Mono- and digalactosyldiacylglycerol composition of dinoflagellates. V. The galactolipid profile of Alexandrium tamarense (Dinophyceae) during the course of infection by the parasitic syndinian dinoflagellate Amoebophrya sp.

Amoebophrya is a parasitic, syndinian dinoflagellate genus that must infect another host dinoflagellate in order to reproduce. Work by Park et al. [Mar. Ecol. Prog. Ser., 227: 281–292 (2002)] has led to the hypothesis that Amoebophrya's development within a host cell nucleus disrupts the flow of genetic information involved in plastidial function. The possibility that genetic disruption by this parasite could lead to alterations in plastidial lipid composition during the course of an infection has not yet been elucidated. Our primary objective in this lipidomic study was to examine the chloroplast membrane galactolipid composition of Alexandrium tamarense infected by an Amoebophrya species in order to determine whether infection of A. tamarense causes a phenotypic alteration in the composition of mono- and digalactosyldiacylglycerol (MGDG and DGDG, respectively), two galactolipids that comprise the majority of photosynthetic membranes. Our secondary objective was to determine if non-photosynthetic Amoebophrya sp. either incorporated host cell MGDG and DGDG, and/or itself produced forms of MGDG and DGDG, as has been observed previously in heterotrophic apicomplexan parasites distantly related to Amoebophrya. We found that, despite development of Amoebophrya sp. within the nucleus, the composition of A. tamarense MGDG and DGDG did not change throughout the infection process. The predominant forms of these galactolipids were 18:5/18:4 (sn???1/sn?2) and 20:5/18:4 DGDG, which were present at similar abundances in both an uninfected host and a host late in the infection process just prior to release of Amoebophrya sp. dinospores. Amoebophrya sp. did not possess appreciable amounts of any forms of MGDG and DGDG.