Role of acid phosphatase in the tolerance of the rhizobial symbiosis with legumes to phosphorus deficiency

International audiencePhosphorus (P) deficiency initiates a myriad of transcriptional, biochemical and physiological responses stimulating either the root’s extracellular abilities to acquire soil P in the rhizosphere or optimize its intracellular use efficiency and allocation through all plant organs. Enhancing activity of acid phosphatase (APase) to acquire and remobilize Pi from organic P compounds is one important strategy for improving plant P nutrition. The release of APase to the rhizosphere is a typical and almost universal P-starvation response in higher plants. However, relatively little is known about the functions of intracellular APase in legume nodules. The aim of this review was to track the enzyme activity along with the intra-nodular localization of APase, and its contribution in the rhizobial symbiosis tolerance to P-deficiency. Our findings have revealed that expression of APase and phytases genes and activities of the corresponding enzymes were positively correlated with increases both of the P use efficiency for N2 fixation and nodule O2 permeability in the rhizobial symbiosis with legumes. The induced enzyme activity and the marked transcripts localization of APase and phytase in nodule cortex would control nodule respiration and contribute to adaptation of nodulated legumes to low-P availability. Thus, the increase of APase and phytase activities in legume nodules supports a physiological role of these enzymes in the regulation of nitrogenase activity in connection with the nodule-P status, and opens up a new scenario for a better understanding of the regulation of N2 fixation in legumes