Algae. 2000; 15(1): 1-5.

A Molecular Phylogenetic Perspective on the Primary and Secondary and Secondary Endosymbiotic Origins of Algal Plastids

Debashish Bhattacharya

Algae include all photosynthetic eukaryotes excluding land plants. The algae are of a polyphyletic origin and have gained their photosynthetic organelles (plastids) through symbiosis. In this review I present evidence that supports the idea that a single primary symbiosis involving a cyanobacterium gave rise to a proto-alga that was the common ancestor of the three primary algal lineages (Chlorophyta, Rhodophyta, Glaucocystophyta). Members of the Chlorophyta and Rhodophyta then gave rise to all other algal plastids through secondary symbioses. All secondary symbioses appear to be independent events involving different algal synbionts. This hypothesis is supported origins of the secondary plastids of the Cryptophyta, Haptophyta, and Heterokonta.

Keywords : actin, algal evolution, plastid, primary symbiosis, ribosomal RNA, secondary symbiosis