Cytosine methylation and nucleolar dominance in cereal hybrids |
| |
Authors: | K Houchins M O'Dell R B Flavell and J P Gustafson |
| |
Institution: | (1) United States Department of Agriculture, Agricultural Research Service, Plant Genetics Research Unit, and Plant Science Unit, University of Missouri, Columbia, MO 65211, USA, US;(2) John Innes Centre, Norwich Research Park, Colney, Norwich, Norfolk NR4 7UH, UK, NF |
| |
Abstract: | In wheat-rye hybrids the nucleolus organizer regions (NORs), the sites of ribosomal RNA genes, from rye are suppressed. Wheat
and wheat-rye hybrid genetic stocks containing different numbers of wheat and rye nucleolus organizers, as well as addition
lines and rye-barley hybrids, were used in Southern hybridization experiments to determine the cause of nucleolar dominance
and suppression in cereal hybrids. Based on the use of restriction endonucleases that cleave near the ends of the spacer unit
and an additional, methylation-sensitive enzyme, HpaII, which does not recognize the CCGG restriction site if the internal C is methylated, an indirect method of assaying NOR
expression was established. The results indicated that cleavage by the HpaII enzyme of the rye NOR sequences, is reduced when major NORs from other cereals were present. The reduction in the number
of rye rRNA genes containing an unmethylated CCGG site in the promoter was associated with the suppression of the rye nucleolus.
These results are consistent with a model in which promoter and upstream regulatory repeats of ribosomal RNA genes compete
for limited concentrations of regulatory proteins, and genes that are methylated at key binding sites fail to engage these
regulatory proteins and thus remain inactive.
Received: 15 November 1996 / Accepted: 19 March 1997 |
| |
Keywords: | Nucleolar dominance Nucleolar organizer region Methylation |
本文献已被 SpringerLink 等数据库收录! |
|