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Start Over Author "Thiry, M" Publisher elsevier bv
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13. Nucleolar structure across evolution: The transition between bi- and tricompartmentalized nucleoli lies within the class Reptilia

Author

Denis L. J. Lafontaine, Sonia Galliot, Lorenzo Alibardi, Marc Thiry, Françoise Lamaye, Lamaye F., Galliot S., Alibardi L., Lafontaine D.L.J., and Thiry M.

Subjects
Male, Dense fibrillar component, Class Reptilia, Nucleolus, cells, genetic processes, macromolecular substances, Biology, environment and public health, Microscopy, Electron, Transmission, nucleolou, Structural Biology, Animals, Intestinal Mucosa, Transition (genetics), Reptiles, Antigens, Nuclear, DNA, Biological Evolution, ultrastructure, Molecular biology, Chromatin, reptile, Cajal body, Evolutionary biology, Ultrastructure, Cytochemistry, Cell Nucleolus
Abstract

Two types of nucleolus can be distinguished among eukaryotic cells: a tri-compartmentalized nucleolus in amniotes and a bi-compartmentalized nucleolus in all the others. However, though the nucleolus' ultrastructure is well characterized in mammals and birds, it has been so far much less studied in reptiles. In this work, we examined the ultrastructural organization of the nucleolus in various tissues from different reptilian species (three turtles, three lizards, two crocodiles, and three snakes). Using cytochemical and immunocytological methods, we showed that in reptiles both types of nucleolus are present: a bi-compartmentalized nucleolus in turtles and a tri-compartmentalized nucleolus in the other species examined in this study. Furthermore, in a given species, the same type of nucleolus is present in all the tissues, however, the importance and the repartition of those nucleolar components could vary from one tissue to another. We also reveal that, contrary to the mammalian nucleolus, the reptilian fibrillar centers contain small clumps of condensed chromatin and that their surrounding dense fibrillar component is thicker. Finally, we also report that Cajal bodies are detected in reptiles. Altogether, we believe that these results have profound evolutionarily implications since they indicate that the point of transition between bipartite and tripartite nucleoli lies at the emergence of the amniotes within the class Reptilia.

Published
2011
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