Plastid-Associated Genes in Dinoflagellates Identified by cDNA Screening and Expression Analysis

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Abstract The project will explore the genetic and genomic properties of dinoflagellates, with the aim of using genomic techniques to study the integration of the peridinin-type plastid into its host cell. The specific goals of the project are 1) to identify the most suitable dinoflagellate species for molecular genetic studies 2) to examine the fundamental properties of the nuclear, chloroplast, and mitochondrial genomes in this dinoflagellate, and explore its suitability for genomic studies, and 3) to generate a cDNA library that has been enriched for rare transcripts, sequence several hundred clones from this library, and screen these sequences for plastid-associated genes. One key question is why these organisms have such remarkably large genomes; it is not clear that the complexity of the genomes matches its large size. To understand the organization of the dinoflagellate genome, it will also be important to determine whether the genome is polyploid, and the extent to which dinoflagellate genes are encoded as polygenes. This, in concert with the identification of plastid-associated genes, will lead to an understanding of dinoflagellate genome organization, and the genetic integration of the plastid into the host cell. Dinoflagellates are a distinctive group of flagellate protists that are distantly related to most model organisms, and have many features that are unusual among eukaryotes. They are important members of both marine and freshwater plankton communities, and can be responsible for harmful algal blooms and toxin production. While there are several types of plastids (chloroplasts) found in dinoflagellates, the majority of photosynthetic dinoflagellates rely on plastids that include the pigment peridinin, along with chlorophylls a and c. These peridinin-type plastids are bound by three membranes. The project will explore the genetic and genomic properties of dinoflagellates, with the aim of using genomic techniques to study the integration of the peridinin-type plastid into its host cell. Relatively little genetic work has been performed with dinoflagellates, so the project will emphasize investigations into fundamental genetic properties such as the size and gene content of the nuclear genome, the degree to which poly-A tails are present on gene transcripts, and the basis for interaction between the nucleus and plastid.