Gene-rich and gene-poor chromosomal regions have different locations in the interphase nuclei of cold-blooded vertebrates |
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Authors: | Concetta Federico Cinzia Scavo Catia Daniela Cantarella Salvatore Motta Salvatore Saccone Giorgio Bernardi |
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Affiliation: | (1) Dipartimento di Biologia Animale “M. La Greca”, University of Catania, Via Androne 81, 95124 Catania, Italy;(2) Laboratorio di Evoluzione Molecolare, Stazione Zoologica “A. Dohrn”, Villa Comunale, 80121 Naples, Italy |
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Abstract: | In situ hybridizations of single-copy GC-rich, gene-rich and GC-poor, gene-poor chicken DNA allowed us to localize the gene-rich and the gene-poor chromosomal regions in interphase nuclei of cold-blooded vertebrates. Our results showed that the gene-rich regions from amphibians (Rana esculenta) and reptiles (Podarcis sicula) occupy the more internal part of the nuclei, whereas the gene-poor regions occupy the periphery. This finding is similar to that previously reported in warm-blooded vertebrates, in spite of the lower GC levels of the gene-rich regions of cold-blooded vertebrates. This suggests that this similarity extends to chromatin structure, which is more open in the gene-rich regions of both mammals and birds and more compact in the gene-poor regions. In turn, this may explain why the compositional transition undergone by the genome at the emergence of homeothermy did not involve the entire ancestral genome but only a small part of it, and why it involved both coding and noncoding sequences. Indeed, the GC level increased only in that part of the genome that needed a thermodynamic stabilization, namely in the more open gene-rich chromatin of the nuclear interior, whereas the gene-poor chromatin of the periphery was stabilized by its own compact structure. |
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