A karyotypic study of three southern Brazilian Asteraceae species using fluorescence in situ hybridization with a 45S rDNA probe and C-CMA3 banding

Abstract

The Asteraceae, one of the largest families of flowering plants, contains about 1,100 genera and 20,000 species, and is well known for its extensive karyotypic variation. In this study, conventional Feulgen staining, C-CMA 3 banding, and fluorescence in situ hybridization with a 45S rDNA probe were used to determine the chromosome number and the number and physical position of GC-rich heterochromatin and 45S rDNA sites in three Asteraceae weed species (Crepis japonica, Galinsoga parviflora and Chaptalia nutans). The three species exhibited karyotype differences in the chromosome number and shape, as a commom feature of Asteraceae. However, the 45S rDNA sites always occurred on the short chromosomal arms, associated with GC-heterochromatin. Althought of these differences, it suggests that commom features of plant karyotype are maintained.

Contenido de ADN y patrón de genes ribosomales en el género monotípico Stetsonia (Cactaceae).

“…En plantas el bandeo cromosómico fluorescente , también ha sido reportado en otras familias como Asteraceae y Solanaceae (Fregonezi et al, 2004;Ruas et al, 2005;Moreno et al, 2012). Además, se reportó la localización de ADNr 5S en un par cromosómico en posición pericentromérica, coincidiendo con las demás especies de Angiospermas (Kulak et al, 2002).…”

Karyotype characterization of two populations of Vernonia geminata (Asteraceae, Vernonieae) using banding and FISH techniques

“…In this chromosome, only one 45S rDNA site was observed in the centromeric region of the short arm ( Figures 1A and 2). Different numbers of 45S rDNA sites and CMA + bands were previously observed in Cestrum L. (Fregonezi et al, 2004), Helianthus L. (Vanzela et al, 2002) and Crotalaria L. (Mondim et al, 2007). According to Mondim et al (2007), in Crotalaria, CMA + bands could not be visualized due to the reduced size of its chromosomes.…”

“…Lima-de Faria (1976) suggested that 45S rDNA sites in short arm of chromosomes are a general trend within the Asteraceae. Studies involving FISH of 45S rDNA in species of this family have also shown this trend (Vanzela et al, 2002;Torrel et al, 2003;Garnatje et al, 2004;Fregonezi et al, 2004).…”

“…The results of the present study are still premature to conclude which mechanisms are involved in Vernonia. The FISH technique is more qualitative than quantitative, but an association between the size of the FISH sites and the number of repeated sequences of rDNA can be demonstrated, and thus, more intense signals represent small sites with a larger number of repeated sequences of less intense signals (Fregonezi et al, 2004). Lima-de Faria (1976) suggested that 45S rDNA sites in short arm of chromosomes are a general trend within the Asteraceae.…”

“…The FISH was done according to Cuadrado and Jouve (1994), with the modifications of Fregonezi et al (2004). The pTa71 probe (18S-5.8S-26rDNA) was labeled by nick translation (Bionick Gibco kit) with biotin-14dATP.…”