The ultimate goal of the project is to generate soybean germplasm with superior water use efficiency that will conserve soil moisture and improve productivity if the crop becomes water limited. Most of the water taken up by plant roots is lost via transpiration from small pores in leaves named stomata. However, to capture atmospheric CO2 which is essential for photosynthesis, stomatal pores need to stay open. In this project, we propose to modify stomatal opening in a smart way which will allow to limit the water loss under water-limited conditions with minimal effect on photosynthesis and stomatal behavior under well-watered conditions. We will achieve this by modifying the light-derived signal for stomata opening through increasing the amount of the photosynthesis-related protein which increases conversion of energy of light into heat. Our successful test of this approach in tobacco resulted in a 25% reduction of the amount of water used for each molecule of CO2 assimilated by leaf and increase in biomass accumulation under field conditions, limiting the wildtype growth. We expect that this manipulation will also be effective in soybean since overexpressed protein and its function is universal across higher plants. In the last three months, the beginning of the first year of this three-year project, we successfully initiated the transformation process to obtain lines of soybean with drought-inducible overexpression of photosynthesis-related protein. The genetic modification which is "switching on" only in response to the stressful conditions will work as an "insurance policy" against the drought related loss in yield. In the second and third years of this project, we will focus on evaluation of the effect of the introduced gene on soybean growth under water-limited conditions in greenhouse and field setups. The physiological and molecular analyses, together with observations of soybean development and yield estimation, will be used for comparative studies of modified lines and corresponding wildtype. The proposed research will be the first of its kind to examine the manipulation of chloroplast-derived signal for stomatal opening in response to light to improve water use efficiency in soybean. Novel bioengineering strategies to improve soybean are urgently needed, especially considering the long timelines for developing new crop varieties. Successful completion of this project has potential to increase the yield of soybean grown in Nebraska on 2.9 million rainfed acres and improve the soil moisture conservation in between irrigation cycles in the remaining 2.8 million irrigated acres.