title: Implications for evolution of nuclear structures of animals, plants, fungi and protoctists.
abstract: The evolutionary variations of nuclear structure of animals, plants, fungi and protoctists were studied with electron microscopy by using techniques preferentially staining ribonucleoprotein (RNP) particles and chromatin. A remarkable similarity in the general morphological features of the RNP particles and chromatin arrangement is found in animals, plants and fungi. Important variations of these features were found in protoctists. These observations suggest that major evolutionary changes in the nuclear structure predate the acquisition of plastids by the ancestors of green plants. Once evolved, the nuclear structural pattern is conserved in plants and animals. Among protoctists studied, Kinetoplastida, Cryptomonadida and Volvocida have RNP particles and chromatin arrangement resembling those of plants and animals. These similarities may indicate a common ancestor. Important differences in the nuclear structure among Euglenida, Amebida, Cryptomonadida, Volvocida and Kinetoplastida support the view that Sarcomastigophora is a polyphyletic taxon. For the same reason Kinetoplastida and Euglenida must not be grouped in a monophyletic taxon. We propose that the variations of RNP particles may be related to the initial evolution of post-transcriptional processing.
authors.affiliation: Department of Biology, Faculty of Sciences, U.N.A.M., México D.F.
authors.forename: L F
authors.initials: LF
authors.lastname: Jiménez-García
authors.forename: J M
authors.initials: JM
authors.lastname: Elizundia
authors.forename: B
authors.initials: B
authors.lastname: López-Zamorano
authors.forename: A
authors.initials: A
authors.lastname: Maciel
authors.forename: G
authors.initials: G
authors.lastname: Zavala
authors.forename: O M
authors.initials: OM
authors.lastname: Echeverría
authors.forename: G H
authors.initials: GH
authors.lastname: Vázquez-Nin
mesh_terms: D000818:Animals; D005075:Biological Evolution; D002467:Cell Nucleus / Q000648:ultrastructure*; D056890:Eukaryota / Q000166:cytology; D005658:Fungi / Q000166:cytology; D008854:Microscopy, Electron; D010802:Phylogeny; D059828:Plant Cells; D012261:Ribonucleoproteins / Q000032:analysis*; D013045:Species Specificity
chemical_list: D012261:Ribonucleoproteins