title: Molecular and biochemical characterization of AtPAP15, a purple acid phosphatase with phytase activity, in Arabidopsis.
abstract: Purple acid phosphatase (PAP) catalyzes the hydrolysis of phosphate monoesters and anhydrides to release phosphate within an acidic pH range. Among the 29 PAP-like proteins in Arabidopsis (Arabidopsis thaliana), AtPAP15 (At3g07130) displays a greater degree of amino acid identity with soybean (Glycine max; GmPHY) and tobacco (Nicotiana tabacum) PAP (NtPAP) with phytase activity than the other AtPAPs. In this study, transgenic Arabidopsis that expressed an AtPAP15 promoterbeta-glucuronidase (GUS) fusion protein showed that AtPAP15 expression was developmentally and temporally regulated, with strong GUS staining at the early stages of seedling growth and pollen germination. The expression was also organ/tissue specific, with strongest GUS staining in the vasculature, pollen grains, and roots. The recombinant AtPAP purified from transgenic tobacco exhibited broad substrate specificity with moderate phytase activity. AtPAP15 T-DNA insertion lines exhibited a lower phytase and phosphatase activity in seedling and germinating pollen and lower pollen germination rate compared with the wild type and their complementation lines. Therefore, AtPAP15 likely mobilizes phosphorus reserves in plants, particularly during seed and pollen germination. Since AtPAP15 is not expressed in the root hair or in the epidermal cells, it is unlikely to play any role in external phosphorus assimilation.
authors.affiliation: School of Biological Sciences, University of Hong Kong, Pokfulam, Hong Kong, China.
authors.forename: Ruibin
authors.initials: R
authors.lastname: Kuang
authors.forename: Kam-Ho
authors.initials: KH
authors.lastname: Chan
authors.forename: Edward
authors.initials: E
authors.lastname: Yeung
authors.forename: Boon Leong
authors.initials: BL
authors.lastname: Lim
mesh_terms: D000135:Acid Phosphatase / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D005816:Genetic Complementation Test; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism*; D016254:Mutagenesis, Insertional; D009154:Mutation; D030821:Plants, Genetically Modified; D013379:Substrate Specificity; D014026:Nicotiana / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; D004269:DNA, Bacterial; D009097:Multienzyme Complexes; C036483:T-DNA; C529220:PAP15 protein, Arabidopsis; D000135:Acid Phosphatase