Distribution Pattern of Silicon Transporters in Maize Seedling

The relationship between relative expression of three Si transporters (Lsi1, Lsi2 and Lsi6) genes and Si contents, in four different segments of maize seedling: basal, apical parts of seminal roots, leaf sheaths, and blades under Si concentrations (0, 2 and 10 mM) was investigated. The results indicated that under the control conditions, Si content in aerial parts and roots of seedlings were identical but under 2 and 10 mM Si concentrations, its content in the aerial parts was higher than the roots. Silicon uptake by maize seedlings was not proportional to the increase of its supply. Unexpectedly, the Si content of maize seedlings did not increase when the Si supply increased to 10. The results also showed that under normal conditions, relative expression of ZmLsi1 and ZmLsi2 in shoots of maize seedlings was significantly higher than roots, while ZmLsi6 was mainly expressed in leaf sheaths. Application of Si significantly increased all three silicon transporter expressions. Among these transporters, the response of Lsi2 was discriminative to the external Si concentration such that under 10 mM Si, the expression of Lsi2 was more noticeable. The results suggested that Lsi2 may have a role in efflux of Si in maize under high concentration of external Si.