Chloroplast history clarified by the criterion of light-harvesting complex

Bacterial essence of mitochondria and chloroplasts was initially proclaimed in general outline. Later, the remarkable insight gave way to an elaborate hypothesis. Finally, it took shape of a theory confirmed by molecular biology data. In particular, the rrn operon, which is the key phylogeny marker, locates chloroplasts on the tree of Cyanobacteria. Chloroplast ancestry and diversity can be also traced with the rpoС and psbA genes, rbc operon, and other molecular criteria of prime importance. Another criterion, also highly reliable, is light-harvesting complex (LHC). LHC pigment and protein moieties specify light acclimation strategies in evolutionary retrospect and modern biosphere. The onset of symbiosis between eukaryotic host and pre-chloroplast, as well as further mutual adjustment of partners depended on physiological competence of LHC. In this review, the criterion of LHC is applied to the origin and diversity of chloroplasts. In particular, ancient cyanobacterium possessing tandem antenna (encoded by the cbp genes and the pbp genes, correspondingly), and defined as a prochlorophyte, is argued to be chloroplast ancestor.