Eukaryotes Genomes - CYANIDIOSCHYON MEROLAE

Cyanidioschyzon merolae is a plastid genome. Plastids are unique organelles found in land plants, algae, and some protozoa. Plastids play important roles in photosynthesis and the biosynthesis of amino acids, fatty acids, vitamins, etc., in the cell. They have their own genetic systems, and their own genomes.

The origin and evolution of plastid genomes, or plastids themselves, have long been an important subject in the biological sciences. Plastids represent the endosymbiotic remnants of a free-living cyanobacterial progenitor, which lost the vast majority of its ancestral cyanobacterial genes after primary plastid endosymbiosis. In order to function, plastids depend on the cell nuclei for most of their proteins and other materials.

The red algae are thought to be one of the basal eukaryotic lineages, and may possess ancestral features of eukaryotic phototrophs. The plastid genomes of the red lineage often contain genes that are involved in the biosynthesis of amino and fatty acids; however, few such genes are present in the plastid genome of the green lineage.

C. merolae is a unicellular red alga that is found in acidic hot springs, it is thought to be one of the most primitive eukaryotes according to many morphological characteristics. The C. merolae cell contains one mitochondrion, one plastid with a centrally located plastid nucleoid, one Golgi body, and one microbody. The first species of algae to be sequenced, the organism consists of a single cell that has three smaller compartments, each containing DNA.

Compact genomes of ultrasmall unicellular algae provide information on the basic and essential genes that support the lives of photosynthetic eukaryotes, including higher plants. C. merolae genome provides a model system with a simple gene composition for studying the origin, evolution and fundamental mechanisms of eukaryotic cells.

References:

Nature 428 (6983) 653-7 (2004)
http://merolae.biol.s.u-tokyo.ac.jp/intro_menu.html
http://abstracts.aspb.org/pb2005/public/P57/8185.html