Chromosoma

, 118:85

Linkage of 35S and 5S rRNA genes in Artemisia (family Asteraceae): first evidence from angiosperms

  • Sònia Garcia
  • K. Yoong Lim
  • Michael Chester
  • Teresa Garnatje
  • Jaume Pellicer
  • Joan Vallès
  • Andrew R. Leitch
  • Aleš Kovařík
Research Article

DOI: 10.1007/s00412-008-0179-z

Cite this article as:
Garcia, S., Lim, K.Y., Chester, M. et al. Chromosoma (2009) 118: 85. doi:10.1007/s00412-008-0179-z

Abstract

Typically in plants, the 5S and 35S ribosomal DNA (rDNA) encoding two major ribosomal RNA species occur at separate loci. However, in some algae, bryophytes and ferns, they are at the same locus (linked arranged). Southern blot hybridisation, polymerase chain reactions (PCR), fluorescent in situ hybridisation, cloning and sequencing were used to reveal 5S and 35S rDNA genomic organisation in Artemisia. We observed thousands of rDNA units at two–three loci containing 5S rDNA in an inverted orientation within the inter-genic spacer (IGS) of 35S rDNA. The sequenced clones of 26–18S IGS from Artemisia absinthium appeared to contain a conserved 5S gene insertion proximal to the 26S gene terminus (5S rDNA-1) and a second less conserved 5S insertion (5S rDNA-2) further downstream. Whilst the 5S rDNA-1 showed all the structural features of a functional gene, the 5S-rDNA-2 had a deletion in the internal promoter and probably represents a pseudogene. The linked arrangement probably evolved before the divergence of Artemisia from the rest of Asteraceae (>10 Myrs). This arrangement may have involved retrotransposons and once formed spread via mechanisms of concerted evolution. Heterogeneity in unit structure may reflect ongoing homogenisation of variant unit types without fixation for any particular variant.

Supplementary material

412_2008_179_MOESM1_ESM.doc (50 kb)
Table S1Origin and collection data of the specimens studied (DOC 50.0 KB).
412_2008_179_MOESM2_ESM.doc (106 kb)
Fig. S1Sequencing of the IGS clones (Fig. 1) from A. absinthium and A. tridentata. Alignment of the IGS1 (between the 26S and 5S genes) clones was carried out using Clustal X program. The characteristic sequence features are indicated in colours. Blue—26S and 18S rDNA genes; red—5S rDNA genes; dark green—102-bp sub-repeats; light green—248-bp sub-repeats; grey shading—imperfect 5′ inverted repeat from a putative Cassandra element; yellow shading—imperfect (−) strand priming site (DOC 106 KB).
412_2008_179_MOESM3_ESM.doc (638 kb)
Fig. S2Southern blot hybridisation of A. tridentata ssp. wyomingensis genomic DNA digested with different restriction enzymes and hybridised with the 26S and 5S rDNA probes. Note that both probes co-hybridised to the most of the fragments (arrows). The hybridisation of the upper ∼6 kb EcoRV was stronger with the 5S probe than to the 26S probe which can be explained by the presence of 5S tandem repeat (double 5S) in the gene family corresponding to upper band (DOC 638 KB).
412_2008_179_MOESM4_ESM.doc (412 kb)
Fig. S3Dot matrix self comparison of the IGS from A. absinthium clone 8 (window = 21; stringency = 14). TIS, transcription initiation site (DOC 411 KB).

Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  • Sònia Garcia
    • 1
    • 2
  • K. Yoong Lim
    • 3
  • Michael Chester
    • 3
  • Teresa Garnatje
    • 2
  • Jaume Pellicer
    • 1
  • Joan Vallès
    • 1
  • Andrew R. Leitch
    • 3
  • Aleš Kovařík
    • 4
  1. 1.Laboratori de Botànica, Facultat de FarmàciaUniversitat de BarcelonaCataloniaSpain
  2. 2.Institut Botànic de Barcelona(CSIC-ICUB)CataloniaSpain
  3. 3.School of Biological and Chemical Sciences, Queen MaryUniversity of LondonLondonUK
  4. 4.Institute of BiophysicsAcademy of Sciences of the Czech RepublicBrnoCzech Republic

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