Melatonin treatment promotes endogenous melatonin accumulation and triggers GABA shunt pathway activity in tomato fruits during cold storage

Higher H2O2 accumulation in tomato fruits during storage at 4 degrees C for 7 days by melatonin treatment at 100 mu M may serve as signaling molecule for promoting endogenous melatonin accumulation by trigerring melatonin biosynthesis TDC, T5H, SNAT, and ASMT genes expression during storage at 4 degrees C for 28 days. Also, higher GABA shunt pathway activity demonstrating by higher GAD, GABA-T and SSADH enzymes activity in tomato fruits treated with melatonin may be responsible for promoting phenylpropanoid pathway activity demonstrating by higher PAL gene expression and enzyme activity giving rise to higher phenols accumulation and higher DPPH scavenging capacity during storage at 4 degrees C for 28 days. Hence, exogenous melatonin treatment may serve as beneficial procedure for response to chilling stress in tomato fruits by signaling H2O2 accumulation responsible for promoting endogenous melatonin accumulation accompanying by stimulating GABA shunt pathway activity.