The study investigates the effects of overexpressing trehalose biosynthetic genes in rice to enhance abiotic stress tolerance. Trehalose, a nonreducing disaccharide, functions as a compatible solute in various organisms to stabilize biological structures under stress conditions. The researchers used a fusion gene of Escherichia coli trehalose biosynthetic genes (otsA and otsB) under tissue-specific or stress-dependent promoters to manipulate abiotic stress tolerance in rice. Compared to nontransgenic rice, several independent transgenic lines exhibited sustained plant growth, reduced photo-oxidative damage, and more favorable mineral balance under salt, drought, and low-temperature stress conditions. The transgenic rice plants accumulated trehalose at levels 3-10 times higher than nontransgenic controls, but peak levels remained below 1 mg/g fresh weight, suggesting that trehalose's primary effect is not as a compatible solute. Instead, increased trehalose accumulation correlated with higher soluble carbohydrate levels and an elevated capacity for photosynthesis under both stress and nonstress conditions. These findings demonstrate the feasibility of engineering rice for increased tolerance to abiotic stress and enhanced productivity through tissue-specific or stress-dependent overproduction of trehalose.The study investigates the effects of overexpressing trehalose biosynthetic genes in rice to enhance abiotic stress tolerance. Trehalose, a nonreducing disaccharide, functions as a compatible solute in various organisms to stabilize biological structures under stress conditions. The researchers used a fusion gene of Escherichia coli trehalose biosynthetic genes (otsA and otsB) under tissue-specific or stress-dependent promoters to manipulate abiotic stress tolerance in rice. Compared to nontransgenic rice, several independent transgenic lines exhibited sustained plant growth, reduced photo-oxidative damage, and more favorable mineral balance under salt, drought, and low-temperature stress conditions. The transgenic rice plants accumulated trehalose at levels 3-10 times higher than nontransgenic controls, but peak levels remained below 1 mg/g fresh weight, suggesting that trehalose's primary effect is not as a compatible solute. Instead, increased trehalose accumulation correlated with higher soluble carbohydrate levels and an elevated capacity for photosynthesis under both stress and nonstress conditions. These findings demonstrate the feasibility of engineering rice for increased tolerance to abiotic stress and enhanced productivity through tissue-specific or stress-dependent overproduction of trehalose.