A Bio-inspired Synthetic Gene Circuit revised title: A synthetic gene circuit confers salt tolerance in plants

Soil salinity exerts a major constraint on global crop production, while seawater intrusion impacts coastal aquifers and surface waters. Using a blueprint from nature, we designed and implemented genetically encoded circuits that confer high salt tolerance to Arabidopsis and rice plants. Endodermal-like barriers, duplicated to the root epidermis and distally expanded to protect sensitive regions, provide tolerance to salinity levels comparable to seawater. Two additional genetic modules were added to reduce adverse effects of the epidermal barriers on ion uptake (aquaporin module) and to provide osmotic protection (osmolyte module). Arabidopsis and rice containing all three genetic modules can grow with continuous 600 mM NaCl treatment for extended days and reproduce. Transcriptomic analysis suggests that our rational engineering approach primes plants for salt tolerance, even without salt exposure, while detailed ionic analysis uncovers leakage suggesting means for improvement. Our results, duplicating suberin and the Casparian Strip in the epidermis while addressing adverse effects and osmotic stress demonstrate a new approach to enhancing salt tolerance while offering additional insights into plant responses to high salinity.