Role of OsLsi1 polarity in Si uptake and accumulation in rice. A) Transport activity of Flag-OsLsi1 variants for Ge in oocytes. Oocytes expressing Flag-OsLsi1, Flag-OsLsi1^I285A, or Flag-OsLsi1^{I18, 285A} were exposed to MBS with 1 mM GeO₂ for 30 min. The Ge concentration in the oocytes was determined. Data are means ± Sd (n = 4). B to D) Expression levels of OsLsi1 in the roots B), short-term Si uptake C), and Si accumulation in the shoot D) of transgenic plants carrying Flag-OsLsi1, Flag-OsLsi1^I285A or Flag-OsLsi1^{I18, 285A} encoding polar and nonpolar OsLsi1, respectively. For the short-term Si uptake experiment in C), transgenic seedlings (22-d-old), as well as wild-type (WT) rice and lsi1-3 mutant, were exposed to a solution containing 0.5 mM Si for 8 h. At the end of the experiment, the roots were harvested for mRNA extraction and determination of OsLsi1 expression level B). For Si accumulation comparison C), transgenic seedlings (16-d-old) were exposed to a solution containing 1 mM Si. After 7 d, the shoots were sampled for Si determination. Vertical bars represent the Sd of 4 biological replicates. Different letters indicate significant differences at P < 0.05 by Tukey–Kramer's test.