Grazer-induced toxin formation in dinoflagellates: a transcriptomic model study

Abstract

The cosmopolitan marine dinoflagellate Alexandrium minutum is known to produce toxins causing paralytic shellfish poisoning (PSP). As has recently been shown, this toxicity can be enhanced by the presence of certain copepod species. Inducible defences are known from a variety of marine organisms, but the associated transcriptomic changes have only been investigated in model angiosperms. Here, we use a microarray approach to investigate the changes in gene expression during the copepodprovoked induction of higher toxicity in A. minutum. We found a limited set of 14 genes (0.35% of the tested sequences) to be affected by copepod presence; gene expression changed by a factor of 1.9 to 11.4 when compared with control samples. We compared the differentially expressed genes after one day -before the onset of augmented toxicity -and after 3 days, when cellular toxin content in the induced samples was five times higher than in control cultures. Comparison with differences previously found between toxic and non-toxic strains revealed two sequences apparently associated with PSP toxin content. Our study is the first investigation of transcriptomic effects associated with grazer-induced induction of elevated toxicity in a protist. This provides a novel approach to the ecology of predator-prey interactions, as well as a highly targeted method for investigating the genes associated with toxin production and regulation in toxic dinoflagellates.

Current Knowledge and Recent Advances in Marine Dinoflagellate Transcriptomic Research

“…Although this study found that grazers induced toxin production in dinoflagellates and this is supported by several studies on grazing effect to the toxin production in dinoflagellates, two upregulated genes that could be annotated in this study are unlikely to be directly involved in PSP toxin synthesis [48,[58][59][60].…”

Fight and flight in dinoflagellates? Kinetics of simultaneous grazer‐induced responses in Alexandrium tamarense

“…A treatment where algae have been acclimatized to grazers for at least two cell divisions can be included to achieve this. The presence of more than one grazer-induced response suggests that unbiased screening methods like transcriptomics, proteomics, and metabolomics may be useful complements to traditional methods in order to comprehend the full response of phytoplankton to grazer cues (Yang et al 2011). …”

Growth- and nutrient-dependent gene expression in the toxigenic marine dinoflagellate Alexandrium minutum

“…Two recent studies investigated changes in the transcriptome of A. tamarense and A. minutum in cultures with elevated cell toxin quotas after exposure to such grazers (Wohlrab et al, 2010;Yang et al, 2011). The same microarray probes were used in these investigations as in the present study, either alone or as part of a larger set.…”