Effects of phosphorus deficiency and adenosine 5'-triphosphate (ATP) on growth and cell cycle of the dinoflagellate Prorocentrum donghaiense

Abstract

Phosphorus (P) is one of the major nutrients required for growth of phytoplankton. While dissolved inorganic phosphorus (DIP) is the preferred form of P, phytoplankton can utilize dissolved organic phosphorus (DOP) when DIP is limited. How DIP deficiency affects the progression of the cell division cycle and how well DOP can restore normal cell cycle in phytoplankton is unclear. Here we investigated the effects of DIP limitation and supply of adenosine 5'-triphosphate (ATP) as sole P-source on the growth and cell cycle in Prorocentrum donghaiense, one of the most common harmful algae bloom dinoflagellates in East China Sea. Part of the culture under DIP-replete condition progressed through a complete cell cycle (G1→S→G2M) in 24h with a typical diel rhythm of each phase, exhibiting a daily growth rate of 0.40d-1 and average cell size 11.19±0.06μm in equivalent spherical diameter. Under phosphorus deficiency, population growth of P. donghaiense averaged at 0.09d-1 and the cell cycle was blocked in G1 phase, while cell size averaged at 11.65±0.05μm. When DIP was replaced by ATP at equivalent molar concentration, the cultures displayed similar growth rate, cell size, and cell cycle oscillation as in the DIP-replete treatment. The results suggest that phosphorus deficiency blocks the cell cycle due to the inability to complete DNA duplication or check-point protein phosphorylation while still allowing photosynthesis and metabolisms, and that DOP such as ATP can fully complement DIP in P. donghaiense.