A cyclic effect of cAMP and calcium signaling contributes to jujube growth and development1

3′,5′-Cyclic adenosine monophosphate (cAMP) is an important metabolite that is specifically enriched in jujube. However, the effect of cAMP on jujube cellular responses has not been comprehensively studied. Here, we established jujube cell suspension cultures and investigated the calcium influx in response to cAMP treatment through protoplast isolation and fluorescence intensity. Firstly, cAMP treatment could promote jujube growth and increase the content of endogenous cAMP. Using transcriptome analysis with transgenic Arabidopsis plants overexpressing adenylate cyclase (ZjAC) as a positive control, we identified 60 calcium-related differential expressed genes (DEGs) that contributed to the calcium signaling and inter- or intra-cellular responses. Pharmacological treatments such as cAMP and the calcium ionophore A23187 could induce ZjAC expression, the accumulation of cAMP and calcium influx in jujube cells, while ethylene glycol tetraacetic acid (EGTA) or bithionol treatment inhibited these changes. Moreover, the calcium channels and transporters in calcium influx, such as the ZjCNGC2 channel and the mitogen activated protein (MAP) kinase pathway, could be activated by cAMP treatment. In summary, our findings demonstrated that cAMP biosynthesis is dependent on calcium influx and the amplifying effect between calcium and cAMP may be involved in intracellular signal induction, which might contribute to the growth and development of jujube.