Abstract
To investigate the mechanism for the production of paralytic shellfish toxins (PST) in toxic dinoflagellates, with a 2D-gel based approach, we had made two sets of proteomic comparisons: (a) between a toxic Alexandrium catenella (AC-T) and a phylogenetically closely related non-toxic strain (AC-N), (b) between toxic AC-T grown in a medium with 10% normal amount of phosphate (AC-T-10%P) known to induce higher toxicity and AC-T grown in normal medium. We found that photosynthesis and energy production related proteins were up-regulated in AC-T when compared to AC-N. However, the same group of proteins was down-regulated in AC-T-10%P when compared to normal AC-T. Examining the relationship of photosynthesis and toxin content of AC-T upon continuous photoperiod experiment revealed that while growth and associated toxin content increased after 8 days of continuous light, toxin content maintained constant when cells were shifted from continuous light to continuous dark for 3 days. This emphasized the cruciality of light availability on toxin biosynthesis in AC-T, while another light-independent mechanism may be responsible for higher toxicity in AC-T-10%P compared to normal AC-T. Taken all together, it is believed that the interplay between “illumination”, “photosynthesis”, “phosphate availability”, and “toxin production” is much more complicated than what we had previously anticipated.
Highlights
Paralytic shellfish poisoning (PSP) is the intoxication with paralytic shellfish toxins (PST) caused by the consumption of contaminated shellfish
The occurrence of harmful algal blooms (HABs) induced by PST-producing microalgae could bring forth enormous negative economic impact as it may cause prolonged closure of molluscan shellfish harvesting areas and fishing grounds
The apparent opposite sets of results are interesting, but its interpretation is difficult. To follow this up, we investigated if light and photosynthesis are the drivers for PST production and because Alexandrium catenella (AC-T)-10%P cells did not survive well with prolonged cultivation, A. catenella (AC)-T
Summary
Paralytic shellfish poisoning (PSP) is the intoxication with paralytic shellfish toxins (PST) caused by the consumption of contaminated shellfish. The occurrence of harmful algal blooms (HABs) induced by PST-producing microalgae could bring forth enormous negative economic impact as it may cause prolonged closure of molluscan shellfish harvesting areas and fishing grounds. Alexandrium, Gymnodinium, and Pyrodinium are the three genera of marine dinoflagellates that are known to produce PST [3]. Phycological studies had found that there are variations of toxin content and profile among different species as well as strains of the dinoflagellates [4,5,6]. Other studies reported that the extent of PST production of these organisms could be influenced by certain physical or nutritional factors, such as the increase in toxicity of Alexandrium sp. Van de Waal et al [13]
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