Figure 7
GISH of American and Chinese chestnuts F1 hybrid. Early metaphase chromosome spread of an F1 (Chinese chestnut × American chestnut) GISH-ed with Chinese chestnut total genomic DNA as probe and American chestnut as blocking DNA along with the 35S rDNA probe to study structural and organizational differences between the species in a common background; (a) scattered green signals (Chinese chestnut DNA) show across all 24 chromosomes; the mj-35S rDNA bearing chromosome of American chestnut marked as ‘AC’ (diagrammatic sketch shown in top-right insert), and the mj-35S rDNA bearing chromosome of Chinese chestnut marked as ‘CC’ (diagrammatic sketch shown in bottom-right inset). An enlarged image of the Chinese chestnut satellite shown in upper-left insert; a complete genomic hybridization (green signal) can be seen clearly in the heterochromatic region (distal half) and the proximal half, which hybridized with the 35S rDNA are separated by a dotted line (marked by arrowheads); further the DAPI stained heterochromatic region and the red signal from the 35S rDNA blended together through the green signal as diffused blue-greenish and yellowish signals, respectively. The mn-35S rDNA bearing chromosomes marked by arrowheads. (b) The individual mj-35S rDNA bearing chromosome of each species with NOR (marked by brace, b3 and b7, respectively) under different filters: (b1–4) (Chinese chestnut chromosome; b1–b4 are images of red–green–blue, green–blue, red–blue filters, and blue filter, respectively; (b5–b8) (American chestnut chromosome, same set of filters applied as for Chinese chestnut). (b4) The proximal region of the Chinese chestnut satellite and the distal region of the short arm shown in dotted boxes 1 and 2, respectively; the secondary constriction (SC, brace) which does not seem to stain with DAPI (i.e., DAPI negative). (b8) The distal part of the short arm of American chestnut shown in a dotted box, and its secondary constriction (SC, brace) also appears not to be stained with DAPI. Chinese chestnut satellite under red-green filters (without blue filter, i.e., DAPI) is given in the lower-bottom insert in ‘b1’. Bar = 5 µm.
