The physiological effect of GABA priming on pepper (Capsicum annuum L.) during seed germination under salt stress

Abstract

High salinity leads to a reduction in growth, germination, metabolic stability, and production of pepper (Capsicum annuum L.) plants worldwide. GABA priming showed a positive effect on plant growth and development and improved plant stress tolerance. The current study aimed to investigate the effect of exogenous GABA treatments on endogenous GABA shunt pathway in germinating seeds of green bell pepper (Capsicum annuum L.) under salt stress (0, 25, 50, 75, 100 and 200 mM NaCl) through the characterization of seed germination pattern, seedling growth, seed moisture content, GABA shunt metabolite levels (GABA, Alanine, and Glutamate), the level of oxidative damage in terms of the accumulation of reactive oxygen substances and the expression of pepper dehydrin gene (CaDHN3) in response to all salt stress treatments that were examined in this study. Pre-treatment of pepper seeds with GABA improved seed germination by enhancing germination percentage, germination rate, seedling length, seedling fresh and dry weights, seed moisture content, and decreasing mean time to germinate under salt stress. Data showed an increase with positive correlation between internal GABA metabolite, alanine, and glutamate levels and NaCl concentrations in response to all GABA priming treatments. The MDA content increased as NaCl concentration increased under all GABA treatments. However, there was a significant reduction in MDA content in all GABA treatments and hydro-primed pepper seeds when compared to untreated seeds under all NaCl concentrations. The expression of pepper dehydrin gene (CaDHN3) was significantly increased with the increase of NaCl concentrations under all GABA treatments. Priming pepper seeds with exogenous GABA significantly activates GABA shunt and accumulate GABA internally to maintain C: N balance, stabilize internal metabolism, sustain amino acid metabolism, enhance scavenging of reactive oxygen species (ROS) by activating defense mechanisms, and significantly increase the expression of CaDHN3 to prevent lipid peroxidation, maintain metabolic stability and enzymes function and prevent dehydration during seeds germination in response to salt stress.