Abstract
When plants grow under low-P conditions, activities of external and internal acid phosphatase (APase) increase and contributes to P uptake and recycling, respectively. Proteaceae plants are well known as a low-P tolerant family, although the molecular mechanism has not been well understood. The aim of this study is to isolate and characterize APase homologs of Hakea laurina, which is a Proteaceae plant.
cDNAs for cluster roots of Hakea grown in low-P nutrient solution and a primer designed from conserved sequence among known APases were used for 3'-RACE. After sequencing for the clone library, 4 fragments for APase homologs were determined and designated as HlSAP1-4. These fragments were 40-76% similar to each other. HlSAP1 was identified most frequent from the library and shown the highest identity to an APase secreted from white lupin.
Localization of APase using a fluorogenic substrate was revealed that the higher APase activity was found in epidermis and root hairs of cluster roots. The activity of extracellular APase was dominant in cluster roots and contributed to P uptake from the rhizosphere.
