Secretion of beta-propeller phytase from tobacco and Arabidopsis roots enhances phosphorus utilization

Abstract A large proportion of soil phosphorus (P) exists as organic compounds, of which phytic acid (IHP) is the dominant form. To generate transgenic plants capable of utilizing exogenous IHP, β-propeller phytase from Bacillus subtilis ( 168phyA ) was constitutively expressed in tobacco and Arabidopsis , and was shown to be secreted from their roots. In tobacco, phytase activities in transgenic leaf and root extracts were seven to nine times higher than those in wild-type extracts; whereas, the extracellular phytase activities of transgenic plants were enhanced by four to six times. In sterile hydroponic culture using 1 mM Na-IHP as the sole P source, the transgenic tobacco lines accumulated 1.7–2.2 times more shoot biomass than the wild-type plants after 30 days of growth, concomitant with a 27–36% increase in shoot P concentration. Similar results were observed from the transgenic Arabidopsis . Our work on the exudation of recombinant Bacillus phytase from plant roots may offer a new perspective on mobilizing soil phytate into inorganic phosphate for plant uptake.