Freezing tolerance of sea urchin embryo pigment cells

Various stresses, including exposure to cold or heat, can result in a sharp increase in pigmentation of sea urchin embryos and larvae. The differentiation of pigment cells is accompanied by active expression of genes involved in the biosynthesis of naphthoquinone pigments and appears to be a part of the defense system protecting sea urchins against harmful factors. To clarify numerous issues occurring at various time points after the cold injury, we studied the effect of shikimic acid, a precursor of naphthoquinone pigments, on cell viability and expression of some pigment genes such as the pks and sult before and after freezing the cultures of sea urchin embryo cells. The maximum level of the pks gene expression after a freezing–thawing cycle was found when sea urchin cells were frozen in the presence of trehalose alone. Despite naphthoquinone pigments have been reported to possess antioxidant and cryoprotectant properties, our data suggest that shikimic acid does not have any additional cryoprotective effect on freezing tolerance of sea urchin embryo pigment cells.