PHARMACOLOGY OF CA2-PLANTS( RELEASE FROM RED BEET MICROSOMES SUGGESTSTHE PRESENCE OF RYANODINE RECEPTOR HOMOLOGS IN HIGHER)

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 Ca2from red beet vesicles by either 5 mM caffeine or micromolar levels of ryanodine precluded further Ca2+ mobilisation by cADPR, Thus, this st udy argues strongly for conservation between the plant and animal cADP R-elicited Ca2+ release mechanisms.