Cyclic ADP-ribose (cADPR) is known to release Ca2+ from plant vacuoles, implying that this NAD+ metabolite may possess a second messenger role in plants. The degree to which the plant cADPR-gated Ca2+ release mechanism resembles cADPR action in animals has been evaluated. cADPR-elicited Ca2+ release from red beet microsomes was inhibited by 1 mM procaine but insensitive to heparin. Furthermore, pre-release of Ca2+ from red beet vesicles by either 5 mM caffeine or micromolar levels of ryanodine precluded further Ca2+ mobilisation by cADPR. Thus, this study argues strongly for conservation between the plant and animal cADPR-elicited Ca2+ release mechanism.
Muir, S. R., & Sanders, D. (1996). Pharmacology of Ca2+ release from red beet microsomes suggests the presence of ryanodine receptor homologs in higher plants. FEBS Letters, 395(1), 39–42. https://doi.org/10.1016/0014-5793(96)01000-9