Plant Molecular Biology 33: 559–564, 1997.
1997 Kluwer Academic Publishers. Printed in Belgium.
Analysis of the ribosomal RNA gene repeat from the moss Funaria
Botanisches Institut, Universit
at Heidelberg, Im Neuenheimer Feld 360, 69120 Heidelberg, Germany
Received 18 June 1996; accepted in revised form 30 September 1996
Key words: Bryophyta, Funaria hygrometrica, intergenic spacer, moss, ribosomal transcription unit
33258-CsCldensity gradient. One of the three DNA-satellite bands(GC
) representedthe ribosomal fraction. After
digestion with EcoRI three larger fragments were obtained which hybridized to the large and small ribosomal
subunits from Sinapis alba. The fragments were cloned and sequenced. The complete ribosomal DNA consists of
11132 bp. The analysis of the 18S, 5.8S and 25S rDNA revealed a high sequence and length similarity to other
plant sequences. An intron of 169 bp situated 10 bp from the 5
end of the 25 S rDNA was found. The intergenic
spacer (IGS) has a length of 5150 bp with 13 highly conserved subrepeats (38 bp except for two of 56 bp) followed
directly by 6 other repeated elements of 42–43 bp. Two putative transcription initiation sites (TIS) were identiﬁed
with some differences to known TIS of angiosperms.
In higher plants, as in animals, rDNA occurs as a
multigene family located in the nucleolus organizing
region (NOR). It occurs as a complex genetic locus
constituted by numerous tandemly arranged copies of
ribosomal RNA genes of highly variable copy num-
ber, at one or more chromosome locations [1, 2]. The
basic organization of ribosomal DNA has been main-
tained in most eukaryotic systems. One repeating unit
consists of the 18S rRNA, ITS
25S rRNA and the IGS. Sometimes regulatory ele-
ments are included in subrepeats of different lengths.
The part of the IGS downstreamfrom the transcription
initiation site (TIS) constitues the external transcribed
spacer. RNA polymerase I is responsible for transcrip-
tion of the 18S-25S rRNA, and the ETS and intern-
al transcribed spacers, which are later removed dur-
ing rRNA processing. The rDNA repeating sequences
exibit an enormous length and sequence heterogeneity
[16, 27]. The coding regionsare highlyconservedboth
in lengthand in their nucleotidesequences. The length
GenBank and DDBJ Nucleotide Sequence Databases under the
accession numbers X80212 and X98013.
and sequence heterogeneities mostly occur in the IGS
region. The length of a rDNA repeat in plant species
varies from ca. 8 kb in Raphanus sativus  to 14–
17 kb in Trillium species and Paris verticillata .
The variation in IGS length is caused by the presence
of varying numbers of subrepeats in the region of the
IGS . Not all species show variation within their
rDNA for repeatunitsize . In this study we present
unit of a bryophyte species.
Materials and methods
The gametophyte stage of Funaria hygrometrica was
Knoop . After 4–6 weeks cultivation the material
was collected and lyophilized for 3 days.