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

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.