Comparative chromosome mapping of repetitive sequences. Implications for genomic evolution in the fish, Hoplias malabaricus.
BACKGROUND
Seven karyomorphs of the fish, Hoplias malabaricus (A-G) were previously included in two major groups, Group I (A, B, C, D) and Group II (E, F, G), based on their similar karyotype structure. In this paper, karyomorphs from Group I were analyzed by means of distinct chromosomal markers, including silver-stained nucleolar organizer regions (Ag-NORs) and chromosomal location of repetitive sequences (18S and 5S rDNA, and satellite 5SHindIII-DNA), through fluorescence in situ hybridization (FISH), in order to evaluate the evolutionary relationships among them.


RESULTS
The results showed that several chromosomal markers had conserved location in the four karyomorphs. In addition, some other markers were only conserved in corresponding chromosomes of karyomorphs A-B and C-D. These data therefore reinforced and confirmed the proposed grouping of karyomorphs A-D in Group I and highlight a closer relationship between karyomorphs A-B and C-D. Moreover, the mapping pattern of some markers on some autosomes and on the chromosomes of the XY and X1X2Y systems provided new evidence concerning the possible origin of the sex chromosomes.


CONCLUSIONS
The in situ investigation of repetitive DNA sequences adds new informative characters useful in comparative genomics at chromosomal level and provides insights into the evolutionary relationships among Hoplias malabaricus karyomorphs.
Cioffi
Marcelo B
MB
Universidade Federal de São Carlos, Departamento de Genética e Evolução, São Carlos, SP, Brazil. mbello.ufscar@gmail.com
Martins
Cesar
C
Bertollo
Luiz A C
LA
D000818:Animals; D002874:Chromosome Mapping / Q000379:methods*; D004275:DNA, Ribosomal / Q000235:genetics; D004276:DNA, Satellite / Q000235:genetics; D019143:Evolution, Molecular; D005399:Fishes / Q000235:genetics*; D005819:Genetic Markers; D016678:Genome; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D009697:Nucleolus Organizer Region / Q000235:genetics; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid; D017422:Sequence Analysis, DNA; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific) / Q000235:genetics
D004275:DNA, Ribosomal; D004276:DNA, Satellite; D005819:Genetic Markers; D012337:RNA, Ribosomal, 18S; C090528:DNA modification methylase HindIII; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific)