VISUALIZATION OF MEMBRANE CALCIUM AND CALMODULIN IN EMBRYO SACS INSITU 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 patterns of membrane calcium (mCa2+) and the Ca2+-receptor protein calmodulin (CaM) in various cell types of unfixed living isolated and unisolated embryo sacs of Petunia hybrida L. and Nicotiana tabacum L. Our results indicate that in the young isolated embryo sacs of Petunia, both the synergids and the central cell sequester relatively higher amounts of mCa2+and CaM than the egg cell and the antipodals. Much of the mCa2+in the synergids is polarized in its distribution in that the mCa2+is higher towards the micropylar end of the synergids. Interestingly, in the mature embryo sacs of Petunia only one of the two synergids and the egg cell proper manifest a higher level of mCa2+In vivo only one of the synergids in the young as well as in the mature embryo sacs of Nicotiana consistently show higher mCa2+In the mature embryo sacs of Petunia the level of CaM is almost uniform in all the cell types except that one of the synergids and the three antipodal cells show a slightly higher level of CaM. The possible implications of these findings in the late events of vectorial orientation of pollen tube tip, pollen- tube-synergid interactions and sperm delivery mechanism are discussed. © 1993 Annals of Botany Company.