Heterochromatin differentiation in holocentric chromosomes of Rhynchospora (Cyperaceae)

Abstract

Holocentric chromosomes of six species of Rhynchospora, R. ciliata, R. pubera, R. riparia and R. barbata (2n = 10), R. nervosa (2n = 30) and R. globosa (2n = 36), were stained with CMA3/DAPI fluorochromes or treated with C-banding and sequentially stained with Giemsa or CMA3/DAPI. Variability in banding pattern was found among the species studied. Heterochromatin was observed on terminal and interstitial chromosome regions, indicating that the holocentric chromosomes of Rhynchospora show a heterochromatin distribution pattern similar to those plant monocentric chromosomes.<br>Cromossomos holocêntricos de seis espécies de Rhynchospora (R. ciliata, R. pubera, R. riparia e R. barbata (2n = 10), R. nervosa (2n = 30) and R. globosa (2n = 36)) foram corados com os fluorocromos CMA3/DAPI ou tratados para bandeamento C e seqüencialmente corados com Giemsa ou CMA3/DAPI. Variabilidade no padrão de bandas foi encontrada entre as espécies estudadas. A heterocromatina foi observada em regiões terminais e intersticiais dos cromossomos, indicando que os cromossomos holocêntricos de Rhynchospora mostram um padrão de distribuição de heterocromatina similar àqueles dos cromossomos monocêntricos de plantas

Neocentrics and Holokinetics (Holocentrics): Chromosomes out of the Centromeric Rules

“…On the contrary, holokinetic chromosomes are homogenously condensed having neither primary constrictions nor heterochromatin-rich pericentromere organization. The amount and distribution of heterochromatin in holokinetic chromosomes, identified by C-banding or the base-specific fluorochromes chromomycin A3 (CMA) and 4,6-diamidino-2-phenylindole (DAPI), are quite variable, as they are in monocentric chromosomes [see, e.g., Sheikh and Kondo, 1995;Vanzela and Guerra, 2000;Guerra and García, 2004]. In L. nivea , a 178-bp tandemly repeated sequence, isolated by homology with the 155-bp rice centromeric sequence, was localized by FISH in up to 5 major clusters on each chromosome [Haizel et al, 2005].…”

“…The 4 individualized distinct chromatids are simultaneously pulled apart generating a single localized region of tension in each chromatid ( fig. 3 e), characterizing a 'box configuration' [see, e.g., Nordenskiöld, 1962a;Pazy and Plitmann, 1987;Vanzela et al, 2000;Guerra and García, 2004]. Several authors have claimed that at anaphase I, the sister chromatids segregate to different poles whereas the homologous chromatids fall apart at anaphase II, characterizing the socalled 'inverted meiosis' [reviewed by Mola and Papeschi, 2006].…”

“…Three of the 5 chromosome pairs of R. pubera have a terminal site of 45S rDNA ], also differentiated as weak CMA + bands [Vanzela and Guerra, 2000], which help to identify the bivalent orientation. The mitotic metaphase ( fig.…”

Karyotype characterization of planthopper species Hysteropterum albaceticum Dlabola, 1983 and Agalmatium bilobum (Fieber, 1877) (Homoptera: Auchenorrhyncha: Issidae) using AgNOR-, C- and DAPI/CMA3 -banding techniques

“…In recent years however an increasing quantity of such data have appeared and shown that holokinetic chromosomes can display a great deal of C-heterochromatin (Blackman, 1976(Blackman, , 1990Kuznetsova et al 1997;Maryańska-Nadachowska, 1999;Vanzela et al, 2000;Grozeva, Nokkala, 2001;Golub et al, 2004;Angus et al, 2004;Pérez et al, 2005;Franco et al, 2006;Bressa et al, 2008;Maryańska-Nadachowska et al, 2008). The species can diverge considerably in this pattern: some display a lot of C-heterochromatin; some show prominent C-bands of different size in separate chromosomes; and in other species C-heterochromatin appeared to avoid detection due to its presence in small or minute amounts.…”

Evidence of genetic differentiation and karyotype evolution of the sedges Cyperus ligularis L. and C. odoratus L. (Cyperaceae)

“…Contrasting with the significant amount of published data on the karyological features of some genera of Cyperaceae, such as Carex, Eleocharis and Rhynchospora (Vanzela & Guerra 2000;Roalson 2008;Silva et al 2010;Cabral et al 2014), very little is known about the chromatin organization in Cyperus species. In fact, to the best of our knowledge, this is the first time that heterochromatic regions are evidenced in chromosomes of Cyperus species by means of fluorochrome banding.…”