The AT-rich regions correspond to the localized centromeres in meiotic chromosomes of <i>Drosera filiformis</i> Raf.

To investigate the mitotic and meiotic chromosome behaviors of the polyploid Drosera group, D. filiformis and D. rotundifolia were observed using orcein staining and DNA base-specific fluorescence staining with two counterstaining fluorochromes: GC-specific chromomycin A3 (CMA) and AT-specific 4′,6-diamidino-2-phenylindole (DAPI). Both species exhibited 2n=20 and n=10II. No clear primary constrictions were observed in the mitotic metaphase chromosomes of either species. At mitotic anaphase, sister chromatids of each chromosome separated parallel to each other, exhibiting uniform separation in both species. In the DNA base-specific staining, two CMA-positive and DAPI-negative (CMA+DAPI−) satellites were observed at one end of two chromosomes in D. filiformis, whereas no obvious satellites were detected in D. rotundifolia except in one strain. A single CMA−DAPI+ band was observed on each of the 20 chromosomes in D. filiformis, while no CMA−DAPI+ bands were observed in D. rotundifolia. In meiosis, each bivalent in both species clearly exhibited a localized centromere at metaphase of the first meiotic division (metaphase I). However, the bivalent morphologies of the centromeric regions during chromosome segregation at metaphase I differed markedly between the two species: The centromeres of D. filiformis were spherical shape with CMA−DAPI+ bands, while the centromeres of D. rotundifolia were needlelike shape and lacked any fluorescence bands.