Chromosome painting of Y chromosomes and isolation of a Y chromosome-specific repetitive sequence in the dioecious plant Rumex acetosa

The dioecious plant Rumex acetosa has a multiple sex chromosome system: XX in female and XY1Y2 in male. Both types of Y chromosome were isolated from chromosome spreads of males by manual microdissection, and their chromosoma l DNA was amplified using degenerate oligonucleotide primed-polymerase chai n reaction (DOP-PCR). When the biotin-labeled DOP-PCR product was hybridize d with competitor DNA in situ, the fluorescent signal painted the Y chromos omes. A library of Y chromosome DNA was constructed from the DOP-PCR produc t and screened for DNA sequences specific to the Y chromosome. One Y chromo some-specific DNA sequence was identified and designated RAYSI (R. acetosa Y chromosome-specific sequence I). RAYSI is a tandemly arranged repetitive DNA sequence that maps to the 4',6-diamidino-2-phenylindole bands of both Y chromosomes.