The secreted purple acid phosphatase isozymes AtPAP12 and AtPAP26 play a pivotal role in extracellular phosphate-scavenging byArabidopsis thaliana

• Published in: Journal of experimental botany Vol. 63; no. 18; pp. 6531 - 6542
• Main Authors: Robinson, Whitney D., Park, Joonho, Tran, Hue T., Del Vecchio, Hernan A., Ying, Sheng, Zins, Jacqui L., Patel, Ketan, McKnight, Thomas D., Plaxton, William C.
• Format: Journal Article
• Language: English
• Published: Oxford University Press 01.01.2012
• Subjects: Acid soils; Agricultural soils; Agrology; DNA; Liquids; Phosphatases; Phosphates; Plant roots; Plants; RESEARCH PAPER; Seedlings
• ISSN: 0022-0957; 1460-2431

Orthophosphate (Pi) is an essential but limiting macronutrient for plant growth. Extensive soil P reserves exist in the form of organic P (Pₒ), which is unavailable for root uptake until hydrolysed by secretory acid phosphatases (APases). The predominant purple APase (PAP) isozymes secreted by roots of Pi-deficient (−Pi)Arabidopsis thalianawere recently identified as AtPAP12 (At2g27190) and AtPAP26 (At5g34850). The present study demonstrated that exogenous Pₒ compounds such as glycerol-3-phosphate or herring sperm DNA: (i) effectively substituted for Piin supporting the P nutrition ofArabidopsisseedlings, and (ii) caused upregulation and secretion of AtPAP12 and AtPAP26 into the growth medium. When cultivated under −Piconditions or supplied with Pₒ as its sole source of P nutrition, anatpap26/atpap12T-DNA double insertion mutant exhibited impaired growth coupled with >60 and >30% decreases in root secretory APase activity and rosette total Piconcentration, respectively. Development of theatpap12/atpap26mutant was unaffected during growth on Pi-replete medium but was completely arrested when 7-day-old Pi-sufficient seedlings were transplanted into a −Pi, Pₒ-containing soil mix. Both PAPs were also strongly upregulated on root surfaces and in shoot cell-wall extracts of −Piseedlings. It is hypothesized that secreted AtPAP12 and AtPAP26 facilitate the acclimation ofArabidopsisto nutritional Pi deficiency by: (i) functioning in the rhizosphere to scavenge Pifrom the soil’s accessible Pₒ pool, while (ii) recycling Pifrom endogenous phosphomonoesters that have been leaked into cell walls from the cytoplasm. Thus, AtPAP12 and AtPAP26 are promising targets for improving crop P-use efficiency.