Protoplasma

, Volume 127, Issue 1, pp 9–20

DNA is present in the nucleomorph of cryptomonads: Further evidence that the chloroplast evolved from a eukaryotic endosymbiont

  • Martha Ludwig
  • Sarah P. Gibbs
Article

DOI: 10.1007/BF01273697

Cite this article as:
Ludwig, M. & Gibbs, S.P. Protoplasma (1985) 127: 9. doi:10.1007/BF01273697

Summary

The nucleomorph is a unique self-replicating organelle which is invariably present in the periplastidal compartment of cryptomonads. The nucleomorph ofCryptomonas abbreviata is located in a groove on the inner face of the pyrenoid. When JB-4-embedded sections ofC. abbreviata are stained with 4′-6-diamidino-2-phenylindole (DAPI), the nucleomorph exhibits a blue fluorescence characteristic of DNA-DAPI complexes. This fluorescence is removed by DNase digestion, but not by RNase. When cells are prepared for electron microscopy by the method of Ryter and Kellenberger (Schreil 1964), a network of fine DNA-like fibrils is observed in the nucleomorph matrix. It is estimated that the nucleomorph contains between 108 and 109 daltons of DNA. The presence of DNA in nucleomorphs strongly supports the hypothesis that the nucleomorph is the vestigial nucleus of a eukaryotic endosymbiont. It is postulated that this eukaryotic symbiont was an ancestral red alga or an organism closely related to red algae. The cryptomonad host cell, on the other hand, is not evolutionarily close to any other group of algae.

Keywords

Algal evolution Chloroplast evolution Cryptomonasabbreviata Nucleomorph DNA 

Copyright information

© Springer-Verlag 1985

Authors and Affiliations

  • Martha Ludwig
    • 1
  • Sarah P. Gibbs
    • 1
  1. 1.Department of BiologyMcGillUniversityMontrealCanada