Submitted to: American Society of Plant Physiologists Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 7/17/2000
Publication Date: N/A
Technical Abstract: White lupin when subjected to a low phosphorus (P) environment forms proteoid (cluster) roots. Proteoid roots from P-stressed plants exude organic acids and acid phosphatase (APase) enzyme as a strategy to acquire unavailable P. We have isolated an APase cDNA clone that is highly expressed in P-stressed proteoid roots but not in other tissues. This white elupin APase cDNA clone is 1532 bps in length with an ORF of 1380 bp. The 460 amino acid lupin APase polypeptide shows good similarity with the purple APases of arabidopsis and bean. In order to establish if this APase cDNA encoded the APase enzyme exuded from P-stressed proteoid roots, we purified the exuded APase and determined its N terminal amino acid sequence. Amino acid residues 32-41 of the deduced APase polypeptide were a direct match with the 10 N terminal amino acids of the exuded enzyme. These data demonstrate that we have in fact isolated the cDNA encoding the P- stress induced APase exuded from proteoid roots. The processed, exuded enzyme is comprised of 429 AA with a presequence of 31 AA. PSORT analysis of the 31 AA presequence targets the protein to the outside of the cell with a .82 certainty. Antibodies have been produced to lupin P-stress exuded APase for cellular localization studies. In addition, the 5'- upstream region of the lupin APase gene has been isolated.