Phosphate uptake in Arabidopsis thaliana: dependence of uptake on the expression of transporter genes and internal phosphate concentrations

Changes in the expression of phosphate transporter genes APT1 and APT2, pho sphate uptake and internal phosphate concentrations mere monitored in Arabi dopsis thaliana plants grown with different supplies of inorganic phosphate . When plants were deprived of phosphate, APT1/APT2 expression and phosphat e uptake, measured by both P-32 and phosphate-dependent changes in membrane potential, increased steadily over 4 to 7 d and both were inversely relate d to the internal phosphate concentrations in roots and shoots. When phosph ate was resupplied to phosphate-starved plants, the internal phosphate conc entration and APT1/APT2 expression in roots were restored to control levels within id whereas phosphate uptake took several days to decline to control rates, The increased expression of APT1/ATP2 genes when phosphate supply i s restricted, and its dose relationship with the internal phosphate concent rations in the root, pro,ides evidence that phosphate uptake in Arabidopsis is controlled at least in part, by the synthesis of transporter proteins a s a result of increased transcription of phosphate transporter genes.