Complete nucleotide sequence of the chlorarachniophyte nucleomorph: Nature's smallest nucleus
AuthorGilson, PR; Su, V; Slamovits, CH; Reith, ME; Keeling, PJ; McFadden, GI
Source TitlePROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
PublisherNATL ACAD SCIENCES
Document TypeJournal Article
CitationsGilson, P. R., Su, V., Slamovits, C. H., Reith, M. E., Keeling, P. J. & McFadden, G. I. (2006). Complete nucleotide sequence of the chlorarachniophyte nucleomorph: Nature's smallest nucleus. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 103 (25), pp.9566-9571. https://doi.org/10.1073/pnas.0600707103.
Access StatusAccess this item via the Open Access location
Open Access at PMChttp://www.ncbi.nlm.nih.gov/pmc/articles/PMC1480447
C1 - Journal Articles Refereed
The introduction of plastids into different heterotrophic protists created lineages of algae that diversified explosively, proliferated in marine and freshwater environments, and radically altered the biosphere. The origins of these secondary plastids are usually inferred from the presence of additional plastid membranes. However, two examples provide unique snapshots of secondary-endosymbiosis-in-action, because they retain a vestige of the endosymbiont nucleus known as the nucleomorph. These are chlorarachniophytes and cryptomonads, which acquired their plastids from a green and red alga respectively. To allow comparisons between them, we have sequenced the nucleomorph genome from the chlorarachniophyte Bigelowiella natans: at a mere 373,000 bp and with only 331 genes, the smallest nuclear genome known and a model for extreme reduction. The genome is eukaryotic in nature, with three linear chromosomes containing densely packed genes with numerous overlaps. The genome is replete with 852 introns, but these are the smallest introns known, being only 18, 19, 20, or 21 nt in length. These pygmy introns are shown to be miniaturized versions of normal-sized introns present in the endosymbiont at the time of capture. Seventeen nucleomorph genes encode proteins that function in the plastid. The other nucleomorph genes are housekeeping entities, presumably underpinning maintenance and expression of these plastid proteins. Chlorarachniophyte plastids are thus serviced by three different genomes (plastid, nucleomorph, and host nucleus) requiring remarkable coordination and targeting. Although originating by two independent endosymbioses, chlorarachniophyte and cryptomonad nucleomorph genomes have converged upon remarkably similar architectures but differ in many molecular details that reflect two distinct trajectories to hypercompaction and reduction.
KeywordsMolecular Evolution; Infectious Diseases
- Click on "Export Reference in RIS Format" and choose "open with... Endnote".
- Click on "Export Reference in RIS Format". Login to Refworks, go to References => Import References