cis-Acting Elements for Light Regulation of Pea Ferredoxin I Gene Expression Are Located within Transcribed Sequences.

An intact pea gene encoding ferredoxin I (Fed-1) and several chimeric constructs containing portions of Fed-1 were introduced into tobacco plants by Agrobacterium-mediated transformation. The intact gene was correctly transcribed and translated to produce a protein that was imported into the chloroplast and processed to its mature size. Fed-1 mRNA accumulation in these plants was strongly light-dependent, as it is in pea leaves. In chimeric constructs, the Fed-1 promoter was active but no light responses were seen, even when as much as 2 kilobases of 5[prime] -flanking sequence were included. We also failed to observe clear light responses with a construct containing 3[prime] -flanking sequences from Fed-1 attached to a [beta]-glucuronidase gene driven by the cauliflower mosaic virus 35S promoter. However, the transcribed portion of Fed-1 conveyed normal light responsiveness when driven by the 35S promoter. The results are discussed in terms of the hypothesis that light determines Fed-1 mRNA abundance by affecting RNA stability rather than by affecting transcription.