title: Phosphatase under-producer mutants have altered phosphorus relations.
abstract: Phosphorus (P) acquisition and partitioning are essential for plant homeostasis. P is available for plant uptake when in its inorganic form (H2PO4-, or Pi), but Pi is often limiting in soils. Plants secrete acid phosphatases (APases) into the apoplastic space, which may be important for obtaining Pi from organic P sources; however, the relative importance of these enzymes for plant P nutrition has yet to be determined. We demonstrate that the root-associated APase pool is increased in Arabidopsis when Pi is limiting and document five APase isoforms secreted from Arabidopsis roots. Previously, we presented the identification of the phosphatase under-producer (pup) mutants, which have decreased in vivo root APase staining when grown under low P conditions. Here, we present the characterization of one of these, pup3, and further studies with pup1. pup3 has 49%, 38%, and 37% less specific APase activity in exudates, roots, and shoots, respectively. Root-associated APase activity is decreased by 16% in pup1 and 25% in pup3, regardless of P treatment. Two APase activity isoforms are reduced in pup3 exudates, and root and shoot isoforms are also affected. One of the two exudate isoforms is recognized by a polyclonal antibody raised to an Arabidopsis purple APase recombinant protein (AtPAP12); however, AtPAP12 transcript levels are unaffected in the mutant. The pup3 mutation was mapped to 68.4 +/- 6.0 centimorgans on chromosome 5. Although P concentrations were not altered in pup1 and pup3 tissues when grown in nutrient solution in which Pi was the sole source of P, the mutants had 10% (pup1) and 17% (pup3) lower shoot P concentrations when grown in a peat-vermiculite mix in which the majority of the total P was present as organic P. Therefore, the pup defects, which include secreted APases, are functionally important for plant P nutrition.
authors.affiliation: Intercollege Program in Plant Physiology, Penn State University, University Park, Pennsylvania 16802, USA. tomscha@email.unc.edu
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Tomscha
authors.forename: Melanie C
authors.initials: MC
authors.lastname: Trull
authors.forename: Jill
authors.initials: J
authors.lastname: Deikman
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Lynch
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Guiltinan
mesh_terms: D000135:Acid Phosphatase / Q000235:genetics* / Q000378:metabolism; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D002874:Chromosome Mapping; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D010758:Phosphorus / Q000378:metabolism*; D018517:Plant Roots / Q000201:enzymology / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; D007527:Isoenzymes; D010758:Phosphorus; D000135:Acid Phosphatase; C492223:purple acid phosphatase 12, Arabidopsis