Structure and Expression of a Gene for the Large Subunit of Ribulose-1,5-bisphosphate Carboxylase/Oxygenase from Pine

The nucleotide sequence of the gene for the large subunit (LSU) of ribulose-l,5-bisphosphate carboxylase/oxygenase (RuBisCO) in pine (Pinus thunbergii) was determined. The pine gene for LSU (rbcL) contained 1,425 bp which encoded 475 amino acids. The nucleotide sequence and the deduced amino acid sequence each showed a very high degree of homology to the corresponding sequences from angiosperms. The rbcL transcript started from about 120 nucleotides upstream from the initiation codon and terminated about 120 nucleotides downstream from the termination codon. The promoter sequence was highly homologous to those of angiosperms. Two inverted repeats were found in the region that corresponded to the 3'-terminus of the transcript. However, the nucleotide sequence in the inverted repeats was very different from such sequences in angiosperms. Since the accumulation of LSU, as well as that of chlorophylls, has been observed in dark-grown pine seedlings, we studied the expression of the pine rbcL under-various conditions. Levels of the rbcL transcript increased even in the dark during the germination of pine seeds. The gene dosage also increased in a light-independent manner. In addition, it appeared that the mature transcript was stored in dry embryos and that transcription occurred within three days of imbibition. The results suggest that rbcL is expressed continuously during the germination of pine seeds.