Enhancement of DNA repair in gamma-irradiated spheroplasts and nuclei of dark-grown Euglena cells by the supernatant of light-grown Euglena cells or their chloroplasts

Abstract

Spheroplasts and nuclei of dark-grown Euglena cells (cells devoid of chloroplasts), which rejoin only some of the single strand breaks in DNA produced by gamma radiation, can rejoin all the strand breaks with post-irradiation incubation in the presence of supernatant derived either from light-grown cells or their chloroplasts but not from dark-grown cells. DNA repair efficiency of the spheroplasts correlates with an increase in the level of chloroplast supernatant proteins in the incubation system. The magnitude and the efficiency of DNA repair in the nuclei of dark-grown cells, thus increased, reach those in the nuclei of light-grown cells (cells with chloroplasts). Addition of the chloroplast supernatant to the incubation system of the nuclei from light-grown cells does not affect the repair of DNA. The results indicate that some factor(s) elaborated by chloroplasts may contribute towards the efficiency of nuclear DNA repair in Euglena cells.