The cell wall‐targeted purple acid phosphatase AtPAP25 is critical for acclimation of Arabidopsis thaliana to nutritional phosphorus deprivation. (November 2014)

• Record Type: Journal Article
• Authors: Del Vecchio, Hernan A.; Ying, Sheng; Park, Joonho; Knowles, Vicki L.; Kanno, Satomi; Tanoi, Keitaro; She, Yi‐Min; Plaxton, William C.
• Is Part Of: Plant journal. Volume 80:Number 4(2014:Nov.)
• Page Start: 569
• Page End: 581
• Publication Date: 2014-11
• Subjects: Plant molecular biology -- Periodicals; Plant cells and tissues -- Periodicals; Botany -- Periodicals; 580
• DOI: 10.1111/tpj.12663
• Languages: English
• ISSNs: 0960-7412

Abstract

<abstract abstract-type="main" id="tpj12663-abs-0001"> <title>Summary</title> <p>Plant purple acid phosphatases (PAPs) belong to a relatively large gene family whose individual functions are poorly understood. Three PAP isozymes that are up‐regulated in the cell walls of phosphate (Pi)‐starved (−Pi) <italic>Arabidopsis thaliana</italic> suspension cells were purified and identified by MS as AtPAP12 (At2g27190), AtPAP25 (At4g36350) and AtPAP26 (At5g34850). AtPAP12 and AtPAP26 were previously isolated from the culture medium of −Pi cell cultures, and shown to be secreted by roots of Arabidopsis seedlings to facilitate Pi scavenging from soil‐localized organophosphates. AtPAP25 exists as a 55 kDa monomer containing complex NX(S/T) glycosylation motifs at Asn172, Asn367 and Asn424. Transcript profiling and immunoblotting with anti‐AtPAP25 immune serum indicated that AtPAP25 is exclusively synthesized under −Pi conditions. Coupled with potent mixed‐type inhibition of AtPAP25 by Pi (<italic>I</italic><sub>50</sub> = 50 μ<sc>m</sc>), this indicates a tight feedback control by Pi that prevents AtPAP25 from being synthesized or functioning as a phosphatase except when Pi levels are quite low. Promoter–GUS reporter assays revealed <italic>AtPAP25</italic> expression in shoot vascular tissue of −Pi plants. Development of an <italic>atpap25</italic> T‐DNA insertion mutant was arrested during cultivation on soil lacking soluble Pi, but rescued upon Pi fertilization or complementation with <italic>AtPAP25</italic>. Transcript profiling by quantitative RT‐PCR indicated that Pi starvation signaling was attenuated in the <italic>atpap25</italic> mutant. AtPAP25 exhibited near‐optimal phosphatase activity with several phosphoproteins and phosphoamino acids as substrates. We hypothesize that AtPAP25 plays a key signaling role during Pi deprivation by functioning as a phosphoprotein phosphatase rather than as a non‐specific scavenger of Pi from extracellular P‐monoesters.</p> </abstract>