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Increase in calmodulin level in the early phases of radish seed ( Raphanus sativus ) germination
Author(s) -
COCUCCI MAURIZIO
Publication year - 1984
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/1365-3040.ep11614660
Subject(s) - raphanus , germination , calmodulin , abscisic acid , embryo , biology , botany , horticulture , chemistry , biochemistry , enzyme , microbiology and biotechnology , gene
Calmodulin (Cam), the heat‐stable, ubiquitous, Ca 2+ ‐dependent regulator protein, has been purified to apparent homogeneity from germinating radish seeds ( Raphanus sativus ). The characteristics of radish Cam‐molecular weight, absorption spectrum, Ca 2+ ‐dependent activation of brain phosphodiesterase (PDE)‐are very similar to those described for Cam from other plant materials. Radish Cam, like other plant Cam, shows some differences to Cam of calf brain. The total amount of Cam in radish embryos at 24 h of germination is ca. 37 μg g −1 fresh weight. Approximately 95% of the total amount of Cam is present in the soluble fraction (supernatant at 100,000 g ). The level in the embryo axis strongly increases in the first 24 h of germination (+540%); this increase is strongly reduced when the germination is inhibited by abscisic acid (ABA). In the presence of Ca 2+ , no ‘free’ Cam (i.e. not bound to other structures) is present in the soluble fraction, suggesting that, during early germination, Cam level is a limiting factor for the activities of Ca 2+ ‐Cam‐dependent systems. These studies suggest that Cam plays an important role in the early phases of seed germination. An inhibitor of the Ca 2+ ‐Cam‐dependent phosphodiesterase is present in the soluble fraction from radish embryos; this substance decreases during germination. A possible role of this inhibitor during the early germination phases is hypothesized.