De novo transcriptome of the newly described phototrophic dinoflagellate Yihiella yeosuensis: comparison between vegetative cells and cysts

Abstract

Dinoflagellates are often responsible for red tides or harmful algal blooms. Many dinoflagellates move quickly to capture prey cells, escape from predation, and conduct diurnal vertical migrations, but they form cysts (non-motile stage) when growth conditions are not favorable. To investigate differences in gene expression between vegetative cells and cysts of dinoflagellates, transcriptomes of the newly described dinoflagellate Yihiella yeosuensis, one of the fastest dinoflagellates, at the cysts and vegetative cells were de novo assembled. The gene expression profiles of Y. yeosuensis showed 5479 up-regulated and 4790 down-regulated significantly differentially expressed genes, when cells changed from the vegetative cells to cysts. In particular, polyketide synthase' and cell-wall biogenesis' genes, related to anti-predation, were highly up-regulated, whereas flagellum-related genes, related to motility, were generally down-regulated. Among the flagellum-related genes of Y. yeosuensis, the central pair' and radial spoke' genes, related to direct flagellar movement, were most down-regulated genes. When approximately a hundred flagellum-related genes of motile and non-motile microalgae and plants were analyzed, the number of the genes increased with increasing motility, and furthermore, there was a considerable difference in the presence of the central pair' and radial spoke' genes among the motile microalgae. Therefore, high down-regulation of the central pair' and radial spoke' genes when Y. yeosuensis cells change from the motile to non-motile stage is possibly related to the presence of these genes in microalgae and plants in their evolution. Conclusively, when Y. yeosuensis form cysts, motility might trade off with anti-predation.