S1F BINDING-SITE IS RELATED TO BUT DIFFERENT FROM THE LIGHT-RESPONSIVE GT-1 BINDING-SITE AND DIFFERENTIALLY REPRESSES THE SPINACH RPS1 PROMOTER IN TRANSGENIC TOBACCO

Nuclear genes encoding plastid ribosomal proteins are more highly expr essed in leaves than in roots. This leaf-specific induction seems to b e light-independent. We have previously characterized a spinach nuclea r factor S1F binding to a cis-element within the rps1 promoter, which negatively regulates both the rps1 and the cauliflower mosaic virus 35 S promoters in transient expression assays. Here, we show that the S1F binding site is related to but different from the light-responsive Bo x II of the pea rbcS-3A promoter, which is recognized by the nuclear f actor GT-1. Transgenic plant analyses showed that the S1F site tissue- specifically represses the rps1 promoter in roots as well as in etiola ted seedlings. We suggest that the GT-1-related S1F binding site is re sponsible, at least in part, for the transcriptional repression of rps 1 in nonphotosynthetic tissues such as roots.