The Role of Calcium and Calmodulin in Carrot Somatic Embryogenesis : GROWTH AND DEVELTOPMENT : GENES STRUCTURE AND EXPRESSION

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The role of Ca^<2+> and calmodulin in carrot somatic embryo formation was examined. Embryogenic cell clumps were induced to form embryos in medium containing 0-3 mM Ca^<2+>. Embryo formation was not affected until the concentration of Ca^<2+> was lower than 200 μM and after this threshold was reached the percent of embryo formation decreased with lower Ca^<2+> concentrations. Treatment of developing embryos with either verapamil or nifedipine, Ca^<2+>-channel blockers, or the Ca^<2+> ionophore A23187, inhibited embryo formation. These results suggest that exogenous Ca^<2+> or the maintenance of Ca^<2+> gradients are required for proper embryo development. Analysis of membrane-associated Ca^<2+> and total membrane distribution using the fluorescent dyes chlorotetracycline and N-phenyl-1-napthylamine, respectively, indicated changes in the distribution of membranes during embryogenesis without any significant alterations in the concentration of Ca^<2+> associated with the membranes. In heart- and torpedo-stage embryos, calmodulin-Ca^<2+> complexes were localized in regions containing the developing meristems of both the cotyledon tips and rhizoid regions while total calmodulin protein appeared to be more uniformly distributed. Calmodulin mRNA levels increased slightly when cell clumps were induced to form embryos.
日本植物生理学会の論文