Nucleolar chromatin organization at different activities of soybean root meristematic cell nucleoli

Abstract

Nucleolar chromatin, including nucleolus-associated chromatin as well as active and inactive condensed ribosomal DNA (rDNA) chromatin, derives mostly from secondary constrictions known as nucleolus organizer regions containing rDNA genes on nucleolus-forming chromosomes. This chromatin may occupy different nucleolar positions being in various condensation states which may imply different rDNA transcriptional competence. Sections of nucleoli originating from root meristematic cells of soybean seedlings grown at 25 °C (the control), then subjected to chilling stress (10 °C), and next transferred again to 25 °C (the recovery) were used to measure profile areas occupied by nucleolar condensed chromatin disclosed with sodium hydroxide methylation–acetylation plus uranyl acetate technique. The biggest total area of condensed chromatin was found in the nucleoli of chilled plants, while the smallest was found in those of recovered plants in relation to the amounts of chromatin in the control nucleoli. The condensed nucleolar chromatin, in the form of different-sized and different-shaped clumps, was mainly located in fibrillar centers. One can suppose that changes of condensed rDNA chromatin amounts might be a mechanism controlling the number of transcriptionally active rDNA genes as the nucleoli of plants grown under these experimental conditions show different transcriptional activity and morphology.

Cytogenetic characteristic of the Caucasian pygmy shrew (Sorex volnuchini) and Levant mole (Talpa levantis) (Mammalia: Eulipotyphla) in northern Anatolia, Turkey

“…However, Ag-NOR is widely used in many taxonomic groups (Dobigny et al, 2002). In addition, although NORs can be determined by silver staining, they can be in the form of secondary constrictions, which are active transcript regions on the metaphase chromosomes (Godpasture and Bloom, 1975;Rao et al, 2005;Caperta et al, 2007;Stepinski, 2013). According to the standard staining results of the karyotype of S. volnuchini, the secondary constriction is present on the long arm of chromosome pairs no.…”

“…In mammals, subunits encoded by rDNA include 18S, 5.8S, and 28S rRNA units (Cazaux et al, 2011). Because species-specific rDNA clusters located on the chromosome are found in different regions and numbers, they are frequently used in phylogenetic and mammalian systematics (DavidianBritton et al, 2012;Stepinski, 2013). Since silver stains the NOR-associated proteins on the chromosomes, NORs can be determined by silver staining (Rao et al, 2005).…”

Functional ultrastructure of the plant nucleolus

“…Lots of studies have been carried out on nucleolar chromatin identification and its arrangement in interphase and mitotic cells using different techniques mostly at the electron microscope level (Thiry et al 1991 ; Risueño and Testillano 1994 ), including DNA immunogold detection with the use of monoclonal anti-DNA antibody (Yano and Sato 2002 ), in situ terminal deoxynucleotidyl transferase–immunogold (TdT) (Mineur et al 1998 ), in situ hybridization with probes to characteristic rDNA sequences (Thiry and Thiry-Blaise 1989 ), as well as distinct staining methods, including osmium ammine-B complex (Motte et al 1991 ; Biggiogera et al 1996 ) as well as NAMA–Ur technique (Fig. 3b, d ) (Testillano et al 1991 ; Long et al 2008 ; Shang et al 2009 ; Stępiński 2013 ). Despite using various techniques and different research models, the results of studies concerning nucleolar chromatin localization and structure are fairly consistent.…”

“…It means that the content of nucleolar-condensed chromatin can change according to the transcriptional activity of nucleoli. Indeed, such a correlation was observed in the nucleoli of soybean plants subjected to chilling, when nucleolar transcriptional activity was low, the increase in the content of condensed chromatin was observed, whereas when the seedlings were transferred from chilling to the optimal growth temperature to recover then the nucleoli showed extra high activity and the amount of the condensed chromatin decreased in comparison to the situation when the plants grew continuously at optimal temperature where nucleolar transcriptional activity was at the normal level and the nucleolar-condensed chromatin content was intermediate (Stępiński 2012b , 2013 ). Moreover, it is hypothesized that in the nucleoli with growing transcriptional activity in which ribosomal genes are transcribed continuously, the temporarily inactive chromatin, residing in FCs in the decondensed state, might be ready to use (Risueño et al 1982 ).…”

A análise do interactoma de SCI1 (Stigma/Style Cell Cycle Inhibitor 1) revela possíveis mecanismos de controle da proliferação celular

“…Mediator é um complexo multiprotéico, que atua como uma interface para transmitir a mensagem dos fatores de transcrição para uma unidade transcricional basal, estruturada na região promotora de genes específicos, promovendo a ativação/repressão transcricional dos mesmos (Mathur et al, 2011). (Deltour et al, 1986), Zea mays (Motte et al, 1988) e Glycine max (Stępiński et al, 2013).…”