Apicobasal gradient of chloroplast DNA synthesis and distribution in Acetabularia

Autoradiographic and biochemical experiments have revealed the presence, in vegetative cells of Acetabularia, of an apicobasal gradient of penetration and incorporation of labelled DNA precursors into the chloroplasts. Staining of chloroplasts with the DNA-specific fluorochrome DAPI has shown that the number of chloroplasts without DNA increases from the apex towards the base of the cell. All together, our findings support the existence of an apicobasal gradient of chloroplast DNA synthesis and distribution in Acetabularia.