[Evolution of cells].

Life has existed on earth for some 4 x 10(9) years. During most of this time, evolution took place at the level of cell evolution. The cells of presently existing organisms belong to two fundamentally different cell types, protocytes (of bacteria and archaea) and eucytes (of eukarya).

Symbiogenetic evolution of complex cells and complex plastids.

It is generally accepted today that mitochondria and plastids of eukaryotic cells ("eucytes") have their phylogenetic origins in prokaryotic cells ("protocytes") that had been taken up into urkaryotic host cells as intracellular symbionts. This concept, strongly supported (among other evidence) by comparisons of rRNA and protein sequence data, has many important consequences for understanding both cellular evolution and cellular compartmentation. According to the Serial Endosymbiont Theory (SET), the eucyte came about by the formation of stable intracellular symbioses of quite different cells.

Plastid DNA from Pyrenomonas salina (Cryptophyceae): physical map, genes, and evolutionary implications.

Cryptomonads are thought to have arisen from a symbiotic association between a eukaryotic flagellated host and a eukaryotic algal symbiont, presumably related to red algae. As organellar DNAs have proven to be useful tools in elucidating phylogenetic relationships, the plastid (pt) DNA of the cryptomonad alga Pyrenomonas salina has been characterized in some detail. A restriction map of the circular 127 kb ptDNA from Pyrenomonas salina was established.

A eukaryotic genome of 660 kb: electrophoretic karyotype of nucleomorph and cell nucleus of the cryptomonad alga, Pyrenomonas salina.

Cryptomonads are unicellular algae with chloroplasts surrounded by four membranes. Between the inner and the outer pairs of membranes is a narrow plasmatic compartment which contains a nucleus-like organelle called the nucleomorph. Using pulsed field gel electrophoresis it is shown that the nucleomorph of the cryptomonad Pyrenomonas salina contains three linear chromosomes of 195 kb, 225 kb and 240 kb all of which encode rRNAs.

Isolation, physical map and gene map of mitochondrial DNA from the cryptomonad Pyrenomonas salina.

Mitochondrial DNA (mtDNA) from the cryptomonad Pyrenomonas salina was isolated by CsCl-buoyant density centrifugation of whole-cell DNA in the presence of Hoechst dye 33258. mtDNA consists of circular molecules about 47 kb in size as estimated from restriction enzyme analysis. A physical map for six restriction enzymes (Bam HI, Bge I, Eco RI, Pst I, Sac I and Sal I) has been constructed.