The role of the rice aquaporin Lsi1 in arsenite efflux from roots
Article first published online: 16 FEB 2010
© The Authors (2010). Journal compilation © New Phytologist Trust (2010)
Volume 186, Issue 2, pages 392–399, April 2010
How to Cite
Zhao, F.-J., Ago, Y., Mitani, N., Li, R.-Y., Su, Y.-H., Yamaji, N., McGrath, S. P. and Ma, J. F. (2010), The role of the rice aquaporin Lsi1 in arsenite efflux from roots. New Phytologist, 186: 392–399. doi: 10.1111/j.1469-8137.2010.03192.x
- Issue published online: 25 MAR 2010
- Article first published online: 16 FEB 2010
- Received: 5 November 2009, Accepted: 14 December 2009
- arsenic accumulation;
- arsenite (As(III)) efflux;
- silicon transporter
- •When supplied with arsenate (As(V)), plant roots extrude a substantial amount of arsenite (As(III)) to the external medium through as yet unidentified pathways. The rice (Oryza sativa) silicon transporter Lsi1 (OsNIP2;1, an aquaporin channel) is the major entry route of arsenite into rice roots. Whether Lsi1 also mediates arsenite efflux was investigated.
- •Expression of Lsi1 in Xenopus laevis oocytes enhanced arsenite efflux, indicating that Lsi1 facilitates arsenite transport bidirectionally.
- •Arsenite was the predominant arsenic species in arsenate-exposed rice plants. During 24-h exposure to 5 μm arsenate, rice roots extruded arsenite to the external medium rapidly, accounting for 60–90% of the arsenate uptake. A rice mutant defective in Lsi1 (lsi1) extruded significantly less arsenite than the wild-type rice and, as a result, accumulated more arsenite in the roots. By contrast, Lsi2 mutation had little effect on arsenite efflux to the external medium.
- •We conclude that Lsi1 plays a role in arsenite efflux in rice roots exposed to arsenate. However, this pathway accounts for only 15–20% of the total efflux, suggesting the existence of other efflux transporters.