Article

Molecular and General Genetics MGG

, Volume 230, Issue 1, pp 155-160

First online:

Demonstration of nucleomorph-encoded eukaryotic small subunit ribosomal RNA in cryptomonads

  • Uwe -G. MaierAffiliated withInstitut für Biologie II, Zellbiologie, Universität Freiburg
  • , Claudia J. B. HofmannAffiliated withInstitut für Biologie II, Zellbiologie, Universität Freiburg
  • , Stefan EschbachAffiliated withInstitut für Biologie II, Zellbiologie, Universität Freiburg
  • , Jörn WoltersAffiliated withInstitut für Allgemeine Mikrobiologie
  • , Gabor L. IgloiAffiliated withInstitut für Biologie III

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Summary

In cryptomonads, unicellular phototrophic flagellates, the plastid(s) is (are) located in a special narrow compartment which is bordered by two membranes; it harbours neither mitochondria nor Golgi dictyosomes but comprises eukaryotic ribosomes and starch grains together with a small organelle called the nucleomorph. The nucleomorph contains DNA and is surrounded by a double membrane with pores. It is thought to be the vestigial nucleus of a phototrophic eukaryotic endosymbiont. Cryptomonads are therefore supposed to represent an intermediate state in the evolution of complex plastids from endosymbionts. We have succeeded in isolating pure nucleomorph fractions, and can thus provide, using pulsed field gel electrophoresis, polymerase chain reaction and sequence analysis, definitive proof for the eukaryotic nature of the symbiont and its phylogenetic origin.

Key words

Cryptomonads Nucleomorph Small subunit ribosomal RNA