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The cell wall‐targeted purple acid phosphatase At PAP 25 is critical for acclimation of Arabidopsis thaliana to nutritional phosphorus deprivation
Author(s) -
Del Vecchio Hernan A.,
Ying Sheng,
Park Joonho,
Knowles Vicki L.,
Kanno Satomi,
Tanoi Keitaro,
She YiMin,
Plaxton William C.
Publication year - 2014
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.12663
Subject(s) - arabidopsis , mutant , phosphatase , complementation , arabidopsis thaliana , biology , microbiology and biotechnology , biochemistry , chemistry , enzyme , gene
Summary Plant purple acid phosphatases ( PAP s) 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) Arabidopsis thaliana suspension cells were purified and identified by MS as At PAP 12 (At2g27190), At PAP 25 (At4g36350) and At PAP 26 (At5g34850). At PAP 12 and At PAP 26 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. At PAP 25 exists as a 55 kD a monomer containing complex NX (S/T) glycosylation motifs at Asn172, Asn367 and Asn424. Transcript profiling and immunoblotting with anti‐At PAP 25 immune serum indicated that At PAP 25 is exclusively synthesized under −Pi conditions. Coupled with potent mixed‐type inhibition of At PAP 25 by Pi ( I 50 = 50 μ m ), this indicates a tight feedback control by Pi that prevents At PAP 25 from being synthesized or functioning as a phosphatase except when Pi levels are quite low. Promoter– GUS reporter assays revealed At PAP 25 expression in shoot vascular tissue of −Pi plants. Development of an atpap25 T‐ DNA insertion mutant was arrested during cultivation on soil lacking soluble Pi, but rescued upon Pi fertilization or complementation with At PAP 25 . Transcript profiling by quantitative RT ‐ PCR indicated that Pi starvation signaling was attenuated in the atpap25 mutant. At PAP 25 exhibited near‐optimal phosphatase activity with several phosphoproteins and phosphoamino acids as substrates. We hypothesize that At PAP 25 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.