Novel Phytase from Pteris vittata Resistant to Arsenate, High Temperature, and Soil Deactivation

Abstract

Arsenate interferes with enzymatic processes and inhibits inorganic phosphorus (Pi) uptake in many plants. This study examined the role of phytase and phosphatase in arsenate tolerance and phosphorus (P) acquisition in the arsenic hyperaccumulator Pteris vittata . Enzyme-mediated hydrolysis of phytate in P. vittata extracts was not inhibited by arsenate at 5 mM or by heating at 100 °C for 10 min. Root exudates of P. vittata exhibited the highest phytase activity (18 nmol Pi mg(-1) protein min(-1)) when available P was low, allowing its growth on media amended with phytate as the sole source of P. Phosphorus concentration in P. vittata gametophyte tissue grown on phytate was equivalent to plants grown with inorganic phosphate at 2208 mg kg(-1), and arsenic was increased from 1777 to 2630 mg kg(-1). After 2 h of mixing with three soils, P. vittata phytase retained more activity, decreasing from ∼ 26 to ∼ 25 nmol Pi mg(-1) protein min(-1), whereas those from Pteris ensiformis and wheat decreased from ∼ 18 to ∼ 1 nmol Pi mg(-1) protein min(-1). These results suggest P. vittata has a uniquely stable phytase enabling its P acquisition in P-limiting soil environments. Furthermore, the P. vittata phytase has potential use as a soil amendment, a transgenic tool, or as a feed additive supplement, reducing the need for nonrenewable, polluting P fertilizers.