Cell wall proteins in white clover: influence of plant phosphate status

White clover (Trifolium repens L.) plants were grown in either P-containing liquid media, or in media with the sole source of phosphate removed (P-deprived). At 29 d, plants were harvested and a water-soluble whole tissue extract and an ionically-bound (1 M salt-extractable) cell wall protein extract made from root and leaf tissue. Acid phosphatase activity was highest in all extracts from root and leaf tissue excised from P-deprived plants, with the biggest difference (4.5-fold) in root cell walls. The smallest fold-increase was observed in the leaf water-soluble extract. The relative intensity of several, although not all, acid phosphatase isoenzymes was also highest in extracts from P-deprived plants. Up to the limits of detection used, no new acid phosphatase isoenzymes could be detected in extracts from plants maintained either in P-deprived or P-containing media. The complement of ionically-bound (1 M salt-extractable) cell wall glycoproteins in leaf and root tissue extracts maintained in P-deprived and P-containing media was also compared. Using SDS-PAGE and immuno-recognition with mAb 2.23, a monoclonal antibody that specifically recognises xylose/fucose mixed-type N-linked glycans, glycoproteins of 30 and 31 kDa were identified which were more prevalent in the P-deprived root cell wall. Further, a protein of 60 kDa was identified, which was prevalent in root cell wall extracts from plants maintained in P-containing media. The GNA lectin, which detects oligomannose N-linked structures, identified a glycoprotein of 37 kDa which was more prevalent in the P-deprived root cell wall.