Investigating the Contribution of the Phosphate Transport Pathway to Arsenic Accumulation in Rice

• Published in: Plant physiology (Bethesda) 2011-09, Vol.157 (1), p.498-508
• Main Authors: Wu, Zhongchang, Ren, Hongyan, McGrath, Steve P., Wu, Ping, Zhao, Fang-Jie
• Format: Article
• Language: English
• Subjects: Arsenates; Arsenic; Arsenic - metabolism; Arsenites; Biological and medical sciences; cacodylic acid; exposure duration; flooded conditions; Flooded soils; Fundamental and applied biological sciences. Psychology; genetics; Grains; Ion Transport; metabolism; mutants; Mutation; Oryza; Oryza - genetics; Oryza - metabolism; Oryza sativa; paddy soils; phosphates; Phosphates - metabolism; Plant physiology and development; Plant Roots; Plant Roots - metabolism; Plant Shoots; Plant Shoots - metabolism; Plants; Rice; risk; roots; sap; shoots; Speciation; starvation; transcription factors; transporters; WHOLE PLANT AND ECOPHYSIOLOGY; Xylem
• ISSN: 0032-0889; 1532-2548; 1532-2548
• DOI: 10.1104/pp.111.178921

Arsenic (As) accumulation in rice (Oryza sativa) may pose a significant health risk to consumers. Plants take up different As species using various pathways. Here, we investigated the contribution of the phosphate (Pi) transport pathway to As accumulation in rice grown hydroponically or under flooded soil conditions. In hydroponic experiments, a rice mutant defective in OsPHFl (for phosphate transporter traffic facilitator1) lost much of the ability to take up Pi and arsenate and to transport them from roots to shoots, whereas transgenic rice overexpressing either the Pi transporter OsPhtl;8 (OsPT8) or the transcription factor OsPHR2 (for phosphate starvation response2) had enhanced abilities of Pi and arsenate uptake and translocation. OsPT8 was found to have a high affinity for both Pi and arsenate, and its overexpression increased the maximum influx by 3-to 5-fold. In arsenate-treated plants, both arsenate and arsenite were detected in the xylem sap, with the proportion of the latter increasing with the exposure time. Under the flooded soil conditions, the phfl mutant took up less Pi whereas the overexpression lines took up more Pi. But there were no similar effects on As accumulation and distribution. Rice grain contained predominantly dimethylarsinic acid and arsenite, with arsenate being a minor species. These results suggest that the Pi transport pathway contributed little to As uptake and transport to grain in rice plants grown in flooded soil. Transgenic approaches to enhance Pi acquisition from paddy soil through the overexpression of Pi transporters may not increase As accumulation in rice grain.