Comparative gene expression in toxic versus non-toxic strains of the marine dinoflagellate Alexandrium minutum
1 Alfred-Wegener-Institut für Polar-und Meeresforschung, Am Handelshafen 12, 27570 Bremerhaven, Germany
2 School of Biosciences, University of Exeter, Stocker Road, Exeter, EX4 4QD, UK
3 Fritz Lipmann Institute for Age Research, Beutenbergstraß 11, 07745 Jena, Germany
4 Institute for Biochemistry I, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Cologne, Germany
5 Berlin Center for Genomics in Biodiversity Research, Königin-Luise-Str. 1-3, 14195 Berlin, Germany
6 Universität Bielefeld, CeBiTec, 33594 Bielefeld, Germany
BMC Genomics 2010, 11:248 doi:10.1186/1471-2164-11-248Published: 19 April 2010
The dinoflagellate Alexandrium minutum typically produces paralytic shellfish poisoning (PSP) toxins, which are known only from cyanobacteria and dinoflagellates. While a PSP toxin gene cluster has recently been characterized in cyanobacteria, the genetic background of PSP toxin production in dinoflagellates remains elusive.
We constructed and analysed an expressed sequence tag (EST) library of A. minutum, which contained 15,703 read sequences yielding a total of 4,320 unique expressed clusters. Of these clusters, 72% combined the forward-and reverse reads of at least one bacterial clone. This sequence resource was then used to construct an oligonucleotide microarray. We analysed the expression of all clusters in three different strains. While the cyanobacterial PSP toxin genes were not found among the A. minutum sequences, 192 genes were differentially expressed between toxic and non-toxic strains.
Based on this study and on the lack of identified PSP synthesis genes in the two existent Alexandrium tamarense EST libraries, we propose that the PSP toxin genes in dinoflagellates might be more different from their cyanobacterial counterparts than would be expected in the case of a recent gene transfer. As a starting point to identify possible PSP toxin-associated genes in dinoflagellates without relying on a priori sequence information, the sequences only present in mRNA pools of the toxic strain can be seen as putative candidates involved in toxin synthesis and regulation, or acclimation to intracellular PSP toxins.