Ca2+ acts as a second messenger which controls a wide variety of cellular functions. Ca2+ homeostasis is accomplished by a complex of mechanisms including pumps, ion channels and calcium buffers within storage compartments. Calreticulin is the low-affinity, high-capacity Ca2+-binding protein of most eucaryotic cells. The distribution of calreticulin was studied in isolated protoplasts and during different stages of somatic embryogenesis in carrot (Daucus carota L. cv. St Valery Lunga Rossa) suspension culture. Immunofluorescence staining of protoplasts showed the presence of calreticulin in the cytoplasm. No calreticulin was observed within vacuoles. During somatic embryogenesis calreticulin was distributed mainly in the protoderm of developing embryos in different stages.
In this paper we are presenting a critical review of works demonstrating that at the early stages of apoptosis eukaryotic DNA is cleaved to large fragments the length of which is several tens of thousands of nucleotide pairs. Evidence is presented that this fragmentation proceeds in a specific fashion and that the character of the fragmentation reflects the general principle of eukaryotic genome organization into structural-functional domains.