title: Paralytic shellfish toxin content is related to genomic sxtA4 copy number in Alexandrium minutum strains.
abstract: Dinoflagellates are microscopic aquatic eukaryotes with huge genomes and an unusual cell regulation. For example, most genes are present in numerous copies and all copies seem to be obligatorily transcribed. The consequence of the gene copy number (CPN) for final protein synthesis is, however, not clear. One such gene is sxtA, the starting gene of paralytic shellfish toxin (PST) synthesis. PSTs are small neurotoxic compounds that can accumulate in the food chain and cause serious poisoning incidences when ingested. They are produced by dinoflagellates of the genera Alexandrium, Gymnodium, and Pyrodinium. Here we investigated if the genomic CPN of sxtA4 is related to PST content in Alexandrium minutum cells. SxtA4 is the 4th domain of the sxtA gene and its presence is essential for PST synthesis in dinoflagellates. We used PST and genome size measurements as well as quantitative PCR to analyze sxtA4 CPN and toxin content in 15 A. minutum strains. Our results show a strong positive correlation between the sxtA4 CPN and the total amount of PST produced in actively growing A. minutum cells. This correlation was independent of the toxin profile produced, as long as the strain contained the genomic domains sxtA1 and sxtA4.
authors.affiliation: Department of Biosciences, University of Oslo Oslo, Norway.
authors.forename: Anke
authors.initials: A
authors.lastname: Stüken
authors.affiliation: U.A. Microalgas Nocivas (Consejo Superior de Investigaciones Científicas - Instituto Español de Oceanografía), Instituto de Investigaciones Marinas Vigo, Spain.
authors.forename: Pilar
authors.initials: P
authors.lastname: Riobó
authors.affiliation: U.A. Microalgas Nocivas (Consejo Superior de Investigaciones Científicas - Instituto Español de Oceanografía), Instituto de Investigaciones Marinas Vigo, Spain.
authors.forename: José
authors.initials: J
authors.lastname: Franco
authors.affiliation: Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo Oslo, Norway.
authors.forename: Kjetill S
authors.initials: KS
authors.lastname: Jakobsen
authors.affiliation: Laboratoire Adaptation et Diversité en Milieu Marin, CNRS, UMR 7144 Roscoff, France ; Sorbonne Universités - Université Pierre et Marie Curie, UMR 7144 Roscoff, France.
authors.forename: Laure
authors.initials: L
authors.lastname: Guillou
authors.affiliation: Aquatic Ecology, Lund University Lund, Sweden ; U.A. Microalgas Nocivas (Consejo Superior de Investigaciones Científicas - Instituto Español de Oceanografía), Instituto Español de Oceanografía Vigo, Spain.
authors.forename: Rosa I
authors.initials: RI
authors.lastname: Figueroa
keywords: Alexandrium; Dinoflagellate; copy number variation; gene dosage; genome size; paralytic shellfish toxin (PST); saxitoxin (STX); sxtA