Molecular Biology Reports

, Volume 37, Issue 4, pp 1897–1912

Nuclear ribosomal spacer regions in plant phylogenetics: problems and prospects



The nuclear ribosomal locus coding for the large subunit is represented in tandem arrays in the plant genome. These consecutive gene blocks, consisting of several regions, are widely applied in plant phylogenetics. The regions coding for the subunits of the rRNA have the lowest rate of evolution. Also the spacer regions like the internal transcribed spacers (ITS) and external transcribed spacers (ETS) are widely utilized in phylogenetics. The fact, that these regions are present in many copies in the plant genome is an advantage for laboratory practice but might be problem for phylogenetic analysis. Beside routine usage, the rDNA regions provide the great potential to study complex evolutionary mechanisms, such as reticulate events or array duplications. The understanding of these processes is based on the observation that the multiple copies of rDNA regions are homogenized through concerted evolution. This phenomenon results to paralogous copies, which can be misleading when incorporated in phylogenetic analyses. The fact that non-functional copies or pseudogenes can coexist with ortholougues in a single individual certainly makes also the analysis difficult. This article summarizes the information about the structure and utility of the phylogenetically informative spacer regions of the rDNA, namely internal- and external transcribed spacer regions as well as the intergenic spacer (IGS).


Internal transcribed spacer (ITS) External transcribed spacer (ETS) Intergenic spacer (IGS) Nuclear ribosomal DNA (rDNA) Phylogenetics 


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Copyright information

© Springer Science+Business Media B.V. 2009

Authors and Affiliations

  1. 1.Department of Plant Sciences and Biotechnology, Georgikon FacultyUniversity of PannoniaKeszthelyHungary
  2. 2.Plant BiologyUniversity of HelsinkiHelsinkiFinland

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