Ca(2+) 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 Ca(2+) 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 Ca(2+) channel blockers La(3+), Ca(2+) chelator EGTA, and Ca(2+) release channel inhibitor 2-aminoethoxydiphenyl borate (2-APB). The results showed that GABA significantly enhanced phenolics, calcium and calmodulin content. It also induced Ca(2+) influx in barley root tips cells, and altered the distribution of Ca(2+), 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 LaCl(3), EGTA and 2-APB treatments, and this inhibition could be alleviated partly by exogenous GABA. Taken together, Ca(2+) was involved in GABA signal transduction for phenolics accumulation in barley seedlings under NaCl stress.