Division Chlorarachniophyta

Abstract

Chlorarachniophyte algae contain a complex, multi-membraned chloroplast derived from the endosymbiosis of a eukaryotic alga. Phylogenetic trees indicate that the host is closely related to filose amoebae and sarcomonads whereas the endosymbiont is most closely related to green algae. The endosymbiont is greatly reduced retaining only the plastid, plasmamembrane, a modicum of cytoplasm, and the nucleus. The vestigial nucleus of the endosymbiont, called the nucleomorph, contains three small linear chromosomes with a haploid genome size of 380 kb and is the smallest known eukaryotic genome. The overall gene organisation of the nucleomorph genome is extraordinarily compact making this a unique m..