Abstract
Silicon is a beneficial element for plant growth and all plants contain a significant amount of Si in their body. However, the molecular mechanism underlying silicon uptake is poorly understood. Recently, we cloned two genes (Lsi1 and Lsi2) which are responsible for Si uptake in rice mutants defective in Si uptake. In the present study, the functional analysis of Lsi2 was conducted. Lsi2 was constitively expressed in the roots and the expression was decreased by Si supply. Experiment with GFP fusion shows that the protein is localized at the plasma membrane of onion epidermal cells. In situ hybridization and immunostaining revealed that Lsi2 was localized at both exodermis and endodermis where Casparian strips are located. Furthermore, in contrast to Lsi1, Lsi2 was localized in inner side of those cells. Taken together, our results indicate that Lsi2 is a transporter responsible for efflux of Si from the cells.
