AN EFFLUX TRANSPORTER OF SILICON IN RICE
|Year of Publication:||2011|
|Authors:||Jian Feng Ma1, Naoki Yamaji1,6, Namiki Mitani1,6, Kazunori Tamai1, Saeko Konishi2, Toru Fujiwara3,4, Maki Katsuhara1 & Masahiro Yano5|
Slicon is an important nutrient for the optimal growth and sustainable production of rice1, 2, 3, 4. Rice accumulates up to 10% silicon in the shoot, and this high accumulation is required to protect the plant from multiple abiotic and biotic stresses1, 2, 3, 4, 5. A gene, Lsi1, that encodes a silicon influx transporter has been identified in rice6. Here we describe a previously uncharacterized gene, low silicon rice 2 (Lsi2), which has no similarity to Lsi1. This gene is constitutively expressed in the roots. The protein encoded by this gene is localized, like Lsi1, on the plasma membrane of cells in both the exodermis and the endodermis, but in contrast to Lsi1, which is localized on the distal side, Lsi2 is localized on the proximal side of the same cells. Expression of Lsi2 in Xenopusoocytes did not result in influx transport activity for silicon, but preloading of the oocytes with silicon resulted in a release of silicon, indicating that Lsi2 is a silicon efflux transporter. The identification of this silicon transporter revealed a unique mechanism of nutrient transport in plants: having an influx transporter on one side and an efflux transporter on the other side of the cell to permit the effective transcellular transport of the nutrients.