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

Abstract

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 GAD expression in cotyledon and radicle, while upregulated that in shoot; it also upregulated DAO expression in each organ. CaCl2 upregulated GAD expression in cotyledon, while downregulated that in radicle. However, it upregulated DAO 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 Ca(2+), respectively. However, they upregulated GAD and DAO expression in varying degrees. These results indicate that ABA and Ca(2+) participate in GABA biosynthesis in fava bean during germination under hypoxia-NaCl stress.

Peer Review #2 of "Identification of two CiGADs from Caragana intermedia and their transcriptional responses to abiotic stresses and exogenous abscisic acid (v0.2)"

“…In our previous study, we found that exogenous GABA induced the expression of the ABA-biosynthetic gene ABA2 in Caragana under salt stress (Shi et al, 2010). Exogenous ABA has also been shown to enhance GAD activity and increase the GABA content in fava bean (Yang et al, 2016), and to induce the expression of ZmGAD1, which harbors ABA-related cis-elements in its promoter (Zhuang et al, 2010). In the present study, we found that exogenous ABA increased the transcript levels of CiGAD1 and CiGAD2 at an early stage (3 h) of the salt treatment (Fig.7A, B); while after 24 h of salt treatment, the transcript levels of both genes were reduced in the roots of ABA-treated plants, but strongly increased in the leaves of plants treated with 0.5 μM ABA (Fig.…”

Effects of Salicylic Acid on Gaba Metabolism in Pepper Plants under Stress Conditions

“…GAD, the key enzyme in GABA-shunt, catalyzes the conversion of glutamate to GABA. The earlier studies indicate the increase in GAD activity under NaCl stress and also supplemental of CaCl 2 [24,25].…”

Recent advances in γ‐aminobutyric acid (GABA) properties in pulses: an overview

“…found that to obtain 80% of GAD activity in rice bran, a pH range from 5 to 9 and a temperature between 30 °C and 50 °C are essential. In contrast, EDTA chelates metal ions such as Ca 2+ and thus, through GAD and GAO inactivation, can lead to a reduction in GABA generation . In support of this hypothesis, Yang et al .…”

“…There are other factors that can enhance GABA production in pulses such as the plant hormone abscisic acid (ABA) (a stress hormone) that was found to raise GABA accumulation in faba beans under hypoxia–NaCl stress . Other researchers have reported similar effects of ABA in common bean ( Phaseolus vulgaris ) demonstrating that ABA treatment (concentrations of 1 and 10 μM) resulted in the acceleration of GABA metabolism through lowering the negative effect of high NaCl concentration .…”