Accumulation of γ-aminobutyric acid and transcription of glutamate decarboxylase in Brassica juncea (L.) Czern

Mustard leaf (Brassica juncea (L.) Czern.) using as material of a traditional fermented vegetable food (Kimchi) in Korea, is one of the important vegetables. Two cultivars of mustard (red and green) were grown in the experimental farm of Chungnam National University and allowed them to grow until flowering stage. In this study, the variability of γ-aminobutyric acid (GABA) content and mRNA transcript levels of genes involved in GABA biosynthesis were investigated in 2 cultivars (green and red mustard) of Brassica juncea. We observed that the transcript levels of glutamate decarboxylase (GAD) 1, 2, and 4a in roots were the highest, whereas those in seeds were the lowest compared with other organs harvested at flowering stage in green mustard. The transcript levels in green and red mustards displayed similar transcription patterns among a variety of organs, except for those of BjGAD2 and 4a in roots. In red mustard, the GABA content in flower buds was the highest (179.8 mg 100 g FW), whereas roots contained the lowest amount (1.77 mg 100 g FW). In green mustard, the GABA content in young leaves was the highest (97.76 mg 100 g FW), whereas seeds had the lowest (1.23 mg 100 g FW). Green and red mustard contained varying amounts of GABA in different organs. Specially, because green and red mustard leaf has high GABA content compared with other vegetables, it can be used as a good vegetable for healthy.