TsMIP6 enhances the tolerance of transgenic rice to salt stress and interacts with target proteins

Aquaporins (AQPs), a large family of channel proteins in plants, play an important role in regulating the balance of osmotic potential in cells. We isolated an AQP gene, TsMIP6, from the halophyte Thellungiella salsuginea and functionally characterized it in transgenic rice (Oryza sativa). This gene belongs to a subfamily of tonoplast intrinsic proteins and is localized at the plasma membrane. Real-time PCR showed that expression of TsMIP6 in shoots or roots of T. salsuginea was markedly induced by salinity, whereas its ectopic expression in ‘Kitaake’ lines of rice significantly increased plant tolerance to salt stress. Physiological data suggested that TsMIP6 is involved in regulating ion homeostasis and water channel activity in salt-stressed transgenic rice. Heterologous expression analysis indicated that TsMIP6 specifically interacts with a member of the glycoside hydrolase family 64 protein #617 in yeast cells. This suggests that the relationship between TsMIP6 and #617 has a crucial role in mediating osmotic balance in plant cells. Moreover, TsMIP6 might help to modulate the transport of some neutral molecules and may function through a pathway regulating solute equilibrium to maintain osmotic potential.