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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]

• 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]