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Comparative gene expression in toxic versus non-toxic strains of the marine dinoflagellate Alexandrium minutum.

Yang I, John U, Beszteri S, Glöckner G, Krock B, Goesmann A, Cembella AD - BMC Genomics (2010)

Bottom Line: 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Alfred-Wegener-Institut für Polar-und Meeresforschung, Bremerhaven, Germany.

ABSTRACT

Background: 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.

Results: 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.

Conclusions: 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.

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Increase of cell number and culture toxin content in strain AL3T over 24 hours. Grey boxes = dark phase, circles = cell numbers, diamonds = total PSP toxins mL-1.
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Figure 2: Increase of cell number and culture toxin content in strain AL3T over 24 hours. Grey boxes = dark phase, circles = cell numbers, diamonds = total PSP toxins mL-1.

Mentions: Under our standard growth conditions, the toxin-producing strain AL3T exhibited a growth rate (1.01 cell divisions day-1; I. Yang, unpublished data) that approximated the total length of the light:dark period, which suggested that these cultures might have a naturally circadian-phased cell cycle. In the triplicate cultures examined, however, both cell number and culture toxin content increased over the entire light phase. The toxin content per cell stayed roughly the same during the whole day, while cell numbers doubled from 3,271 ± 296 to 7,167 ± 482 cells mL-1 within 24 h. The toxin content of the culture increased from 1.38 ± 0.16 ng μL-1 to 3.24 ± 0.21 ng μL-1 (Fig. 2)


Comparative gene expression in toxic versus non-toxic strains of the marine dinoflagellate Alexandrium minutum.

Yang I, John U, Beszteri S, Glöckner G, Krock B, Goesmann A, Cembella AD - BMC Genomics (2010)

Increase of cell number and culture toxin content in strain AL3T over 24 hours. Grey boxes = dark phase, circles = cell numbers, diamonds = total PSP toxins mL-1.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2874808&req=5

Figure 2: Increase of cell number and culture toxin content in strain AL3T over 24 hours. Grey boxes = dark phase, circles = cell numbers, diamonds = total PSP toxins mL-1.
Mentions: Under our standard growth conditions, the toxin-producing strain AL3T exhibited a growth rate (1.01 cell divisions day-1; I. Yang, unpublished data) that approximated the total length of the light:dark period, which suggested that these cultures might have a naturally circadian-phased cell cycle. In the triplicate cultures examined, however, both cell number and culture toxin content increased over the entire light phase. The toxin content per cell stayed roughly the same during the whole day, while cell numbers doubled from 3,271 ± 296 to 7,167 ± 482 cells mL-1 within 24 h. The toxin content of the culture increased from 1.38 ± 0.16 ng μL-1 to 3.24 ± 0.21 ng μL-1 (Fig. 2)

Bottom Line: 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Alfred-Wegener-Institut für Polar-und Meeresforschung, Bremerhaven, Germany.

ABSTRACT

Background: 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.

Results: 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.

Conclusions: 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.

Show MeSH
Related in: MedlinePlus