(A) Electron microscopy transmission image of A. ceratii dinospore showing the fine structure of the mitochondrion (Mi), nucleus (Nc), and flagella (Fl). Confocal microscopy images showing (B) SYTO-13–stained DNA of the nucleus (Nc), (C) mitochondria stained with MitoTracker, (D) an image of a free-swimming biflagellate dinospore cell, and (E) overlay of images. Photo from John et al. 2019. [CC BY-NC 4.0]

The Amoebophrya ceratii AT5.2 genome sequence and gene models have not been determined by the JGI, but were downloaded from John et al. 2019 on September 16, 2019. In order to ensure this genome is comparable to those sequenced by the JGI, we applied filters to remove if present: 1) transposable elements, 2) pseudogenes, 3) alternative transcripts and overlapping models, 4) alleles on secondary scaffolds and 5) unsupported short models. This resulted in the removal of 1767 models and the generation of the FilteredModels1 (GeneCatalog) gene track. All published models are available in the ExternalModels track. Please note that this copy of the genome is not maintained by NCBI and is therefore not automatically updated. In order to allow comparative analyses with other algal genomes sequenced by the JGI, a copy of this genome is incorporated into PhycoCosm. The JGI Annotation Pipeline was used to add functional annotation to the genes.

The following text is modified from John et al. 2019:

Dinoflagellates are microbial eukaryotes that have exceptionally large nuclear genomes; however, their organelle genomes are small and fragmented and contain fewer genes than those of other eukaryotes. The genus Amoebophrya (Syndiniales) comprises endoparasites with high genetic diversity that can infect other dinoflagellates, such as those forming harmful algal blooms (e.g., Alexandrium). We sequenced the genome (~100 Mb) of Amoebophrya ceratii to investigate the early evolution of genomic characters in dinoflagellates. The A. ceratii genome encodes almost all essential biosynthetic pathways for self-sustaining cellular metabolism, suggesting a limited dependency on its host. Although dinoflagellates are thought to have descended from a photosynthetic ancestor, A. ceratii appears to have completely lost its plastid and nearly all genes of plastid origin. Functional mitochondria persist in all life stages of A. ceratii, but we found no evidence for the presence of a mitochondrial genome. Instead, all mitochondrial proteins appear to be lost or encoded in the A. ceratii nucleus.