Division of Environmental and Applied Biology, University of Dundee, Dundee DD1 4HN, UK. j.a.raven@dundee.ac.uk
The complete genome sequences of cyanobacteria and of the higher plant Arabidopsis thaliana leave no doubt that the plant chloroplast originated, through endosymbiosis, from a cyanobacterium. But the genomic legacy of cyanobacterial ancestry extends far beyond the chloroplast itself, and persists in organisms that have lost chloroplasts completely.