resolve the apparent discrepancy between morphological and molecular data by showing that plastids acquired when feeding on M. rubrum are structurally modified and retained as stellate compound chloroplasts characteristic of Dinophysis species.

Morphological Transition in Kleptochloroplasts after Ingestion in the Dinoflagellates Amphidinium poecilochroum and Gymnodinium aeruginosum (Dinophyceae)

“…In the case of Dinophysis caudata, kleptochloroplasts make their way into the dinoflagellate cytoplasm via the food vacuoles, and then elongate toward the periphery of the cell. At the same time, the kleptochloroplasts are highly modified not only with regard to their shape but also with regard to the arrangement of the thylakoids relative to the pyrenoid (Kim et al 2012). As in H. arenicola and D. caudata, the kleptochloroplast of Amphidinium poecilochroum and Gymnodinium aeruginosum also become highly modified under experimental conditions.…”

“…The kleptochloroplasts lie directly in the dinoflagellate cytoplasm, and not in the food vacuole . Recently, the process of kleptochloroplast isolation in D. caudata was revealed ultrastructurally (Kim et al 2012). The study showed that D. caudata takes up kleptochloroplasts together with other organelles of M. rubrum into a food vacuole, and then isolated the kleptochloroplasts from the food vacuole into the dinoflagellate cytoplasm (Kim et al 2012).…”

“…Recently, the process of kleptochloroplast isolation in D. caudata was revealed ultrastructurally (Kim et al 2012). The study showed that D. caudata takes up kleptochloroplasts together with other organelles of M. rubrum into a food vacuole, and then isolated the kleptochloroplasts from the food vacuole into the dinoflagellate cytoplasm (Kim et al 2012). In A. poecilochroum and G. aeruginosum, the chloroplast and cryptomonad organelles were ingested into the dinoflagellate cytoplasm directly, not via a digestive vacuole, making the mechanism of kleptochloroplast incorporation into the dinoflagellate cytoplasm clearly different from that employed by D. caudata.…”

“…The study of the kleptochloroplasts in D. caudata revealed that the structural differences between the chloroplasts within the host and those of the original cryptomonad cell were caused by a rearrangement in the host cell (Kim et al 2012). On the other hand, morphological changes in kleptochloroplasts with time have never been observed in unarmoured kleptochloroplastidic dinoflagellates, especially using the TEM.…”

“…Recently, morphological changes of kleptochloroplasts in Dinophysis caudata were investigated over time from ingestion of prey (Kim et al 2012). The study of the kleptochloroplasts in D. caudata revealed that the structural differences between the chloroplasts within the host and those of the original cryptomonad cell were caused by a rearrangement in the host cell (Kim et al 2012).…”