The Role of SIPIP1;7in Improving Photosynthetic Efficiency, Root Water Uptake, and Salt Stress Tolerance of Tomato

Plasma-membrane intrinsic proteins (PIPS) play important regulatory roles in plant growth and development, and in the maintenance of water homeostasis under stress conditions. To investigate the function of SlPIP1;7 in tomato (Solanum lycopersicum) plants, we created transgenic tomato lines in which the SlPIP1;7 gene was overexpressed or silenced. SlPIP1;7-overexpressing and SlPIP1;7-silenced plants were taller and shorter than wild-type plants, respectively. Additionally, silenced lines had a significantly narrower stem diameter than wild-type plants and severely retarded shoot and root growth, suggesting that overexpression of SlPIP1;7 enhances tomato growth. Moreover, SlPIP1;7-overexpressing plants exhibited increased salt stress tolerance, while SlPIP1;7-silenced plants were more sensitive to salt stress. SlPIP1;7-overexpressing plants showed a higher photosynthetic rate and root hydraulic conductivity, less electrolyte leakage, and less malondialdehyde and reactive oxygen species accumulation under salt stress compared to the wild-type; SlPIP1;7-silenced plants showed the opposite tendencies. These results suggest that overexpression ofSlPIP1;7 promotes photosynthetic efficiency, root water uptake, and antioxidant defense in plants under salt stress, thereby imparting salt tolerance. SlPIP1;7 is thus a valuable genetic resource to enhance stress tolerance in tomato plants.