Invited Review

Pflügers Archiv - European Journal of Physiology

, Volume 456, Issue 4, pp 679-686

First online:

Characterization of substrate specificity of a rice silicon transporter, Lsi1

  • Namiki MitaniAffiliated withResearch Institute for Bioresources, Okayama University
  • , Naoki YamajiAffiliated withResearch Institute for Bioresources, Okayama University
  • , Jian Feng MaAffiliated withResearch Institute for Bioresources, Okayama University Email author 

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Abstract

Lsi1 (OsNIP2;1) is the first silicon (silicic acid) transporter identified in plant, which belongs to the nodulin 26-like intrinsic membrane protein (NIP) subfamily. In this study, we characterized the function of this transporter by using the Xenopus laevis oocyte expression system. The transport activity of Lsi1 for silicic acid was significantly inhibited by HgCl2 but not by low temperature. Lsi1 also showed an efflux transport activity for silicic acid. The substrate specificity study showed that Lsi1 was able to transport urea and boric acid; however, the transport activity for silicic acid was not affected by the presence of equimolar urea and was decreased only slightly by boric acid. Furthermore, among the NIPs subgroup, OsNIP2;2 showed transport activity for silicic acid, whereas OsNIP1;1 and OsNIP3;1 did not. We propose that Lsi1 and its close homologues form a unique subgroup of NIP with a distinct ar/R selectivity filter, which is located in the narrowest region on the extra-membrane mouth and govern the substrate specificity of the pore.

Keywords

Silicon Rice Aquaporin NIP subfamily Substrate specificity Phosphorylation ar/R selectivity filter