Study On Γ-Aminobutyric Acid Accumulation And Regulation Techniques In Germinated Fava Benas(Vida Faba L.)

The method of hypoxia combined with NaCl stress was used for treating fava bean. The culture conditions and culture solution composition for GABA accumulation in germinated fava bean was optimized. The changes of DAO activity, GABA and precursor content in different parts of germinated fava bean were studied after adding AG(DAO inhibitor). The contribution rate of Pas(polyamines) degradation on GABA accumulation was analyzed. By adding exogenous Ca2+, the effect of Ca2+on GABA accumulation in germinating fava bean was studied. In the optimal culture conditions and medium, the changes of main physiological and biochemical index, GABA content, enzyme activity and precursor content during germination were determined. The main results were the following:Under the condition of hypoxia combined with NaCl stress, the effects of culture time, pH and stress time on GABA accumulation in germinating fava bean was significante. The optimum culture conditions of GABA accumulation in germinated fava bean were culture time of1.5d, pH of3.5and stress time of4d. The effects of MSG, CaCl2and VB6on GAD and GABA of germinating fava bean all reached significant level(.P<0.05). The optimum compositions of culture solution for GABA accumulation were MSG of1.1mg/mL, CaCl2of6.1mmol/L and VB6of72μmol/L. Under these conditions, the content of GABA was1.98±0.09mg/g DW, which was1.83times of the control.Under the condition of hypoxia combined with NaCl stress, the sprout length, DAO activity and GABA content of fava bean were significantly inhibited after treating with AG. When the concentration of AG was5mmol/L, the growth and development of fava bean, DAO activity and GABA content were lower than the control with the increase of treatment time. Under the condition of hypoxia combined with NaCl stress, GABA accumulation in cotyledon and embryo of fava bean that contributed by polyaxine oxidative degradation pathway was25.0%and29.3%, respectively.Under the condition of hypoxia combined with NaCl stress, CaCl2treatment significantly improved GAD and DAO activity in cotyledon of fava bean, so GABA content of cotyledon increased24.4%compared with the control, while GABA content of embryo did not change significantly. After adding EGTA, DAO activity in cotyledon and embryo of fava bean were inhibited significantly; GABA content was also decreased significantly.Under the condition of hypoxia combined with NaCl stress, the growth of fava bean was slowed, and the respiration of fava bean was enhanced after adding MSG, CaCl2and VB6. During germination, starch content was reduced; reducing sugar, soluble protein and free amino acid content were accumulated; GAD and DAO activity were increased; GABA content was also increased. Correlation analysis showed that there was a significant positive correlation between GABA content and GAD activity, Put and Spd content.