Phytate and Arsenic Enhance Each Other’s Uptake in As-hyperaccumulator <i>Pteris vittata</i>: Root Exudation of Phytate and Phytase, and Plant Uptake of Phytate-P
Ran Han, Jiayi Chen, Si-Xue He, Chenjing Liu, Zhihua Dai, Xue Liu, Yue Cao, Q. Lena
Abstract
Phytate as a root exudate is rare in plants as it mainly serves as a P storage in the seeds; however, As-hyperaccumulator Pteris vittata effectively secretes phytate and utilizes phytate-P, especially under As exposure. This study investigated the effects of As on its phytate and phytase exudation and the impacts of As and/or phytate on each other’s uptake in P. vittata through two hydroponic experiments. Under 10–100 μM arsenate (AsV), the exudation of phytate and phytase by P. vittata was increased by 50–72% to 20.4–23.4 μmol h–1 g–1 and by 28–104% to 18.6–29.5 nmol h–1 plant–1, but they were undetected in non-hyperaccumulator Pteris ensiformis at 10 μM AsV. Furthermore, compared to 500 μM phytate, the phytate concentration in the growth media was reduced by 69% to 155 μM, whereas the P and As contents in P. vittata fronds and roots were enhanced by 68–134% and 44–81% to 2423–2954 and 82–407 mg kg–1 under 500 μM phytate plus 50 μM AsV. The increased P/As uptake in P. vittata was probably attributed to 3.0–4.5-fold increase in expressions of P transporters PvPht1;3–1;4. Besides, under As exposure, plant P may be converted to phytate in P. vittata roots, thereby increasing phytate’s contents by 84% to 840 mg kg–1. Overall, our results suggest that As-induced phytate/phytase exudation and phytate-P uptake stimulate its growth and As hyperaccumulation by P. vittata.