Involvement of Silicon Influx Transporter OsNIP2;1 in Selenite Uptake in Rice    

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.

Interactive effects of different inorganic As and Se species on their uptake and translocation by rice (Oryza sativa L.) seedlings

“…However, improvement rather than antagonism were observed for the uptake into root. The antagonistic interaction between As(III) and Se(IV) in rice was not observed by Zhao et al (2010) either. The exact mechanisms on these are still unknown.…”

“…It is generally accepted that the As(III) influx in rice root through silicon influx transporters OsNIP2;1 . Zhao et al (2010) clearly showed that this transporter is permeable to Se(IV). It seemed that antagonistic interaction between As(III) and Se(IV) would exist because they share the same transporter (Si transporter).…”

“…Arsenite is transported into rice by aquaporins (Meharg and Jardine 2003), such as silicon transporters . Interestingly, the uptake of Se(IV) is mediated by a silicon (Si) influx transporter Lsi1 in rice as well (Zhao et al 2010). Therefore, competition between As(III) and Se(IV) uptake is likely present through silicon transporters.…”

Sodium selenite treatment of vegetable seeds and seedlings and the effect on antioxidant status

“…Selenate is absorbed through a transport process coupled to a H + -ATPase, with the help of a sulfate (Terry et al, 2000) or silicon transporter (Zhao et al, 2010); once absorbed by the plants, maintains the inorganic form (De Souza et al, 1998;Cartes et al, 2006). In contrast, the absorption of selenite occurs in a different way (Terry et al, 2000), through a phosphate transporter (Zhao et al, 2010).…”

Role of aquaporins in cell proliferation: What else beyond water permeability?

“…12,[38][39][40] In addition, several metabolically important small neutral solutes and ions have been identified as AQP substrates, namely hydrogen peroxide (H 2 O 2 ). 13,17,41,42 carbon dioxide, 43,44 nitric oxide, 45,46 ammonia, 47,48 metalloids such as arsenite and antimonite, 49-51 selenite, 52 boric acid, 53 and silicic acid. 51 AQP6 with low intrinsic water permeability may function primarily as an anion transporter.…”