Stutz, Erhard

1984, Schlunegger, Bibiane, Stutz, Erhard

We sequenced a Bg1II-HindIII DNA fragment of the Euglena gracilis chloroplast genome which most likely carries the single origin of DNA replication according to recent electronmicroscopic mapping studies (Koller and Delius 1982a; Ravel-Chapuis et al. 1982). This DNA fragment contains a polymorphic region (Schlunegger et al. 1983) which is composed, as will be shown, of multiple tandem repeats (54 bp, 87% A+T). Furthermore we located on this DNA fragment a short inverted repeat element (96 positions) observed in the electronmicroscopic studies (Koller and Delius 1982b). Between the borders of the polymorphic region and the nearby inverted repeat (distance of 179 positions) we retrieved an exact copy of parts of the rDNA leader (105 positions) including 49 positions of the chloroplast trnW gene. A computer search for bacterial type Ori-regions did not reveal any significant sequence homology. However, the polymorphic region and its immediate vicinity have the capacity to form multiple stem and loop structures which may be involved in DNA replication initiation.

1982, Keller, Mario, Stutz, Erhard

The DNA fragment Eco-I (4700 kilobasepairs) from the circular chloroplast genome of Euglena gracilis is shown to be transcribed in etioplasts at all stages of light-induced plastid development and in fully differentiated chloroplasts. Major stable transcription products are mRNAs of 14S and 17S. Using a rabbit reticulocyte lysate translation system we can show that the fragment Eco-I selects a mRNA which directs the synthesis of a M_r 32 000–33 000 polypeptide. Eco-I also hybridizes with a 330 basepair DNA probe cut from within the spinach chloroplast gene encoding the M_r 32 000 thylakoid membrane protein of the photosystem II reaction center. We conclude that the fragment Eco-I carries the corresponding Euglena gracilis chloroplast gene.