Isolation and sequence analysis of cDNA clones encoding the precursor of the 10-kDa polypeptide of photosystem II from tobacco

Several cDNA clones encoding the precursor of the 10-kDa protein of photosystem II were isolated from a cDNA library of tobacco mesophyll protoplasts, utilizing the c DNA of the 10-kDa protein from potato (ST-LS1 gene) as a probe. One of the clones, NtPII-10, encodes an amino acid sequence of 136 residues. Sequence comparison with the 10-kDa polypeptides from spinach, Arabidopsis thaliana and potato reveals 64.9%, 59.5% and 73.0% amino acid identity respectively on the transit peptide and 80.8%, 83.8% and, 93.9% on the mature polypeptide, respectively. The transit peptide is 4 and, 2 amino acid residues shorter in tobacco than in spinach and A. thaliana and, respectively, potato. A second tobacco cDNA clone, NtPII-9, contains the same coding sequence and a 3'-untranslated region 41 nucleotides shorter, due to alternative polyadenylation sites. We show that in tobacco the 10-kDa protein is encoded by a single-copy, light-inducible gene (psbr).