Nuclear, mitochondrial and plastid gene phylogenies of Dinophysis miles (Dinophyceae): evidence of variable types of chloroplasts.

Abstract

The Dinophysis genus is an ecologically and evolutionarily important group of marine dinoflagellates, yet their molecular phylogenetic positions and ecological characteristics such as trophic modes remain poorly understood. Here, a population of Dinophysis miles var. indica was sampled from South China Sea in March 2010. Nuclear ribosomal RNA gene (rDNA) SSU, ITS1-5.8S-ITS2 and LSU, mitochondrial genes encoding cytochrome B (cob) and cytochrome C oxidase subunit I (cox1), and plastid rDNA SSU were PCR amplified and sequenced. Phylogenetic analyses based on cob, cox1, and the nuclear rRNA regions showed that D. miles was closely related to D. tripos and D. caudata while distinct from D. acuminata. Along with morphology the LSU and ITS1-5.8S-ITS2 molecular data confirmed that this population was D. miles var. indica. Furthermore, the result demonstrated that ITS1-5.8S-ITS2 fragment was the most effective region to distinguish D. miles from other Dinophysis species. Three distinct types of plastid rDNA sequences were detected, belonging to plastids of a cryptophyte, a haptophyte, and a cyanobacterium, respectively. This is the first documentation of three photosynthetic entities associated with a Dinophysis species. While the cyanobacterial sequence likely represented an ectosymbiont of the D. miles cells, the detection of the cryptophyte and haptophyte plastid sequences indicates that the natural assemblage of D. miles likely retain more than one type of plastids from its prey algae for temporary use in photosynthesis. The result, together with recent findings of plastid types in other Dinophysis species, suggests that more systematic research is required to understand the complex nutritional physiology of this genus of dinoflagellates.