Fig. 1
PII expression is increased by nitrate. a Time course of the GLB1 transcripts accumulation during incubation of illuminated cells in nitrate-containing medium. Chlamydomonas cells of cw15–325 strain were grown in ammonium-containing medium (Con, control) and transferred to media containing 4 mM, 100 μM, or 10 μM NO3− in the light for 0.5 h, 1 h, 2 h or 4 h. Values are means ± SE of three biological replicates and three technical replicates and are given as expression level relative to a house-keeping gene RACK1 that has a value of 1.The increase in NIT1 transcript abundance was used as a positive control (insertion). b Changes in nitrate levels in the media. Chlamydomonas cells of cw15–325 strain were grown in ammonium-containing medium and transferred to media containing 4 mM, 100 μM, or 10 μM NO3− in the light. At the indicated times, the amounts of nitrate present in the media were quantified. ND, not determined. Values are means ± SE of three biological replicates. cTime course of the PII protein accumulation during incubation of illuminated cells in nitrate-containing medium. PII levels were analyzed by western blotting in the same conditions as in (a). Each line corresponds to 20 μg of soluble proteins extracted from samples taken from cultures at the time points indicated. Quantitation of protein blots is given as proportion of signal in test variant to control variant. HSP70B signal served as a loading control