Unveiling the impact of glycerol phosphate (DOP) in the dinoflagellate Peridinium bipes by physiological and transcriptomic analysis

The ability to use dissolved organic phosphorus (DOP) is important for survival and competition when phytoplankton are faced with scarcity of dissolved inorganic phosphorus (DIP). However, phosphorus availability to the freshwater dinoflagellate Peridinium bipes has received relatively little attention, the efficiency of glycerol phosphate use by phytoplankton has rarely been investigated, and the regulatory molecular mechanisms remain unclear. In the present study, cultures of the freshwater dinoflagellate Peridinium bipes were set up in 119 medium (+DIP), DIP-depleted 119 medium (P-free), and β-glycerol phosphate-replacing-DIP medium (+DOP). Gene expression was analyzed using transcriptomic sequencing. The growth rate of cells in DOP treatment group was similar to that in DIP group, but chlorophyll a fluorescence parameters RC/CS0, ABS/CS0, TR0/CS0, ET0/CS0 and RE0/CS0 markedly decreased in the DOP group. Transcriptomic analysis revealed that genes involved in photosynthesis, including psbA, psbB, psbC, psbD, psaA and psaB, were downregulated in the DOP group relative to the DIP group. Glycerol-3-phosphate dehydrogenase and glyceraldehyde-3-phosphate dehydrogenase, rather than alkaline phosphatase, were responsible for β-glycerol phosphate use. Intercellular gluconeogenesis metabolism was markedly changed in the DOP group. In addition, genes involved in ATP synthases, the TCA cycle, oxidative phosphorylation, fatty acid metabolism and amino acid metabolism in P. bipes were significantly upregulated in the DOP group compared with the DIP treatment. These findings suggested that β-glycerol phosphate could influence the photosynthesis and metabolism of P. bipes, which provided a comprehensive understanding of the phosphorus physiology of P. bipes. The mechanisms underlying the use of β-glycerol phosphate and other DOPs are different in different species of dinoflagellates and other phytoplankton. DIP reduction may be more effective in controlling the bloom of P. bipes than DOP reduction.