The Role of Intracellular and Secreted Purple Acid Phosphatases in Plant Phosphorus Scavenging and Recycling

Purple acid phosphatases (PAPs) belong to a special group of acid phosphatases (APases), which hydrolyse phosphate from phosphomonoesters and anhydrides with an optimum pH below 7.0. Although some PAPs have been shown to play a vital role in plant adaptation to phosphorus (P) deficiency, precise functions of most PAPs remain fragmentary due to their diversity and ubiquity. A combined application of genetic, biochemical and physiological approaches is required to integrate all available knowledge of PAP properties into a mosaic of functional roles. The chapter aim is to summarize and integrate the structural, biochemical (e.g. substrate specificity) and molecular (e.g. subcellular localisation, transcriptional and post-transcriptional regulation) characteristics of PAPs, which might facilitate further understanding of their complex functions, especially in relation to P scavenging and recycling in plants. Increased insights into the physiological roles of PAPs will be essential to improve crop P acquisition and utilisation efficiency through the tools of biotechnology, so as to reduce or eliminate humankind's overuse of nonrenewable P-containing fertilizers.