Biosynthesis and accumulation of GABA in rice plants treated with acetic acid.

Rice seedlings () that have died from drought cannot be rescued by watering afterward, but pre-treatment with exogenous acetic acid enabled the plants to produce shoots again after being watered (hereinafter referred to as "drought resilience"). To elucidate the metabolism of acetic acid, we treated rice plants with C-labeled acetic acid and traced C-labeled metabolites using LC-MS and C-NMR techniques. The LC-MS and C-NMR spectral data of the root extracts indicated that the acetic acid treatment was absorbed into the plants and then was metabolized to gamma-aminobutyric acid (GABA) by glutamic acid decarboxylase (GAD). GABA accumulation in the roots took place in advance of that in the shoots, and the survival rate against drought stress increased in proportion to the amount of GABA accumulated in the shoots. Therefore, GABA accumulation in shoots may be a key step in drought resilience induced by the acetic acid treatment.