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, phosphate uptake and internal phosphate concentrations were monitored in Arabidopsis thaliana plants grown with different supplies of inorganic phosphate. When plants were deprived of phosphate, APT1/APT2 expression and phosphate uptake, measured by both 32P and phosphate-dependent changes in membrane potential, increased steadily over 4 to 7 d and both were inversely related to the internal phosphate concentrations in roots and shoots. When phosphate was resupplied to phosphate-starved plants, the internal phosphate concentration and APT1/APT2 expression in roots were restored to control levels within 1 d whereas phosphate uptake took several days to decline to control rates. The increased expression of APT1/ATP2 genes when phosphate supply is restricted, and its close relationship with the internal phosphate concentrations in the root, provides evidence that phosphate uptake in Arabidopsis is controlled, at least in part, by the synthesis of transporter proteins as a result of increased transcription of phosphate transporter genes.