Abstract
We investigated the effects of exogenous spermidine (Spd) on the physiological status, γ-aminobutyric acid (GABA) synthase activity, and gene expressions in germinating soybeans under NaCl stress. The results show that Spd significantly increases sprout growth and biomass, decreases malonaldehyde and H2O2 contents, and markedly promotes the activities of superoxide dismutase, catalase, peroxidase, and glutathione peroxidase of germinating soybeans. The harmful effect of NaCl stress was alleviated by exogenous Spd. GABA accumulation in germinating soybeans was caused by the activation of diamine oxidase, polyamine oxidase, aminoaldehyde dehydrogenase, and glutamate decarboxylase activities and by up-regulating their gene expression under Spd-NaCl treatment. The GABA content decreased by 57% and 46% in germinating soybeans with the application of aminoguanidine under Spd and Spd-NaCl treatments, respectively. In conclusion, spermidine induces the accumulation of GABA and increases sprouts biomass, thereby enhancing the functional quality of germinating soybeans.
Highlights
Gamma-aminobutyric acid (GABA), a four-carbon non-protein amino acid, is a major inhibitory neurotransmitter in the mammalian brain [1]
Compared with the control and NaCl treatment, the GABA content in four-day germinating soybeans under Spd-NaCl treatment increased by 116% and 73% compared with the control and increased by 42% and 74% compared with the NaCl treatment, respectively (Figure 4)
NaCl ctreatment, theb GABA content in fourday germinating soybeans under Spd-NaCl treatment increased by 116% and 73% compared with the control and increased by 42% and 74% compared with the NaCl treatment, respectively
Summary
Gamma-aminobutyric acid (GABA), a four-carbon non-protein amino acid, is a major inhibitory neurotransmitter in the mammalian brain [1]. Clinical research showed that it can lower blood pressure, prevent cancers, and reduce cardiovascular diseases [2,3,4]. The GABA content in natural food is far from meeting the physiological needs of the human body. Many functional foods and dietary supplements with GABA as the main raw material are supplied on the market [5,6]. The most common and effective methods to accumulate GABA in edible plants include germinating under stressful conditions such as salt stress. The concomitant growth and biomass of germinating plants are markedly suppressed [7,8,9]
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