Ruiyang Chen

Differentiating sex chromosomes of the dioecious Spinacia oleracea L. (spinach) by FISH of 45S rDNA

Spinacia oleracea L. (spinach) is a dioecious species with both male and female plants having 2n = 2x = 12 chromosomes, consisting of two large metacentrics, two long subtelocentrics, two short subtelocentrics, two acrocentrics, and four submetacentrics. The location of 45S rDNA was investigated on metaphase chromosomes using fluorescence in situ hybridization (FISH). The numbers of 45S rDNA foci in diploid sets of chromosomes from females was six and from males was five. All the fluorescent foci lay in secondary constrictions and the satellites. Our results indicate that an XY-type sex chromosome system could be present in spinach where the Y chromosome lacks a 45S RNA focus.

Characters of DNA constitution in the rye B chromosome.

We have used chromosome microdissection and microcloning to construct a DNA library of the entire B chromosome (B) of rye. New rye B-specific sequences have been screened from this pool, blasted with other sequences and analyzed to elucidate the characters of DNA constitution and the possible pathway of the origin of the rye B chromosome. We report the discovery of a new sequence that is specific to the rye B centromere.

Physical mapping of 45S rDNA to metaphase chromosomes in 30 taxonomically diverse plant species

Summary The genomic distribution of ribosomal RNA genes (rDNA) has been determined by fluorescence in situ hybridisation (FISH) in 30 diverse plant species, using 45S rDNA as a probe. In most species, physical mapping of 45S rDNA to metaphase chromosomes is reported for the first time. These species could be divided into four groups based on differences in the number and positions of their rDNA loci. Fluorescent signals lay in secondary constrictions and satellites of satellite-chromosomes (SAT-chromosomes) in 14 of the 30 species, including Berberis thunbergii, Plantago major, Sanicula lamelligera, Ficus carica and Robinia pseudoacacia. In another seven species, including Robinia hispida, Kolkwitzia amabilis, Litchi chinensis, Catalpa speciosa and Acer buergerianum, FISH markers were also detected in the terminal and/or peri-centromeric regions of some chromosomes beside secondary constrictions and satellites. There was only one species (Viburnum sargentii) in which four pairs of SAT-chromosomes were found, only one pair of which gave FISH signals. In the other eight species, including Kerria japonica f. pleniflora, Salvia miltiorrhiza, Cucumis sativus and Ulmus pumila, no visible satellites existed and the positions of 45S rDNA loci on the chromosomes were terminal or peri-centromeric. Our results indicate that 45S rDNA can be used to identify individual chromosomes. The polymorphism of 45S rDNA loci is also discussed in this paper.

Homologous analysis on centromeric region sequences of A and B chromosomes from rye by FISH

Four centromeric segments from 6 chromosomes (Bs) of rye have been microdissected and amplified by linker adapter PCR (LA-PCR). The PCR products ranged from 100 to 2 000 bp. Fluorescencein situ hybridization (FISH) experiment has been carried out using PCR products as the probe, which was labeled by DIG-11-dUTP. The result confirms that these PCR products from Bs centromeric region are homologous with that of A chromosomes (As) in rye. It also proves that Bs are originated from As.

Chromosome G-banding in plants by inducing with trypsin and urea *

Clear G-bands were revealed by applying the TUG method on chromosomes of 5 species of higher plants (Lilium davidii, Viciafaba, Hordeum vulgare, Ginkgo biloba and Triticum monococcum). Some details of the TUG method which consisted of treating chromosomes with both trypsin and urea were also studied. The mechanisms that might account for the presence of G-bands in plants were discussed.