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

¹College of Life Science and Chemical Engineering, Huaiyin Institute of Technology, Huaian, Jiangsu, 223003, People's Republic of China. ²College of Food Science and Technology, Nanjing Agricultural University, Nanjing, Jiangsu, 210095, People's Republic of China. ³Corresponding author. Phone: +86 0517 83591044. E-mail: baiqy@hyit.edu.cn, baiqy@hyit.edu.cn

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 Ca²⁺, along with lanthanum chloride (LaCl₃, a specific inhibitor of the Ca²⁺ pathway) and ethylene glycol tetraacetic acid (EGTA, a chelator of Ca²⁺) 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 Ca²⁺ application under NaCl stress further increased GAD activity and GABA content; the optimal concentration of Ca²⁺ for GAD activity and GABA accumulation was 5.0mM under 100mM 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 LaCl₃ or EGTA under NaCl stress. Our results suggest that salt stress combined with Ca²⁺ treatment may be used for preparation of millet with higher GABA content, which can be used as a natural resource for functional foods.