The occurrence of different Bs in <i>Cestrum intermedium</i> and <i>C. strigilatum</i> (Solanaceae) evidenced by chromosome banding

Abstract

In this study, we examine the morphology, mitotic stability, meiotic behavior and the composition of heterochromatin of B chromosomes in Cestrum intermedium and C. strigilatum. The results showed that B chromosome number shows intraindividual variation in the root meristem, which seems to lead to a slight rate of B elimination in this somatic tissue. B chromosomes in both species were similar in size and shape, but differed with regard to the type, size and distribution of heterochromatin. Possible evolutionary pathways for B chromosome origin in Cestrum are discussed.

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

“…The size of Bs in Cestrum is 3-5 fold lower than A-chromosomes, as usually reported in plants (Jones and Houben 2003). The morphology of Bs in Cestrum is similar, but differences in composition and size of heterochromatin blocks suggest that they have been originated independently from each other (Fregonezi et al 2004). This hypothesis needs to be verified, since the variation in heterochromatin observed in the Bs may be also explained by their rapid evolution (Houben et al 2014), which make them subject of structural changes such as accumulation of repetitive DNAs (Lamb et al 2007;Klemme et al 2013).…”

“…These supernumerary chromosomes had been observed in C. intermedium and C. strigilatum by Fregonezi et al (2004), and in a hybrid Cestrum (C. parqui x C. aurantiacum) by Sykorova et al (2003b). In C. euanthes, C. nocturnum, and C. parqui, Bs varied in number at both intra-and interindividual level, which indicates possible mechanisms of mitotic and/or meiotic instability (Camacho et al 2000).…”

“…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).…”

Distribution of a Ty3/gypsy-like retroelement on the A and B-chromosomes of Cestrum strigilatum Ruiz & Pav. and Cestrum intermedium Sendtn. (Solanaceae)

“…In our study, C. strigilatum and C. intermedium showed a diffuse distribution of the pCs12 probe, indicating that the Ty3-gypsy retroelements also occur distributed along the chromosomes. Besides this general dispersed tendency, both species exhibited a concentration of these elements in some terminal regions, associated with NORs, which are also associated with GC-rich heterochromatin (Fregonezi et al, 2004). Retroelements have previously been reported to be associated with the NORs of some Triticeae (Belyayev et al, 2001), with the heterochromatin of Allium cepa (onion) (Pearce et al, 1996) and A. thaliana , and with centromeric regions in several monocotyledons (Kumar and Bennetzen, 1999) and dicotyledons (Santini et al, 2002).…”

“…The Cestrum group is an interesting plant group because it possesses genomes with different heterochromatin families, such as C-Giemsa bands, GC-rich bands associated Genetics and Molecular Biology, 30, 3, 599-604 (2007) Copyright by the Brazilian Society of Genetics. Printed in Brazil www.sbg.org.br with nucleolar organizing regions (NORs), GC-rich bands not NOR-associated, AT-rich bands associated with cold sensitive regions (CSRs), C-Giemsa/CSR/AT -bands and C-GC/AT neutral bands (see Berg and Greilhuber, 1992, 1993a, 1993b, Fregonezi et al, 2004, Fregonezi et al, 2006.…”