Ca2+ involved in GABA signal transduction for phenolics accumulation in germinated hulless barley under NaCl stress.

In this study, in order to investigate the role of Ca²⁺ in GABA signal transduction involved in phenolics accumulation in barley seedlings under NaCl stress, the seedlings were treated with exogenous GABA and its synthesis inhibitor, 3-mercaplopropionic acid (3-MP), as well as Ca²⁺ channel blockers La³⁺, Ca²⁺ chelator EGTA, and Ca²⁺ release channel inhibitor 2-aminoethoxydiphenyl borate (2-APB). The results showed that GABA significantly enhanced phenolics, calcium and calmodulin content. It also induced Ca²⁺ influx in barley root tips cells, and altered the distribution of Ca²⁺, making calcium precipitates more uniform and intensive. While, 3-MP treatment led to opposite changes, which suggested that GABA was essential for calcium content increase. In addition, accumulation of phenolics was inhibited by LaCl₃, EGTA and 2-APB treatments, and this inhibition could be alleviated partly by exogenous GABA. Taken together, Ca²⁺ was involved in GABA signal transduction for phenolics accumulation in barley seedlings under NaCl stress.