Nuclear control of early plastid differentiation

The review summarizes the main results which have been obtained concerning the expression of nuclear genes encoding plastid-destined proteins during the early steps of plastid development. In particular, results showing that nuclear genes for plastid ribosomal proteins are expressed very early after seed imbibition and that their expression precedes the expression of plastid-encoded genes, are presented. Also, results concerning the differential control of the expression of nuclear genes encoding ribosomal proteins in root amyloplasts and leaf chloroplasts are reported. Hypotheses concerning the specific function during early plastid development, of the recently characterized, nucleus-encoded, plastid RNA polymerase, are given.