The marine dinoflagellate Karenia brevis produces a suite of poly-ether ladder neurotoxins known as brevetoxins (PbTx). Large scale blooms of K. brevis occur around the coast of Florida and the Gulf of Mexico nearly every year. Millions of dollars in damages to coastal economies have been linked to harmful algal blooms (HABs). The endogenous function of brevetoxin remains unknown. Hypotheses have included a role as a feeding deterrent or mediator of osmotic regulation. However, not all strains of K. brevis are the same; some strains can produce up to 60 pg/cell of PbTx, while others produce less than 1 pg/cell. Comparison of high and low-toxic strains may provide clues to the role brevetoxins play for K. brevis. The high and low-toxic strains differ considerably, not only in their production of brevetoxin, but in their ability to perform non-photochemical quenching (NPQ) or the dissipation of excess light energy as heat. Whether the lack of the toxin causes the NPQ deficiency, or whether the NPQ deficiency results in lower toxin production is yet undetermined. The xanthophyll cycle is central to energy dependent non-photochemical quenching (qE). In dinoflagellates, diadinoxanthin is converted to diatoxanthin by enzymatic de-epoxidation of diadinoxanthin via diadinoxanthin de-epoxidase (DDE). We have shown that the low toxic strain of K. brevis is deficient in performing this de-epoxidation. However, the source of this deficiency is not understood. It may be a result of differences in expression of DDE or differences in activity due to the redox status of the cell. The q-RT-PCR studies done in our lab present the differences in relative amounts of DDE activity in high and low toxic strains of K. brevis over a growth cycle.

Differences in xanthophyll de-epoxidase activity in high and low toxic strains of K. brevis

2019 Spring National Meeting

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