ANALYSIS OF THE CHROMOSOMAL DNA FRAGMENT ISOLATED FROM A HYBRID AUTONOMOUS PLASMID OF CHLAMYDOMONAS-REINHARDTII

The ability of a previously cloned fragment of nuclear DNA of Chlamydo monas reinhardtii (a 2.4-kb, BamH I-EcoR I fragment) to function as th e origin of replication of plasmid pARG7.8.2.4, carrying the homologou s arg7 marker gene of prototrophy for arginine in cells of C, reinhard tii transformants, was studied, As shown by Southern blotting, plasmid pARG7.8.2.4 integrates at several sites of chromosomal DNA of chlamyd omonas without autonomous maintenance in cells. Results obtained using Southern blotting and plasmid rescue techniques demonstrated that pla smid pARG7.8, containing only the arg7 gene, is able both to integrate into the chromosome and to be maintained in some cases, in the autono mous state in Arg(+) transformants of alga. Analysis of the nucleotide sequence of the DNA fragment under study revealed several types of GC -enriched repeats that manifested homology with the nucleotide sequenc e of the arg7 gene in introns 10 and 12.