Trisomic analysis of ribosomal RNA cistron multiplicity in barley (Hordeum vulgare L.) |
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| Authors: | N. C. Subrahmanyam A. A. Azad |
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| Affiliation: | (1) Genetics Department, Research School of Biological Sciences, The Australian National University, PO Box 475, 2601 Canberra City, A.C.T., Australia;(2) Molecular Biology Unit, Research School of Biological Sciences, The Australian National University, PO Box 475, 2601 Canberra City, A.C.T., Australia |
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| Abstract: | Ribosomal RNA cistron numbers in all the seven primary trisomics of diploid barley (Hordeum vulgare L.) were determined by DNA-rRNA filter hybridisation. Trisomies for the nucleolus organiser (NO) chromosomes 6 and 7 showed the highest levels of rDNA (DNA complementary to rRNA) indicating the localisation of rRNA cistrons on the NOs. Chromosomes 6 and 7 possessed 1,580 and 2,690 rRNA (18S + 5.8S + 26S) cistrons respectively. Trisomics for the other chromosomes (except for 3) also displayed levels of rDNA significantly higher (22–32%) than the diploid controls although the dosage of NOs was not altered. These non-specific increases were also present in trisomics for 6 and 7 (NOs) which showed further increases equivalent to their respective contributions. The nonspecific increases due to trisomy is indicative of rDNA compensation. Such increases did not persist in diploid sibs of the trisomics, demonstrating the nonheritable nature of the compensation. |
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