A Phosphate-Starvation Enhanced Purple Acid Phosphatase, GmPAP23 Mediates Intracellular Phosphorus Recycling and Yield in Soybean.

Plant internal phosphorus (P) recycling is a complex process, which is vital for improving plant P use efficiency. However, the mechanisms underlying phosphate (Pi) release from internal organic-P form remains to be deciphered in crops. Here, we functionally characterised a Pi-starvation responsive purple acid phosphatase (PAP), GmPAP23 in soybean (Glycine max). GmPAP23 could hydrolyse a series of Pi-containing compounds in vitro, such as trehalose-6-phosphate and glucose-l-phosphate. Moreover, GmPAP23 overexpression led to less P distribution in soybean source organs, including mature leaves and pod shells, but more P distribution in seeds under P sufficient conditions, although no effect was observed for transgenic soybean lines with its suppression. Metabolomic analysis found that a group of P-containing metabolites exhibited differential accumulations in mature leaves between wild type (WT) and GmPAP23 overexpression lines, such as glucose-l-phosphate and trehalose-6-phosphate. Moreover, a MYB transcription factor, GmPHR14 was subsequently found to activate the transcription of GmPAP23 via directly binding to its promoter. Collectively, these findings could highlight that the GmPHR14-GmPAP23 pathway, which controls internal P recycling in soybean, and thus affect yield.