Increase of calmodulin level in the early phases of radish (Raphanus sativus) seed germination

INCREASE OF CAlMODULIN LEVEL IN EARLY PHASES OF RADISH ( Rophanus sativuvus) SEED GERMINATION. Cocucci,M., Marre,E. c /o , Istitulo di Botonico,v.Castelli 2, 98100 Messinoi Istituto di Scienze Botaniche, v. G .Colombo 60,20133 Milano, Italy The presence of calmodulin in germinating radish seeds has been demonstrated by the fluphenazinen-sephoarose affinity chromatography of extrct from 24h germinated seeds. Radish calmodulin shows characteristics very close to the ones of brain calmodulin: heat stability, electrophoretic mobility on SDS-polyacrylamide gel and kinetic of Co2+ dependent activation of brain phosphodiesterase (PDE). Calmodul in level in radish extracts were assayed by the PDE activation; experiments with labelled radish calmodulin (125I) indicate 0 90% recovery during the extraction. The amount of calmodulin in the embrional axis of 24h germinated seeds is much higher than that in the cotyledons. Calmodulin level in the postmicrosomal supernatant from embrional axis strongly increases during the first 24h of germination. No detectable amounts of calmodulin were found in the heavier fractions.