SxtA and sxtG gene expression and toxin production in the Mediterranean Alexandrium minutum (Dinophyceae).

Federico Perini,Luca Galluzzi,Carmela Dell'Aversano,Luciana Tartaglione,Martino Forino,Fabio Ricci,Patrizia Ciminiello,Antonella Penna,Emma Iacovo

doi:10.3390/md12105258

Federico Perini, Luca Galluzzi + Show 7 more

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https://doi.org/10.3390/md12105258

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Abstract

The dinoflagellate Alexandrium minutum is known for the production of potent neurotoxins affecting the health of human seafood consumers via paralytic shellfish poisoning (PSP). The aim of this study was to investigate the relationship between the toxin content and the expression level of the genes involved in paralytic shellfish toxin (PST) production. The algal cultures were grown both in standard f/2 medium and in phosphorus/nitrogen limitation. In our study, LC-HRMS analyses of PST profile and content in different Mediterranean A. minutum strains confirmed that this species was able to synthesize mainly the saxitoxin analogues Gonyautoxin-1 (GTX1) and Gonyautoxin-4 (GTX4). The average cellular toxin content varied among different strains, and between growth phases, highlighting a decreasing trend from exponential to stationary phase in all culture conditions tested. The absolute quantities of intracellular sxtA1 and sxtG mRNA were not correlated with the amount of intracellular toxins in the analysed A. minutum suggesting that the production of toxins may be regulated by post-transcriptional mechanisms and/or by the concerted actions of alternative genes belonging to the PST biosynthesis gene cluster. Therefore, it is likely that the sxtA1 and sxtG gene expression could not reflect the PST accumulation in the Mediterranean A. minutum populations under the examined standard and nutrient limiting conditions.

Highlights

Dinoflagellates are unicellular protists that play important ecological roles in marine and freshwater habitats
2000 species of dinoflagellates are known to date, most of which are found in marine habitats [1,2]
A. minutum produced exclusively GTX1/4 and the toxin production decreased from exponential to the stationary phase

Summary

Introduction

Dinoflagellates are unicellular protists that play important ecological roles in marine and freshwater habitats. 2000 species of dinoflagellates are known to date, most of which are found in marine habitats [1,2]. Dinoflagellates produce a wide variety of secondary metabolites including a diverse array of toxins that have a significant impact on marine ecosystems and fisheries. Most the classical seafood poisoning syndromes, paralytic- (PSP), diarrhetic- (DSP), neurotoxic- (NSP), azaspiracid shellfish poisoning (AZP), and ciguatera fish poisoning (CFP), are caused by dinoflagellate toxins. In addition to the classic seafood toxins, dinoflagellates may produce a range of other biologically active compounds, including cytotoxins, antibiotics and immunosuppressant compounds [7,8,9]

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