Expression of tomato SlTIP2;2 enhances the tolerance to salt stress in the transgenic Arabidopsis and interacts with target proteins

Three independent transgenic Arabidopsis lines expressing SlTIP2;2 from Solanum lycopersicum L. cv. Lichun under the control of its endogenous promoter were used to analyze the expression of SlTIP2;2 and the salt stress tolerance under NaCl concentration gradient treatment. The expression patterns of SlTIP2;2 were shown to be tissue-specific and NaCl dose-dependent under salt stress. SlTIP2;2-transformed Arabidopsis plants exhibited enhanced salt stress tolerance, and the physiological parameters suggested that SlTIP2;2 has close links with the ion homeostasis and antioxidant enzymes activities in salt-stressed transgenic Arabidopsis. Moreover, SlTIP2;2 expression significantly affected the Na⁺ and K⁺ fluxes from the root meristematic zones and resulted in remarkable changes in the morphology of the pith ray cells in the inflorescence stems of transgenic Arabidopsis. Based on the yeast growth assay, β-galactosidase activity testing and bimolecular fluorescence complementation, SlTIP1;1, SlTIP2;1 and an UDP-galactose transporter were confirmed to interact with SlTIP2;2, which may greatly broaden our understanding of the physiological functions of aquaporins.