MOLECULAR-CLONING OF THE ARABIDOPSIS-THALIANA SEDOHEPTULOSE-1,7-BIPHOSPHATASE GENE AND EXPRESSION STUDIES IN WHEAT AND ARABIDOPSIS-THALIANA

We report here the isolation and nucleotide sequence of genomic clones encoding the chloroplast enzyme sedoheptulose-1,7-bisphosphatase (SBP ase) from Arabidopsis thaliana. The coding region of this gene contain s eight exons (72-76 bp) and seven introns (75-91 bp) and encodes a po lypeptide of 393 amino acids. Unusually, the 5' non-coding region cont ains two additional AUG codons upstream of the translation initiation codon. A comparison of the deduced Arabidopsis and wheat SBPase polype ptide sequences reveals 78.6%, identity. Expression studies showed tha t the level of SBPase mRNA in Arabidopsis and wheat is regulated in a light-dependent manner and is also influenced by the developmental sta ge of the leaf. Although the Arabidopsis SBPase gene is present in a s ingle copy, two hybridizing transcripts were detected in some tissues, suggesting the presence of alternate transcription start sites in the upstream region.