NUCLEAR CONTROL OF EARLY PLASTID DIFFERENTIATION

The review summarizes the main results which have been obtained concer ning the expression of nuclear genes encoding plastid-destined protein s during the early steps of plastid development. In particular, result s showing that nuclear genes for plastid ribosomal proteins are expres sed very early after seed imbibition and that their expression precede s the expression of plastid-encoded genes, are presented. Also, result s concerning the differential control of the expression of nuclear gen es encoding ribosomal proteins in root amyloplasts and leaf chloroplas ts are reported. Hypotheses concerning the specific function during ea rly plastid development, of the recently characterized, nucleus-encode d, plastid RNA polymerase, are given.