Calcium-induced calcium release mediated by a voltage-activated cation channel in vacuolar vesicles from red beet

Little is known about the mechanisms underlying calcium-induced Ca2+ releas e (CICR) in plants. The slow-activating vacuolar (SV) channel is both perme able to, and activated by Ca2+, and is therefore a prime candidate for a ro le in CICR, Cytosol-side-out vacuolar membrane vesicles loaded with Ca-45(2 +) showed voltage- and Ca2+-dependent Ca2+ release, which was sensitive to the SV channel modulators DIDS, protein phosphatase 2B and calmodulin, Sign ificantly, voltage-dependent Ca2+ release strongly depended on cytoplasmic Ca2+ concentrations. The results support the notion that CICR occurs in pla nt cells and that the process can be catalysed by the SV channel on the vac uolar membrane. (C) 1999 Federation of European Biochemical Societies.