Salt Stress Induces Accumulation of γ–Aminobutyric Acid in Germinated Foxtail Millet (Setaria italica L.)

ABSTRACT Effects of NaCl treatments on sprout length, the contents of soluble protein, free amino acids, and γ‐aminobutyric acid (GABA) and on glutamate decarboxylase (GAD) activity in germinated foxtail millet were investigated, and the regulating effects of exogenous Ca 2+ , along with lanthanum chloride (LaCl 3 , a specific inhibitor of the Ca 2+ pathway) and ethylene glycol tetraacetic acid (EGTA, a chelator of Ca 2+ ) under salt stress, on GABA accumulation in germinated millet were examined in this paper. The results showed that NaCl treatments caused a decrease in sprout length of millet. Low concentration of NaCl treatments increased soluble protein content, but high concentration decreased soluble protein content. The level of free amino acids, GAD activity, and GABA content increased significantly under NaCl stress. Exogenous Ca 2+ application under NaCl stress further increased GAD activity and GABA content; the optimal concentration of Ca 2+ for GAD activity and GABA accumulation was 5.0m M under 100m M NaCl for 48 hr, at which GABA content was 31.92 mg/100 g, a 1.41‐fold increase as compared with that in seeds under NaCl stress (22.64 mg/100 g). GAD activity and GABA accumulation in germinated millet decreased when treated with LaCl 3 or EGTA under NaCl stress. Our results suggest that salt stress combined with Ca 2+ treatment may be used for preparation of millet with higher GABA content, which can be used as a natural resource for functional foods.