Effects of ABA and CaCl₂ on GABA accumulation in fava bean germinating under hypoxia-NaCl stress

<div><p>Effects of exogenous abscisic acid (ABA) and CaCl₂ on γ-aminobutyric acid (GABA) accumulation of germinated fava bean under hypoxia-NaCl stress were investigated. Exogenous ABA resulted in the enhancement of glutamate decarboxylase (GAD) and diamine oxidase (DAO) activity as well as GABA content in cotyledon and shoot. CaCl₂ increased both enzyme activities in shoot and GABA content in cotyledon and shoot. ABA downregulated <i>GAD</i> expression in cotyledon and radicle, while upregulated that in shoot; it also upregulated <i>DAO</i> expression in each organ. CaCl₂ upregulated <i>GAD</i> expression in cotyledon, while downregulated that in radicle. However, it upregulated <i>DAO</i> expression in shoot, downregulated that in radicle. ABA inhibitor fluridon and ethylenediaminetetraacetic acid inhibited GAD and DAO activities significantly so that inhibited GABA accumulation through reducing ABA biosynthesis and chelating Ca²⁺, respectively. However, they upregulated <i>GAD</i> and <i>DAO</i> expression in varying degrees. These results indicate that ABA and Ca²⁺ participate in GABA biosynthesis in fava bean during germination under hypoxia-NaCl stress.</p></div

Mechanism of Calcium Lactate Facilitating Phytic Acid Degradation in Soybean during Germination

Calcium lactate facilitates the growth and phytic acid degradation of soybean sprouts, but the mechanism is unclear. In this study, calcium lactate (Ca) and calcium lactate with lanthanum chloride (Ca+La) were used to treat soybean sprouts to reveal the relevant mechanism. Results showed that the phytic acid content decreased and the availability of phosphorus increased under Ca treatment. This must be due to the enhancement of enzyme activity related to phytic acid degradation. In addition, the energy metabolism was accelerated by Ca treatment. The energy status and energy metabolism-associated enzyme activity also increased. However, the transmembrane transport of calcium was inhibited by La³⁺ and concentrated in intercellular space or between the cell wall and cell membrane; thus, Ca+La treatment showed reverse results compared with those of Ca treatment. Interestingly, gene expression did not vary in accordance with their enzyme activity. These results demonstrated that calcium lactate increased the rate of phytic acid degradation by enhancing growth, phosphorus metabolism, and energy metabolism