期刊
GENETICS AND MOLECULAR BIOLOGY
卷 33, 期 1, 页码 94-98出版社
SOC BRASIL GENETICA
DOI: 10.1590/S1415-47572009005000103
关键词
cacao; cupuacu; heterochromatin; karyotype; rDNA sites; Theobroma
资金
- Brazilian agencies Conselho Nacional de Desenvolvimento Cienti fico e Tecnologico - CNPq [476444/2006-3, 134809/2006-8]
- Fundacao de Amparo a Ciencia e Tecnologia do Estado de Pernambuco - FACEPE [EDT-0005-05.03/04]
A comparative analysis of mitotic chromosomes of Theobroma cacao(cacao) and T. grandiflorum(cupuacu) was performed aiming to identify cytological differences between the two most important species of this genus. Both species have symmetric karyotypes, with 2n=20 metacentric chromosomes ranging in size from 2.00 to 1.19 mu m (cacao) and from 2.21 to 1.15 mu m (cupuacu). The interphase nuclei of both species were of the arreticulate type, displaying up to 20 chromocentres, which were more regularly shaped in cacao than in cupuacu. Prophase chromosomes of both species were more condensed in the proximal region, sometimes including the whole short arm. Both species exhibited only one pair of terminal heterochromatic bands, positively stained with chromomycin A(3), which co-localized with the single 45S rDNA site. Each karyotype displayed a single 5S rDNA site in the proximal region of another chromosome pair. Heterochromatic bands were also observed on the centromeric/pericentromeric regions of all 20 chromosomes of cacao after C-banding followed by Giemsa or DAPI staining, whereas in cupuacu they were never detected. These data suggest that the chromosomes of both species have been largely conserved and their pericentromeric chromatin is the only citologically differentiated region.
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