Exogenous calcium chloride (CaCl2) promotes γ-aminobutyric acid (GABA) accumulation in fresh-cut pears

Effect of calcium chloride (CaCl2) on gamma-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 CaCl2 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 CaCl2 treatment correspondingly. Meanwhile, the Ca2+ channel blockers lanthanum chloride (LaCl3) 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 CaCl2 seems to be more effective to GABA shunt, while LaCl3 treatment mightily stimulate GABA shunt and polyamine degradation pathway.