Physical mapping of the plastid genome from the chlorophyll c-containing alga,Cryptomonas Φ

Summary A physical map of the circular plastid genome of Cryptomonas has been constructed using the enzymes SacI, BamHI, SmaI, SalI, PstI and XhoI. In addition, fine-structural mapping of the inverted repeat region has been performed using AvaI, BglII, EcoRI and XbaI. The inverted repeat is very small, encompassing no more than 6 kb and containing only genes for the rRNAs. It divides the plastid genome into a small singlecopy region of 12–13 kb which contains genes for phycoerythrin and the 32 kd photosystem II polypeptide, and a large single-copy region of 93–94 kb, giving a total size of 118 kb. The genes for the large subunit of ribulose-1,5-bisphosphate carboxylase (Rubisco) and the beta subunit of ATP synthase CF₁ are encoded in the large single-copy region. The evolutionary significance of the organization of this plastid genome, the first presented from the chlorophyll c-, phycobiliprotein-containing group of algae, is discussed.