title: Morphological Studies of Nucleologenesis in Giardia lamblia.
abstract: The nucleolus is a nuclear organelle involved in ribosome biogenesis. In most eukaryotes this structure disperses during prophase through anaphase and reorganizes at telophase by a process known as nucleologenesis. This process involves new transcription of ribosomal DNA at the nucleolar organizer region and the formation of prenucleolar bodies fusing to it. In Giardia lamblia, for a long time considered the only anucleolated eukaryote, a very small nucleolus has been recently described. In order to evaluate whether nucleologenesis is also present in Giardia, we analyzed the distribution of nucleolar material during telophase using different light and electron microscopy techniques including silver staining for the nucleolar organizer. Results indicate that in G. lamblia, nucleolar elements persist mainly as an intranuclear peripheral organelle during all stages of division, including telophase, however, no prenucleolar bodies are detected in the nucleoplasm. Therefore, in the parasite, nucleolar material is present throughout cell division including telophase and formation of prenucleolar bodies may not be required for nucleologenesis.
authors.affiliation: Department of Cell Biology, Faculty of Sciences, UNAM, México City, México.
authors.forename: Reyna
authors.initials: R
authors.lastname: Lara-Martínez
authors.affiliation: Department of Cell Biology, Faculty of Sciences, UNAM, México City, México.
authors.forename: María
authors.initials: M
authors.lastname: De Lourdes Segura-Valdez
authors.affiliation: Laboratory of Genetic Biochemistry, National Institute of Pediatrics, México City, México.
authors.forename: Ignacio
authors.initials: I
authors.lastname: De La Mora-De La Mora
authors.affiliation: Laboratory of Genetic Biochemistry, National Institute of Pediatrics, México City, México.
authors.forename: Gabriel
authors.initials: G
authors.lastname: López-Velázquez
authors.affiliation: Department of Cell Biology, Faculty of Sciences, UNAM, México City, México.
authors.forename: Luis Felipe
authors.initials: LF
authors.lastname: Jiménez-García
mesh_terms: D002466:Cell Nucleolus / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D002467:Cell Nucleus / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D004275:DNA, Ribosomal / Q000378:metabolism; D016829:Giardia lamblia / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D008938:Mitosis / Q000502:physiology*; D009687:Nuclear Proteins / Q000378:metabolism; D009697:Nucleolus Organizer Region / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D004275:DNA, Ribosomal; D009687:Nuclear Proteins
keywords: Giardia lamblia; nucleolar organizer region; nucleologenesis; nucleolus