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The γ-aminobutyric acid (GABA) is a widely distributed neurotransmitter in living organisms, known for its inhibitory role in animals. GABA exerts calming effects on the mind, lowers blood pressure in animals, and enhances stress resistance during the growth and development of plants. Enhancing GABA content in plants has become a focal point of current research. In plants, GABA is synthesized through two metabolic pathways, the GABA shunt and the polyamine degradation pathway, with the GABA shunt being the primary route. Extensive studies have investigated the regulatory mechanisms governing GABA synthesis. At the genetic level, GABA production and degradation can be modulated by gene overexpression, signaling molecule-induced expression, transcription factor regulation, and RNA interference. Additionally, at the level of transporter proteins, increased activity of GABA transporters and proline transporters enhances the transport of glutamate and GABA. The activity of glutamate decarboxylase, a key enzyme in GABA synthesis, along with various external factors, also influences GABA synthesis. This paper summarizes the biological functions, metabolic pathways, and regulatory mechanisms of GABA, providing a theoretical foundation for further research on GABA in plants. [ABSTRACT FROM AUTHOR]

In order to explore the influence of sugar treatment on the enrichment of γ-aminobutyric acid (GABA) in peanut sprouts, this paper selected the optimal application concentration of different types of exogenous sugars (mannose, sucrose and glucose). The effects of GABA on the germination of peanut seeds and the related substances of GABA anabolic metabolism were investigated and the possible mechanism of action was studied. The results showed that mannose, sucrose and glucose treatment could significantly (P

In order to explore the influence of sugar treatment on the enrichment of γ-aminobutyric acid (GABA) in peanut sprouts, this paper selected the optimal application concentration of different types of exogenous sugars (mannose, sucrose and glucose). The effects of GABA on the germination of peanut seeds and the related substances of GABA anabolic metabolism were investigated and the possible mechanism of action was studied. The results showed that mannose, sucrose and glucose treatment could significantly (P<0.05) increase the content of GABA in peanut sprouts, and the activity of glutamate decarboxylase (GAD), diamine oxidase (DAO), polyamine oxidase (PAO) and the contents of glutamic acid, putrescine, spermidine and spermidine were significantly changed in oxidase (P<0.05). At the same time, according to the test results, different exogenous sugar treatments could increase the contents of ascorbic acid, protein and resveratrol in peanut sprouts to different degrees. GABA in peanut sprouts can be enriched by exogenous sugar treatment, and its influence mechanism may be GABA branch and polyamine degradation pathway. [ABSTRACT FROM AUTHOR]

The γ-aminobutyric acid (GABA) is a widely distributed neurotransmitter in living organisms, known for its inhibitory role in animals. GABA exerts calming effects on the mind, lowers blood pressure in animals, and enhances stress resistance during the growth and development of plants. Enhancing GABA content in plants has become a focal point of current research. In plants, GABA is synthesized through two metabolic pathways, the GABA shunt and the polyamine degradation pathway, with the GABA shunt being the primary route. Extensive studies have investigated the regulatory mechanisms governing GABA synthesis. At the genetic level, GABA production and degradation can be modulated by gene overexpression, signaling molecule-induced expression, transcription factor regulation, and RNA interference. Additionally, at the level of transporter proteins, increased activity of GABA transporters and proline transporters enhances the transport of glutamate and GABA. The activity of glutamate decarboxylase, a key enzyme in GABA synthesis, along with various external factors, also influences GABA synthesis. This paper summarizes the biological functions, metabolic pathways, and regulatory mechanisms of GABA, providing a theoretical foundation for further research on GABA in plants.

Aromatic rice is considered an important commodity in the global market because of its strong aroma and eating and cooking quality. Asian countries, such as India and Pakistan, are the leading traders of Basmati rice, whereas Thailand is the major supplier of Jasmine rice in the international market. The strong aroma of rice is associated with more than 300 volatile compounds, among which 2-acetyl-1-pyrroline (2-AP) is the principal component. 2-AP is a phenotypic expression of spontaneous mutations in the recessive gene OsBadh2 or Badh2. The present review focuses on the origin, evolution and diversity of genetic resources of aromatic rice available worldwide. A brief discussion is presented on the genes responsible for quality traits along with details of their molecular genetics. This compilation and discussion will be useful for future breeding programs and the biofortification of quality traits of aromatic rice to ensure food security and nutritional need.

Aromatic rice is considered an important commodity in the global market because of its strong aroma and eating and cooking quality. Asian countries, such as India and Pakistan, are the leading traders of Basmati rice, whereas Thailand is the major supplier of Jasmine rice in the international market. The strong aroma of rice is associated with more than 300 volatile compounds, among which 2-acetyl-1-pyrroline (2-AP) is the principal component. 2-AP is a phenotypic expression of spontaneous mutations in the recessive gene OsBadh2 or Badh2. The present review focuses on the origin, evolution and diversity of genetic resources of aromatic rice available worldwide. A brief discussion is presented on the genes responsible for quality traits along with details of their molecular genetics. This compilation and discussion will be useful for future breeding programs and the biofortification of quality traits of aromatic rice to ensure food security and nutritional need. [ABSTRACT FROM AUTHOR]

The effect of exogenous γ-aminobutyric acid (GABA) and GABA synthesis inhibitor 3-mercaptopropionic acid (3-MP) on GABA metabolism and quality in fresh-cut pumpkin was investigated, and the possible mechanism was studied. The results indicated that exogenous GABA induced the accumulation of endogenous GABA and promoted the conversion of glutamic acid to GABA in fresh-cut pumpkin through the catalytic conversion of highly active glutamate decarboxylase (GAD). The 3-MP-treated pumpkin retained lower GABA content than the control, and the activities of GAD and GABA transaminase (GABA-T) were inhibited. The GABA-treated pumpkins possessed relatively lower polyamines (putrescine, spermine and spermidine) contents in comparison with the control during storage. 3-MP treatment restrained the activities of polyamine oxidase (PAO), diamine oxidase (DAO) and amino aldehyde decarboxylase (AMADH). These results demonstrated that GABA treatment could activate the polyamine degradation pathway and promote GABA enrichment in pumpkin. Meanwhile, no significant differences in maximum colony count, color, β-carotene content and soluble solids content were observed among treatments during storage, which suggested that exogenous GABA had little effect on the quality of fresh-cut pumpkin.

Effect of fresh-cut procedure on the accumulation of GABA in carrots via γ-aminobutyric acid (GABA) shunt and polyamines degradation pathway was investigated. Results showed that fresh-cut processing enhanced glutamate decarboxylase (GAD) activity and expression levels of DcGAD1 and DcGAD2, while reduced GABA transaminase (GABA-T) activity and DcGABA-T1 expression level, which induced the more glutamate (Glu) conversion to GABA. Polyamines (PAs) in shredded carrots were significantly lower than the whole, due to the elevated activities of diamine oxidase (DAO), polyamine oxidase (PAO) and aminoaldehyde dehydrogenase (AMADH) and DcPAO expression level, which indicated that the polyamines degradation pathway was activated and more PAs were converted to GABA. These results suggested that fresh-cut procedure can induce the accumulation of GABA through activating GABA shunt and polyamines degradation pathway. Besides, fresh-cut processing treatment did not have much adverse effect on the organoleptic quality of carrots. [ABSTRACT FROM AUTHOR]

In this study, heat and relative humidity (HRH) treatment was applied in highland barley for γ-aminobutyric acid (GABA) accumulation. Tibetan highland barley cultivars (25) were selected for comparison and analysis. HRH treatment could accumulate GABA in several hours with low moisture content and high temperature, and the grains were treated for 2.5 h at 65 °C in this study. The GABA content of processed grains under HRH optimal condition ranged from 26.91 to 76.28 mg·100 g−1, which was significantly higher than the initial content (12.78–43.00 mg·100 g−1). The highest GABA accumulation capacity was observed in two-row yellow cultivars (YT1), increasing from 36.52 to 76.28 mg·100 g−1. Correlation analysis showed that the accumulation of GABA after HRH treatment was positively and significantly (p < 0.05) correlated with the contents of protein (0.52), total free amino acids (0.68), threonine (0.53), serine (0.51), glutamate (0.69), glycine (0.49), alanine (0.46), cysteine (0.57), tyrosine (0.50), lysine (0.53), proline (0.40), and glutamate decarboxylase (GAD) activity (0.62), which were closely related to GABA-shunt pathway. The polyamines contents, diamine oxidase (DAO) and polyamine oxidase (PAO) activities, as the substrates and critical enzymes of polyamine degradation pathway, showed no significant correlation with GABA accumulation. The results suggested that the main pathway of GABA accumulation in highland barley under HRH treatment was GABA-shunt pathway.

Highlights • CaCl 2 treatment stimulated a rapid accumulation of GABA in shredded carrots. • A dramatic increase in GABA content was observed in AsA-treated shredded carrots. • GABA accumulated through activating GABA shunt and polyamines degradation pathway. Abstract CaCl 2 or AsA treatment was applied to shredded carrots to explore their influences on GABA content and its metabolic pathway. The metabolites, enzyme activity and gene expression associated with GABA shunt pathway and polyamine degradation were measured. Results demonstrated that treatment with exogenous CaCl 2 or AsA alone not only significantly promoted the activities of glutamate decarboxylase (GAD), GABA transaminase (GABA-T), diamine oxidase (DAO), polyamine oxidase (PAO) and aminoaldehyde dehydrogenase (AMADH), but up-regulated the expressions of DcGAD 1, DcGAD 2, DcGABA-T 1 and DcPAO. Meanwhile, glutamate (Glu) content, a substrate for GABA shunt, was significantly reduced in both two exogenous treatments. In addition, lower putrescine (Put) and spermine (Spm) contents were observed in AsA treatment only. Taken together, our results suggested that both CaCl 2 and AsA treatments could activate GABA shunt pathway and polyamine degradation. CaCl 2 seemed to be more effective to GABA shunt regulation, while AsA to polyamine degradation. [ABSTRACT FROM AUTHOR]

The γ-aminobutyric acid (GABA) is a non-protein amino acid with some functional properties for human health. Its content is usually lower in plant seeds. Hypoxia or salt (NaCl) stress is an effective way for accumulating GABA during seed germination. However, NaCl stress on GABA accumulation under hypoxia is currently infrequent. The effect of NaCl on GABA accumulation in germinating faba bean (Vicia faba L.) under hypoxia was therefore investigated in this study. Faba bean seeds were steeped in citric acid buffer (pH 3.5) containing NaCl with a final O2 concentration of 5.5 mg L-1 and germinated for 5 d. Results showed that 60 mmol L-1 NaCl was the optimum concentration for GABA accumulation in germinating faba beans under hypoxia. Germination for 5 d under hypoxia-NaCl stress was less beneficial for GABA accumulation than only hypoxia (control). Polyamine degradation pathway played a more important role for accumulating GABA in germinating faba bean as an adaptive response to NaCl stress. Removing NaCl significantly increased GABA content, while it decreased glutamate decarboxylase (GAD) activity. Simultaneously, polyamine was accumulated, which might be related to the enhancement of physiological activity after recovery. When treated with aminoguanidine (AG) for 3 d, GABA content decreased by 29.82%. These results indicated that the tolerance ability of GABA shunt to NaCl stress was weaker than that of polyamine degradation pathway. The NaCl treatment for 3 d under hypoxia could raise the contribution ratio of polyamine degradation pathway for GABA accumulation. The contribution ratio of polyamine degradation pathway for GABA formation was 29.82% when treated for at least 3 d. [ABSTRACT FROM AUTHOR]

In this study, heat and relative humidity (HRH) treatment was applied in highland barley for γ-aminobutyric acid (GABA) accumulation. Tibetan highland barley cultivars (25) were selected for comparison and analysis. HRH treatment could accumulate GABA in several hours with low moisture content and high temperature, and the grains were treated for 2.5 h at 65 °C in this study. The GABA content of processed grains under HRH optimal condition ranged from 26.91 to 76.28 mg·100 g−1, which was significantly higher than the initial content (12.78–43.00 mg·100 g−1). The highest GABA accumulation capacity was observed in two-row yellow cultivars (YT1), increasing from 36.52 to 76.28 mg·100 g−1. Correlation analysis showed that the accumulation of GABA after HRH treatment was positively and significantly (p < 0.05) correlated with the contents of protein (0.52), total free amino acids (0.68), threonine (0.53), serine (0.51), glutamate (0.69), glycine (0.49), alanine (0.46), cysteine (0.57), tyrosine (0.50), lysine (0.53), proline (0.40), and glutamate decarboxylase (GAD) activity (0.62), which were closely related to GABA-shunt pathway. The polyamines contents, diamine oxidase (DAO) and polyamine oxidase (PAO) activities, as the substrates and critical enzymes of polyamine degradation pathway, showed no significant correlation with GABA accumulation. The results suggested that the main pathway of GABA accumulation in highland barley under HRH treatment was GABA-shunt pathway. [ABSTRACT FROM AUTHOR]

• CaCl 2 treatment stimulated a rapid accumulation of GABA in fresh-cut pears. • LaCl 3 reduced GABA by inhibition of GABA shunt and polyamine degradation pathway. • CaCl 2 increased GABA content via GABA shunt rather than polyamine degradation. Effect of calcium chloride (CaCl 2) on γ-aminobutyric acid (GABA) accumulation pathways in fresh-cut pears was investigated. The metabolites, enzyme activity and gene expression associated with GABA shunt and polyamine degradation were measured. Results demonstrated that CaCl 2 treatment promoted GABA accumulation and reduced the glutamate (Glu) content in fresh-cut pears. Ca2+ fluorescence in pear cell, glutamate decarboxylase (GAD) activity and its gene expression increased significantly under CaCl 2 treatment correspondingly. Meanwhile, the Ca2+ channel blockers lanthanum chloride (LaCl 3) treatment not only significantly inhibited the activities of GAD, GABA transaminase (GABA-T), diamine oxidase (DAO), polyamine oxidase (PAO) and aminoaldehyde dehydrogenase (AMADH), but also down-regulated the transcripts of PbGAD , PbGABA-T , PbPAO1 and PbPAO2. Taken together, it can be concluded that CaCl 2 seems to be more effective to GABA shunt, while LaCl 3 treatment mightily stimulate GABA shunt and polyamine degradation pathway. [ABSTRACT FROM AUTHOR]