Karyotype differentiation of four Cestrum species (Solanaceae) based on the physical mapping of repetitive DNA

Jéferson Nunes Fregonezi,Thiago Fernandes,André Luís Laforga Vanzela,José Marcelo Domingues Torezan,Ana Odete S Vieira

doi:10.1590/s1415-47572006000100019

Jéferson Nunes Fregonezi, Thiago Fernandes + Show 3 more

Open Access

https://doi.org/10.1590/s1415-47572006000100019

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Abstract

We studied the karyotypes of four Brazilian Cestrum species (C. amictum, C. intermedium, C. sendtnerianum and C. strigilatum) using conventional Feulgen staining, C-Giemsa and C-CMA3/DAPI banding, induction of cold-sensitive regions (CSRs) and fluorescent in situ hybridization (FISH) with rDNA probes. We found that the karyotypes of all four species was 2n = 2x = 16, with, except for the eighth acrocentric pair, a predominance of meta- and submetacentric chromosomes and various heterochromatin classes. Heterochromatic types previously unreported in Cestrum as neutral C-CMA30/DAPI0 bands, CMA3+ bands not associated with NORs, and C-Giemsa/CSR/DAPI- bands were found. The heterochromatic blocks varied in size, number, position and composition. The 45S rDNA probe preferentially located in the terminal and subterminal regions of some chromosomes, while 5S rDNA appeared close to the centromere of the long arm of pair 8. These results suggest that karyotype differentiation can occur mainly due to changes in repetitive DNA, with little modification in the general composition of the conventionally stained karyotype.

Highlights

Along with Vestia (Willd) and Sessea (Ruiz et Pav) the genus Cestrum (L.) is part of the tribe Cestreae
Terminal signals on the short arms of pairs 6 and 8 were detected with fluorescent in situ hybridization (FISH) with the 45S rDNA probe, while FISH with the 5S rDNA probe gave a proximal signal on the long arm of pair 8 (Figures 4A, 4B and 5A)
We found that in situ hybridization with the 45S rDNA probe gave a very similar distribution to that found in C. intermedium

Summary

Introduction

Along with Vestia (Willd) and Sessea (Ruiz et Pav) the genus Cestrum (L.) is part of the tribe Cestreae The genus Cestrum contains about 250 species distributed in the tropical and subtropical regions of the Americas (D’Arcy, 1986) and includes herbs, shrubs and trees up to 12 m in height. Members of this genus are recognized by their actinomorphic flowers with tubular-infundibuliforme corolla, five stamens attached to the corolla tube up to the middle or higher, bilocular ovary with berry-like fruits, few compressed seeds and a straight embryo (Cronquist, 1988). Solanaceae species such as those of the genera Solanum and Capsicum

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