Supernumerary heterochromatic segments associated with the nucleolar chromosomes of Pyrgomorpha conica (Orthoptera) contain methylated rDNA sequences

The two nucleolus organizing chromosome pairs of the grasshopper Pyrgomorpha conica can carry a proximal supernumerary heterochromatic segment. We employed different cytological techniques to characterize and analyze the possible origin of this segment. The supernumerary segment and the nucleolus or...

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Bibliographic Details
Published in:Chromosoma 1993-07, Vol.102 (7), p.491-499
Main Authors: Suja, J.A, Antonio, C, Gonzalez-Garcia, J.M, Rufas, J.S
Format: Article
Language:English
Subjects:
amplification
Animals
Biological and medical sciences
cell nucleolus
Chromosome Banding
Cytogenetics
DNA methylation
DNA Restriction Enzymes
DNA, Ribosomal - chemistry
DNA, Ribosomal - genetics
Fundamental and applied biological sciences. Psychology
Genetics of eukaryotes. Biological and molecular evolution
Grasshoppers - genetics
Grasshoppers - ultrastructure
heterochromatin
Heterochromatin - ultrastructure
In Situ Hybridization, Fluorescence
Invertebrata
Karyotyping
Male
Methylation
nucleolus organizer
Nucleolus Organizer Region - ultrastructure
Pyrgomorpha conica
ribosomal DNA
Staining and Labeling
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Summary:The two nucleolus organizing chromosome pairs of the grasshopper Pyrgomorpha conica can carry a proximal supernumerary heterochromatic segment. We employed different cytological techniques to characterize and analyze the possible origin of this segment. The supernumerary segment and the nucleolus organizing regions (NORs) show similar responses after C-banding plus either Giemsa or acridine orange, and chromomycin A3/distamycin A staining to detect GC-rich chromosome regions. Fluorescence in situ hybridization with a biotinylated rDNA probe demonstrated that the segment originated by amplification of the rDNA genes. However, as the silver staining indicates, the ribosomal genes present in the segment are not active since no nucleolus is formed. The use of in situ digestion with the isoschizomeric MspI and HpaII restriction endonucleases and subsequent Giemsa, ethidium bromide or chromomycin A3/distamycin A staining, suggests that the segment has been inactivated by DNA methylation.
ISSN:0009-5915
1432-0886
DOI:10.1007/BF00357105