Spinacia oleracea chloroplast DNA sequence homology with ARS and ARC elements within the inverted repeat, upstream of the rDNA operon

摘要

The sequence of a chloroplast Bgl II-Pvu II DNA fragment from spinach bearing 691 bp upstream of the 16S rRNA gene has been described (1). The first aminoacids of an ORF were located on the non coding strand for the ribosomal genes. The sequence of the Bam HI-Bgl II DNA fragment of pSoc BIO (1), containing the remainder of this ORF 1s presented here. It ends at position - 766 relative to the nucleotide + 1 of the 16S rRNA gene. Furthermore, an AT rich sequence located between positions 440 and 583 and flanked by GC blocks 1s composed of three direct repeats of 10 bases showing strong homology with yeast ARS consensus sequence (2, boxed sequences). In addition, a sequence sharing homology with the ARC I element of C. reinhardii (3) overlaps the first putative ARS (broken line box). The ARC II element of C. reinhardii (3) 1s conserved between positions 803 and 814 (broken line box). The localization of these putative elements upstream of the 16S rDNA operon correlates with the origins of replication of chloroplast DNA of some algae (Chlamydomonas, Euglena, Chlorella).