Cytogenetic analysis on the holocentric chromosomes of the cabbage aphid Brevicoryne brassicae

Chromatin organization in the holocentric chromosomes of the aphid Brevicoryne brassicae has been investigated at a cytological level after C-banding, NOR, Giemsa, DAPI and CMA(3) staining. C-banding technique showed the presence of heterochromatic bands on both telomeres of the two X chromosomes, whereas only the longest pair of autosomes show distinct intercalary C-positive bands. Moreover, silver staining and fluorescent in situ hybridization (FISH) with a 28S rDNA probe localized rDNA genes on one telomere of each X chromosome; these are the only brightly fluorescent C-positive regions revealed after CMA(3) staining, whereas all other heterochromatic bands are DAPI positive.