Nutrient uptake and transporter gene expression of ammonium, nitrate, and phosphorus in Ulva linza: adaption to variable concentrations and temperatures

Abstract

An increase in the human population has caused eutrophication in shore water due to the release of nitrogen and phosphorus. Green tides caused by the proliferation of green macroalgae are an important direct consequence of eutrophication worldwide. We studied the nutrient uptake rate (NUR) and the expression of nutrient transporter genes in the green alga Ulva linza, an alga which forms green tides almost every summer in the Yellow Sea, and identified 6 nutrient transporter genes which contributed to the uptake of ammonium, nitrate, and phosphorus. Two environmental conditions, temperature and nutrient concentration, were found to significantly influence the NUR and gene expression of nutrient transporters. The optimum concentrations for uptake of ammonium, nitrate, and phosphorus were 1398.7, 710.4, and 230.7 μmol L−1 respectively, while the optimum temperature was 15 °C. Six nutrient transporter genes (amt1, amt2, and amt3 for ammonium uptake, nit for nitrate uptake, hapt, and lapt for phosphorus) were found to have an optimal working environment in terms of temperature and nutrient concentration, respectively.