Evolution of chromosomes in the genus Pennisetum

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In this study, we investigated chromosome variation of ten Pennisetum species by fluorescence in situ hybridization (FISH) probed with a highly repetitive centromeric satellite and 45S rDNA sequences. We also analyzed genetic relationship using EST microsatellite markers derived from pearl millet. FISH with the centromeric satellite sequence showed strong to medium hybridization signals at the centromeric regions of all the chromosomes in six species, weak signals on two chromosome pairs in one species and no signals in three species. Locations of 45S rDNA varied both in number and strength among the species. Two species showed signals on one chromosome pair, five species on two chromosome pairs, one species on three chromosome pairs and two species on four chromosome pairs. In addition, DAPI staining exhibited heterochromatin blocks at centromeric, telomeric or both regions in the tested species. Prominent signals were observed at telomeric regions in two species. Polymorphism among the EST-microsatellite markers and phylogenetic tree of these species fitted well with the chromosome variation of these species. The discrepancy between the morphological classification and the phylogenetical grouping suggests that the classification of Pennisetum species should also be considered at the genomic level as well as the morphological features.
財団法人染色体学会の論文