title: Genome composition in Venezuelan spiny-rats of the genus Proechimys(Rodentia, Echimyidae). I. Genome size, C-heterochromatin and repetitive DNAs in situ hybridization patterns.
abstract: The genome sizes of the Venezuelan spiny-rats Proechimys guairae guairae (2n = 48) and P. trinitatis (2n = 62) were evaluated and proved to be 12.5 +/- 0.5 pg and 12.6 +/- 0.3 pg respectively, the highest so far recorded among mammals; also the C-heterochromatin (32.7%, Coefficient of Variation [CV] 3.8 and 35.8%, CV 4.4) and GC (44.2%, CV 2.7 and 43.6%, CV 2.9) contents are very high. Highly repetitive (rep) DNAs were isolated from restriction enzyme digested genomic DNAs of both species. The intra- and inter-specific chromosomal allocations of these rep DNAs were analyzed by direct and cross-hybridizations. Results show that the two genomes harbour several rep DNA families which show both species-specificity and interspecific relatedness in their in situ hybridization patterns. The rep DNA families show an equilocal distribution at both the pericentromeric areas of all chromosomes and in the whole arms of two pairs of the uniarmed group, suggesting co-evolution of the rep DNAs. P. g. guairae BamHI digested DNA, when cloned and sequenced, proved to consist of a long "composite" unit (1,239 bp) containing two copies of each of 75-bp and 110-bp internal subrepeats. Karyotype restructuring between P. g. guairae and P. trinitatis, mainly due to Robertsonian changes, was accompanied by slight intra- and intergenomic movements of the putative satellite DNA families within stable genome sizes and C-heterochromatin contents. We discuss the findings obtained in Proechimys in the light of those regarding the kangaroo rat, the pocket gopher and the house mouse; they support the idea that karyotype restructuring could be the expression of molecular driven events of rep DNA amplification and homogenisation through non-homologous chromosomes.
authors.affiliation: Dipartimento di Biologia Animale e Centro di Studio per l'Istochimica del CNR, Università di Pavia, Italy. Garagna@ipv36.unipv.it
authors.forename: S
authors.initials: S
authors.lastname: Garagna
authors.forename: A
authors.initials: A
authors.lastname: Pérez-Zapata
authors.forename: M
authors.initials: M
authors.lastname: Zuccotti
authors.forename: S
authors.initials: S
authors.lastname: Mascheretti
authors.forename: N
authors.initials: N
authors.lastname: Marziliano
authors.forename: C A
authors.initials: CA
authors.lastname: Redi
authors.forename: M
authors.initials: M
authors.lastname: Aguilera
authors.forename: E
authors.initials: E
authors.lastname: Capanna
mesh_terms: D000818:Animals; D001483:Base Sequence; D006690:Bisbenzimidazole; D002871:Chromosome Banding; D004247:DNA / Q000032:analysis; D015245:Deoxyribonuclease BamHI; D015252:Deoxyribonucleases, Type II Site-Specific; D004173:Dipodomys; D019143:Evolution, Molecular; D005260:Female; D005456:Fluorescent Dyes; D016678:Genome; D006570:Heterochromatin / Q000235:genetics*; D017404:In Situ Hybridization, Fluorescence; D007364:Intercalating Agents; D007621:Karyotyping; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D008969:Molecular Sequence Data; D008926:Plicamycin / Q000031:analogs & derivatives; D012091:Repetitive Sequences, Nucleic Acid; D015183:Restriction Mapping; D012377:Rodentia / Q000235:genetics*; D013045:Species Specificity
chemical_list: D005456:Fluorescent Dyes; D006570:Heterochromatin; D007364:Intercalating Agents; D004247:DNA; C066851:mithramycin A; D015245:Deoxyribonuclease BamHI; C025630:CAGCTG-specific type II deoxyribonucleases; D015252:Deoxyribonucleases, Type II Site-Specific; C032262:GGNCC-specific type II deoxyribonucleases; C040158:GTAC-specific type II deoxyribonucleases; D006690:Bisbenzimidazole; D008926:Plicamycin