M. Nishikoori et al., Cloning and characterization of cDNA of the GPI-anchored purple acid phosphatase and its root tissue distribution in Spirodela oligorrhiza, PHYSL PLANT, 113(2), 2001, pp. 241-248
A cDNA clone of the glycosylphosphatidylinositol (GPI)-anchored purple acid
phosphatase (PAP) has been obtained by a combination of cDNA library scree
ning and 5' rapid amplification of cDNA ends from Spirodela oligorrhiza pla
nts grown under phosphate-deficient ( - P) conditions. The open reading fra
me of the S. oligorrhiza PAP cDNA consists of 1365 bp encoding a 455 amino
acid protein. Its deduced amino acid sequence shows 82 and 80% similarity t
o Arabidopsis thaliana and Phaseolus vulgaris PAP, respectively. The amino
acid residue, Ala439, followed by two more small amino acid residues, Asp a
nd Ser, is predicted to be the GPI-anchoring (omega) site. The absence of a
dibasic motif upstream of the putative omega site suggests that the PAP is
a cell wall protein. This presumption is supported by the finding that PAP
was released by digestion of the cell wall fraction with cellulase. The GP
I anchor is speculated to be a signal for transporting PAP to the cell wall
. Immunohistochemical results using - P plant roots demonstrate that PAP is
preferentially distributed in the outermost cortical cells of roots but no
t in the epidermis, suggesting its role in acquiring inorganic phosphate un
der phosphate-deficient conditions. Northern blot analysis using the S. oli
gorrhiza PAP cDNA as a probe demonstrates that expression of the PAP gene i
ncreased during growth of - P plants and this time-dependent occurrence in
mRNA levels of the PAP in - P plants was also observed in their protein and
activity levels.