Phosphatase secretion mutants in Arabidopsis thaliana

Phosphatases are important enzymes for understanding plant phosphorus relations. Plant-derived soil phosphatases may help plants during phosphorus deficiency by mobilizing organic phosphorus for plant uptake. In microbes, phosphatases and other responses to phosphorus deficiency are controlled at the transcriptional level by the PHO regulon, and evidence is mounting for the existence of a plant PHO regulon. By isolating Arabidopsis mutants for phosphatase secretion, components of a plant PHO regulon may be identified. Identification and characterization of constitutive phosphatase secretion (cps) mutants showed that root-bound phosphatase activity can be increased, and that under low-phosphorus conditions this increased activity can preserve higher root phosphate concentrations, however, there may be a physiological cost in growth associated with this trait. Characterization of the phosphatase under-producing (pup) mutants revealed that acid phosphatases can alter whole-plant phosphorus relations, that secreted phosphatases are important for acquiring and/or maintaining phosphate levels when grown in a soil substrate with an organic P component, and that secreted phosphatases are probably under post-transcriptional control. Although the cps and pup mutants are not defective in P deficiency responses, these mutants give us insight into physiologically important components of plant P regulation.