Fig. 7.

Effect of shoot Si accumulation on expression of OsHMA2, OsHMA3, and OsNramp5 in the rice roots. A split root experiment was conducted by splitting the roots of seedlings (18 d old) without Si into two parts. Half roots were exposed to 1 mM Si (+Si) (right) and the other half to 0 mM Si (–Si) (left) in a separate compartment. Split roots exposed to –Si or +Si in both compartments were used as controls. After a 7-d culture, all the roots were exposed to 1 µM Cd for 24 h in the presence or absence of Si as pre-culture and the roots in different compartments were separately sampled for RNA extraction. The expression of OsHMA2 (A), OsHMA3 (B), and OsNramp5 (C) was determined by quantitative RT-PCR. HistoneH3 was used as an internal standard. Expression relative to –Si roots (left) is shown. Data are the means±SD (n=4). Different lower-case letters indicate significant difference at P<0.05 by Duncan’s test.