Cyanophora paradoxa Genome Elucidates Origin of Photosynthesis in Algae and Plants

Abstract

Plastid Origins: The glaucophytes, represented by the alga Cyanophora paradoxa , are the putative sister group of red and green algae and plants, which together comprise the founding group of photosynthetic eukaryotes, the Plantae. In their analysis of the genome of C. paradoxa , Price et al. (p. 843 ; see the Perspective by Spiegel ) demonstrate a unique origin for the plastid in the ancestor of this supergroup, which retains much of the ancestral diversity in genes involved in carbohydrate metabolism and fermentation, as well as in the gene content of the mitochondrial genome. Moreover, about 3.3% of nuclear genes in C. paradoxa seem to carry a signal of cyanobacterial ancestry, and key genes involved in starch biosynthesis are derived from energy parasites such as Chlamydiae. Rapid radiation, reticulate evolution via horizontal gene transfer, high rates of gene divergence, loss, and replacement, may have diffused the evolutionary signals within this supergroup, which perhaps explains previous difficulties in resolving its evolutionary history.