Heterochromatin patterns and ribosomal DNA loci distribution in diploid and polyploid Crotalaria species (Leguminosae, Papilionoideae), and inferences on karyotype evolution

Autor(es)

Mondin, Mateus ^[1] ; Aguiar-Perecin, Margarida L. R. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, ESALQ, Dept Genet, BR-13400970 Piracicaba, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: GENOME; v. 54, n. 9, p. 718-726, SEP 2011.
• Citações Web of Science: 7

Resumo

Most Crotalaria species display a symmetric karyotype with 2n = 16, but 2n = 14 is found in Chrysocalycinae subsection Incanae and 2n = 32 in American species of the section Calycinae. Seven species of the sections Chrysocalycinae, Calycinae, and Crotalaria were analyzed for the identification of heterochromatin types with GC- and AT-specific fluorochromes and chromosomal location of ribosomal DNA loci using fluorescent in situ hybridization (FISH). A major 45S rDNA locus was observed on chromosome 1 in all the species, and a variable number of minor ones were revealed. Only one SS rDNA locus was observed in the species investigated. Chromomycin A(3) (CMA) revealed CMA(+) bands colocalized with most rDNA loci, small bands unrelated to ribosomal DNA on two chromosome pairs in Crotalaria incana, and CMA(+) centromeric bands that were quenched by distamycin A were detected in species of Calycinae and Crotalaria sections. DAPI(+) bands were detected in C. incana. The results support the species relationships based on flower specialization and were useful for providing insight into mechanisms of karyotype evolution. The heterochromatin types revealed by fluorochromes suggest the occurrence of rearrangements in repetitive DNA families in these heterochromatic blocks during species diversification. This DNA sequence turnover and the variability in number/position of rDNA sites could be interpreted as resulting from unequal crossing over and (or) transposition events. The occurrence of only one SS rDNA locus and the smaller chromosome size in the polyploids suggest that DNA sequence losses took place following polyploidization events. (AU)

• Processo FAPESP: 03/11289-0 - Estudo da estrutura e evolução do genoma no gênero Crotalaria L. (Leguminosae-Papilonoideae) e alterações cromossômicas em plantas de milho regeneradas in vitro, através do emprego de hibridação in situ
• Beneficiário: Mateus Mondin
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 98/01170-5 - Análise da organização do genoma de alguns grupos de plantas através de técnicas de hibridação molecular in situ para mapeamento de sequências repetitivas de DNA (FISH) e análise de DNA genômico (GISH)
• Beneficiário: Margarida Lopes Rodrigues de Aguiar-Perecin
• Modalidade de apoio: Auxílio à Pesquisa - Temático
• Processo FAPESP: 01/06147-6 - Estrutura dos cromossomos e evolução cariotípica no gênero Crotalaria (Leguminosae)
• Beneficiário: Mateus Mondin
• Modalidade de apoio: Bolsas no Brasil - Doutorado Direto