Visualization of Membrane Calcium and Calmodulin in Embryo Sacs in situ and Isolated from Petunia hybrida L. and Nicotiana tabacum L.

We have used chlorotetracycline (CTC) and fluphenazine (FPZ)as fluorescent probes to visualize the distributional patternsof membrane calcium (mCa²⁺) and the Ca²⁺-receptor protein calmodulin(CaM) in various cell types of unfixed living isolated and unisolatedembryo sacs of Petunia hydrida L. and Nicotiana tabacum L. Ourresults indicate that in the young embryo sacs of Petunia, bothsynergids and the central cell sequester relatively higher amountsof mCa²⁺ and CaM than the egg cell and the antipodals. Much of the mCa²⁺ in the synergids is polarized in its distributionin that the mCa²⁺ is higher towards the micropylar end of thesynergids. Interestingly, in the mature embryo sacs of Petuniaonly one of the two synergids and the egg cell proper manifesta higher level of mCa²⁺. In vivo only one of the synergids inthe young as well as in the mature embryo sacs if Nicotianaconsistently show higher mCa²⁺. In the mature embryo sacs of Petunia the level of CaM is almostuniform in all the cell types except that one of the synergidsand the three antipodal cells show a slightly higher level ofCaM. The possible implications of these findings in the late eventsof vectorial orientation of pollen tube tip, pollen-tube-synergidinteractions and sperm delivery mechanism are discussed.Copyright1993, 1999 Academic Press Membrane-Ca²⁺, calmodulin, living embryo sacs, Petunia, Nicotiana, pollen tube-synergid interaction