Exogenous γ-Aminobutyric Acid Treatment That Contributes to Regulation of Malate Metabolism and Ethylene Synthesis in Apple Fruit during Storage

• DOI: 10.1021/acs.jafc.8b04674
• Publication Date: 2018-12-04T19:55:53Z
• Authors: Shoukun Han; Yuyu Nan; Wei Qu; Yiheng He; Qiuyan Ban; Yanrong Lv; Jingping Rao
• Keywords: 0301 basic medicine; 2. Zero hunger; Malates; Ethylenes; 03 medical and health sciences; Malate Dehydrogenase; Food Preservation; Fruit; Malus; Food Preservatives; Phosphoenolpyruvate Carboxykinase (ATP); gamma-Aminobutyric Acid; Plant Proteins

Organic acid is an important indicator of fruit quality, and malate is the predominant organic acid in apple fruit. However, the regulation of malate metabolism in postharvest fruit is rarely reported. Here, we found that, compared with a control treatment, a 10 mM γ-aminobutyric acid (GABA) treatment remarkably delayed the loss of tiftratable acidity and malate and increased the succinate and oxalate contents in "Cripps Pink" fruit stored in polyethylene bags at room temperature. The higher malate levels in GABA-treated fruit were accompanied by higher activities of cytosolic nicotinamide adenine dinucleotide-dependent malate dehydrogenase (cyNAD-MDH) and phosphoenolpyruvate carboxylase (PEPC) but lower cytosolic NAD phosphate-dependent malic enzyme (cyNADP-ME) and phosphoenolpyruvate carboxykinase (PEPCK) activities than those seen in control fruit. Notably, ethylene production was significantly reduced by GABA treatment, paralleling the downregulation of MdACS, MdACO, and MdERF expression. Meanwhile, GABA treatment also enhanced the activity of the GABA shunt and promoted the accumulation of GABA. This study provides new insights into the regulation of malate metabolism and reports for the first time the possible interplay between GABA and ethylene signaling pathways in apple fruit during postharvest storage.