rDNA sites in mitotic and polytene chromosomes of Vigna unguiculata (L.) Walp. and Phaseolus coccineus L. revealed by in situ hybridization
1996
Guerra, M. | Kenton, A. | Bennett, M.D.
Root tip mitotic and tapetal polytene cells of Vigna unguiculata and Phaseolus coccineus were hybridized with a ribosomal DNA (rDNA) probe. While the number of rDNA sites were as expected for P. coccineus, it was surprisingly higher in V. unguiculata where ten rDNA sites were found in both tissues. A sequential banding technique on mitotic chromosomes of V. unguiculata was used to map the positions of the rDNA sites more accurately. In mitotic cells eight of the rDNA hybridization sites were similar in size while the remaining sites were smaller. In contrast, the hybridization sites were more variable in size in polytene cells with no more than six sites being relatively large. The differences in size of the hybridization sites between the two tissues suggest differential amplification of the rDNA sequences. In P. coccineus six hybridization sites were found in both tissue types. The relative sizes of the sites were similar in both tissue. The presence of speckled signal surrounding four of the six sites suggested that at least four of the rDNA sites were transcribed.
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