O. Pontes et al., Physical mapping, expression patterns and interphase organisation of rDNA loci in Portuguese endemic Silene cintrana and Silene rothmaleri, CHROMOS RES, 8(4), 2000, pp. 313-317
Double target in situ hybridization to root tip metaphase and interphase ce
lls of Silene cintrana and Silene rothmaleri was used to allocate the posit
ion of 18S-5.8S-25S and 5S rRNA genes. In both species, the 18S-5.8S-25S rD
NA probe labelled four sites located on the short arms of two submetacentri
c chromosomes. Only one locus for 5S rDNA was mapped adjacent to 18S-5.8S-2
5S genes in a subterminal position on the centromere side: in S. rothmaleri
the 5S rDNA locus was adjacent to the small 18S-5.8S-25S locus while in S.
cintrana it was near the large one. The NOR activity analysed by Ag-staini
ng in metaphase cells revealed proportionality between in situ labelling di
mensions and Ag-NORs. In both species all rDNA loci were potentially active
, although in S. rothmaleri a tendency for the expression of only one locus
was observed. Interphase organisation analysis of rDNA showed some differe
nces between both species that were correlated with NOR activity.