Polyamine Degradation Pathway Regulating Growth and GABA Accumulation in Germinating Fava Bean under Hypoxia-NaCl Stress

Abstract

In plants, γ -aminobutyric acid (GABA) is synthesized by polyami ne degradation pathway besides GABA shunt. Aminoguanidine (AG) is a specific inhibitor of the key enzyme (diamine oxidase, DAO) for GABA formation in polyamine degradation pathway. In this study, AG was applied to study the function s of polyamine degradation pathway on growth and GABA accumulation in germinating fava bean under hypoxia-NaCl stress. The results showed that 5.0 mmol L -1 of AG inhibited DAO activity maximally but not entirely, and inhibited the growth of sprouts simul taneously. Hence, blocking polyamine degradation pathway significantly affected the grow th of germinating fava bean. Polyamine degradation pathway provided 26.9 and 29. 3% of GABA in cotyledon and embryo, respectively, because DAO activity was not inhibited entirely. Polyamine, especially putrescine (Put), accumulated after poly amine degradation pathway was blocked, indicating that Put was the main substrate of GABA in polyamine degradation pathway. Keywords : Aminoguanidine, Diamine oxidase, Putrescine, γ -aminobutyric acid.