Trehalose accumulation in rice plants confers high tolerance levels to different abiotic stresses

TLDR

Trehalose is a compatible solute that stabilizes biological structures under abiotic stress in microbes, but it is generally absent in most plants except resurrection species. The study aims to enhance rice tolerance to abiotic stresses by overexpressing a fusion of Escherichia coli trehalose biosynthetic genes otsA and otsB. A single transformation event introduces the fusion gene under tissue‑specific or stress‑dependent promoters, yielding higher catalytic efficiency for trehalose synthesis. Transgenic rice lines exhibit sustained growth, reduced photo‑oxidative damage, improved mineral balance, and 3–10‑fold trehalose accumulation under salt, drought, and cold, correlating with higher soluble carbohydrates and photosynthetic capacity, thereby proving the feasibility of engineering stress tolerance and productivity.

Abstract

Trehalose is a nonreducing disaccharide of glucose that functions as a compatible solute in the stabilization of biological structures under abiotic stress in bacteria, fungi, and invertebrates. With the notable exception of the desiccation-tolerant “resurrection plants,” trehalose is not thought to accumulate to detectable levels in most plants. We report here the regulated overexpression of Escherichia coli trehalose biosynthetic genes ( otsA and otsB ) as a fusion gene for manipulating abiotic stress tolerance in rice. The fusion gene has the advantages of necessitating only a single transformation event and a higher net catalytic efficiency for trehalose formation. The expression of the transgene was under the control of either tissue-specific or stress-dependent promoters. Compared with nontransgenic rice, several independent transgenic lines exhibited sustained plant growth, less photo-oxidative damage, and more favorable mineral balance under salt, drought, and low-temperature stress conditions. Depending on growth conditions, the transgenic rice plants accumulate trehalose at levels 3–10 times that of the nontransgenic controls. The observation that peak trehalose levels remain well below 1 mg/g fresh weight indicates that the primary effect of trehalose is not as a compatible solute. Rather, increased trehalose accumulation correlates with higher soluble carbohydrate levels and an elevated capacity for photosynthesis under both stress and nonstress conditions, consistent with a suggested role in modulating sugar sensing and carbohydrate metabolism. These findings demonstrate the feasibility of engineering rice for increased tolerance of abiotic stress and enhanced productivity through tissue-specific or stress-dependent overproduction of trehalose.