EVIDENCE THAT THE PLASTID SIGNAL AND LIGHT OPERATE VIA THE SAME CIS-ACTING ELEMENTS IN THE PROMOTERS OF NUCLEAR GENES FOR PLASTID PROTEINS

Nuclear-encoded genes for proteins of the photosynthetic maschinery re present a particular subset of genes. Their expression is cooperativel y stimulated by discrete factors including the developmental stage of plastids and light. We have analyzed in transgenic tobacco the plastid - and light-dependent expression of a series of 5' promoter deletions of various nuclear genes from spinach, of fusions of defined promoter segments with the 90-bp 35S RNA CaMV minimal promoter, as well as with mutations in sequences with homologies to characterized cis-elements, to address the question of whether the plastid signal and light opera te via the same or different cis-acting elements. In none of the 160 d ifferent transgenic lines (representing 32 promoter constructs from se ven genes) analyzed, could significant differences be identified in th e responses to the two regulatory pathways. The data are compatible wi th the idea that both signals control the expression of nuclear genes for plastid proteins via the same cis-acting elements.