The use of nuclear-encoded sequences to direct the light-regulated synthesis and transport of a foreign protein into plant chloroplasts.

The light-inducible nuclear gene coding for the small subunit of ribulose-1,5-bisphosphate carboxylase (Rubisco), produces a precursor protein with an amino-terminal transit peptide which is transported into the plastids and cleaved by a specific proteinase. To test whether the promoter and transit peptide-coding sequences of the small subunit gene can be used to direct the light-inducible synthesis and transport of a foreign protein into chloroplasts, a chimeric gene was constructed consisting of the promoter, first exon and intron as well as part of the second exon of the small subunit Rubisco gene fused to the amino-terminal end of the neomycin phosphotransferase II gene (nptII) of Tn5. Tobacco tissue, as well as whole plants, into which this chimaeric gene was introduced, were resistant to kanamycin. The transcription of the chimaeric gene as well as the NPTII activity of the resulting fusion protein were shown to be light inducible. The fusion protein is processed and located within the chloroplasts of the transformed plants.