A number of different nuclear genes for the small subunit of RuBPCase are transcribed in petunia.

The sequences in the petunia genome which encode the small subunit polypeptides of the chloroplast enzyme ribulose-1,5-bisphosphate carboxylase have been characterized. Sequence analysis of four cDNA clones indicate that there are several distinct genes transcribed in leaf tissue. There is 8-9% nucleotide divergence between the transcripts however these changes do not alter the encoded amino acid sequence. Examination of nuclear DNA by Southern hybridization and analysis of cloned small subunit genes confirm that there are a number of different genes which encode this single protein.