Abstract
Rice (Oryza sativa) as a staple food, provides a major source of dietary selenium (Se) for humans, which essentially requires Se, however, the molecular mechanism for Se uptake is still poorly understood. Herein, we show evidence that the uptake of selenite, a main bioavailable form of Se in paddy soils, is mediated by a silicon (Si) influx transporter Lsi1 (OsNIP2;1) in rice. Defect of OsNIP2;1 resulted in a significant decrease in the Se concentration of the shoots and xylem sap when selenite was given. However, there was no difference in the Se concentration between the wild-type rice and mutant of OsNIP2;1 when selenate was supplied. A short-term uptake experiment showed that selenite uptake greatly increased with decreasing pH in the external solution. Si as silicic acid did not inhibit the Se uptake from selenite in both rice and yeast (Saccharomyces cerevisiae) at low pHs. Expression of OsNIP2;1 in yeast enhanced the selenite uptake at pH 3.5 and 5.5 but not at pH 7.5. On the other hand, defect of Si efflux transporter Lsi2 did not affect the uptake of Se either from selenite or selenate. Taken together, our results indicate that Si influx transporter OsNIP2;1 is permeable to selenite.
Highlights
Rice (Oryza sativa) as a staple food, provides a major source of dietary selenium (Se) for humans, which essentially requires Se, the molecular mechanism for Se uptake is still poorly understood
Plant PhysiologyÒ, August 2010, Vol 153, pp. 1871–1877, www.plantphysiol.org Ó 2010 American Society of Plant Biologists Downloaded from on October 5, 2020 - Published by www.plantphysiol.org centration decreased selenite uptake in different plant species (Broyer et al, 1972; Hopper and Parker, 1999)
A physiological study showed that selenite uptake by rice roots was inhibited by HgCl2 and AgNO3, suggesting that aquaporin is implicated in the uptake of selenite (Zhang et al, 2006)
Summary
Rice (Oryza sativa) as a staple food, provides a major source of dietary selenium (Se) for humans, which essentially requires Se, the molecular mechanism for Se uptake is still poorly understood. We show evidence that the uptake of selenite, a main bioavailable form of Se in paddy soils, is mediated by a silicon (Si) influx transporter Lsi (OsNIP2;1) in rice. Controlling Se uptake of plants from the environment (soils) will be important to decrease healthy risk of both toxicity and deficiency. It is still poorly understood how plants take up Se from the roots. Li et al (2008) reported that selenite uptake is at least partly to be mediated by phosphate transporters based on evidence that phosphorus deficiency enhanced selenite uptake in wheat This is supported by earlier works, which reported that increasing phosphate con-. We found that different from Si and arsenite, Lsi, an efflux transporter of Si (Ma et al, 2007), is not involved in the transport of selenite
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