, Volume 237, Issue 2, p 379
Date: 19 Dec 2012

Special issue on evolution and biogenesis of chloroplasts and mitochondria

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Mitochondria and chloroplasts are both of endosymbiotic origin. In an initial step about 1.5–2.0 billion years ago an α-proteobacterium was taken up into an undisclosed host cell and enslaved to become mitochondrion. Later a mitochondria containing cell took up an ancestral photosynthetic cyanobacterium, which became a chloroplast. Both primary endosymbiotic events occurred successfully only once in evolution. During the endosymbiotic process, massive gene transfer to the host nucleus and gene loss occurred. The arising eukaryotic cell took the chance from combining three genomes to establish a division of labour principle in the newly compartmentalised cell. Though mitochondria and chloroplasts have retained a remnant genome and the capacity for transcription and translation, the control lies with the nucleus. Organellar genomes have been retained throughout all eukaryotic life forms with very few exceptions. The reasons for this are not completely understood.

Anabolic and catabolic bi