In this paper we provide further information on the genome organization of Haplopappus gracilis, one of the six angiosperms showing the lowest chromosome number, i.e. 2n=4, by determining the nucleotide sequence of the Intergenic Spacer region of the rRNA genes and its cytological localization on metaphase chromosomes. DNA sequence analysis reveals the occurring of a product of 4,382 bp in length, characterized by the presence of four blocks of different repeated sequences. Our analysis also evidenced putative promoter regions with three Transcription Initiation Sites for Polymerase I, as previously reported in Artemisia absinthium, belonging to the same Asteraceae family. A fluorescent in situ hybridization with the Intergenic Spacer probe indicates the presence of rDNA genes only in the satellited chromosomes of H. gracilis; besides differences in the signal intensity between homologous chromosomes were frequently observed, so suggesting, for these chromosome sites, the presence of a variable number of rDNA gene copies, even if a divergent chromatin organization in corresponding regions can not be ruled out.
|Autori:||Ruffini Castiglione M; Gelati MT; Cremonini R; Frediani M|
|Titolo:||The intergenic spacer region of the rDNA in Haplopappus gracilis (Nutt.) Gray.|
|Anno del prodotto:||2013|
|Digital Object Identifier (DOI):||10.1007/s00709-012-0441-3|
|Appare nelle tipologie:||1.1 Articolo in rivista|