Karyotype differentiation of four Cestrum species (Solanaceae) revealed by fluorescent chromosome banding and FISH

Abstract

The karyotypes of four South American species of Cestrum (C. capsulare, C. corymbosum, C. laevigatum and C. megalophylum) were studied using conventional staining, C-CMA/DAPI chromosome banding and FISH with 45S and 5S rDNA probes. The karyotypes showed a chromosome number of 2n = 2x = 16, with metacentric chromosomes, except for the eighth submeta-to acrocentric pair. Several types of heterochromatin were detected, which varied in size, number, distribution and base composition. The C-CMA + bands and 45S rDNA were located predominantly in terminal regions. The C-CMA + /DAPI + bands appeared in interstitial and terminal regions, and the C-DAPI + bands were found in all chromosome regions. The 5S rDNA sites were observed on the long arm of pair 8 in all species except C. capsulare, where they were found in the paracentromeric region of the long arm of pair 4. The differences in band patterns among the species studied here, along with data from other nine species reported in the literature, suggest that the bands are dispersed in an equilocal and non-equilocal manner and that structural rearrangements can be responsible for internal karyotype diversification. However, it is important to point out that the structural changes involving repetitive segments did not culminate in substantial changes in the general karyotype structure concerning chromosome size and morphology.

Chromosomal differentiation of Tribe Cestreae (Solanaceae) by analyses of 18-5.8-26S and 5S rDNA distribution

“…Our results confirm previous works on Cestrum strigilatum and Sessea regnellii (Fregonezi et al 2006;Fernandes et al 2009) and report new data about distribution of 18-5.8-26S and 5S rDNA sites in C. elegans, C. euanthes, C. fasciculatum, C. kunthii, C. lorentzianum, C. nocturnum, C. parqui, C. tomentosum, and Vestia foetida. All species studied of Cestreae have conserved the terminal and pericentromeric positions for 18-5.8-26S and 5S rDNA, respectively.…”

“…The basic number x = 8 is conserved in Cestreae and differentiates it from other Solanaceae. Our results confirm previous numbers of several species from other localities (Tschischow 1956;Sharma and Sharma 1957;Bolkhovskikh et al 1969;Moscone 1992;Las Peñas et al 2006;Fregonezi et al 2006;Fernandes et al 2009), being the first chromosome number report for Cestrum euanthes, C. kunthii, C. lorentzianum, and C. tomentosum.…”

“…Tribe Cestreae is additionally characterized by large chromosomes and symmetrical karyotypes (Fregonezi et al 2006;Las Peñas et al 2006;Fernandes et al 2009). Karyotypes of the studied species are relatively symmetrical, have similar chromosome sizes, and are composed exclusively of m chromosomes (Vestia foetida) or with one sm pair (the remaining species).…”

“…a Cestrum nocturnum, b C. parqui, c C. euanthes. Bar = 1 lm species of Cestrum studied to date (Fregonezi et al 2006;Fernandes et al 2009;this work). On the contrary, the 18-5.8-26S rDNA distribution allows to define two groups in Cestrum: one characterized by the synteny of the rDNA in the only sm pair (C. amictum, C. corymbosum, C. elegans, C. fasciculatum, C. intermedium, C. nocturnum, and C. strigilatum), and another one with a 18-5.8-26S rDNA distribution independent of the 5S rDNA loci (C. euanthes, C. kunthii, C. laevigatum, C. lorentzianum, C. megalophylum, C. parqui, C. sendtnerianum, and C. tomentosum).…”

“…Karyotypically, Cestreae is outstanding within Solanaceae because of the following features, which support its monophyly and make it of interest to study karyotype evolution and diversity of distribution of repetitive DNA sequences: (1) basic number x = 8 (Tschischow 1956;Bolkhovskikh et al 1969;Goldblatt 1984;Goldblatt andJohnson 1991, 1996;Las Peñas et al 2006); (2) largest chromosome sizes among the family (Fernandes et al 2009;Fregonezi et al 2006;Las Peñas et al 2006); (3) complex patterns of heterochromatin in Cestrum, like the cold-sensitive regions Greilhuber 1992, 1993;Fregonezi et al 2006); (4) occurrence of B-chromosomes in several Cestrum species with particular banding patterns (Fregonezi et al 2004) and distribution of 45S and 5S rDNA (Sykorova et al 2003b;Fernandes et al 2009); and (5) absence of Arabidopsis-type (TTTAGGG)n telomeres, which seem to be replaced by an A/T-rich minisatellite (Sykorova et al 2003a, b).…”