Influences of external nutrient conditions on the transcript levels of a nitrate transporter gene in Skeletonema costatum

To verify the feasibility of high-affinity nitrate transporter gene (Nrt2) as an indicator of nitrogen status, changes in the transcript levels of transcripts associated with phosphate starvation and different nitrate concentrations were studied using real-time quantitative reverse-transcription PCR (QRT-PCR) technology in batch cultures of Skeletonema costatum. The results show that compared with P-replete condition, P starvation could reduce the Nrt2 transcript levels apparently. Nrt2 transcript levels had a significant negative linear correlation with nitrate concentrations below 40 μmol/L. The results of 48 h short-term incubation experiment under different nitrate concentrations confirmed this correlation, and the following regression equation is built:y=-3.305x+98.95, R²=0.988, where x represents nitrate concentrations (<40 μmol/L) and y represents the Nrt2 transcript levels.