Activation of Silent Transposable Elements
It is well known among maize geneticists that agents that cause chromosome breakage can activate quiescent transposable elements. However, other than temporarily relieving position effect, it is difficult to understand how these events can lead directly to activation. One possibility is that chromosome breakage can initiate a process in the cell resulting in a higher rate of spontaneous mutation. Such a system could be analogous to the SOS response of Escherichia coli in which an error-prone repair system is induced. Chemical mutagens that cause little chromosome breakage but add bulky adducts to the DNA can induce the SOS response. In seed homozygous for a1-m2(8004), wx-m8, no active Spm, that had been treated with ethyl methanesulfonate, we observed activation of Spm at the rate of 1.1 × 10−4. The spontaneous rate of activation in this material was 1.2 × 10−5. Most of the activation events occurred as single kernels. This result contrasts with sectors covering at least one-eighth of the ear that would have been expected if activation had occurred as a direct result of mutagenesis in the mature kernel. The late timing of these events suggests that the activation, in most instances, may not be the direct result of chemical mutagenesis.
KeywordsMaize Ethyl Manifold Lymphoma Germinal
Unable to display preview. Download preview PDF.
- 4.Bianchi, A., F. Salamini, and R. Parlavecchio (1969) On the origin of controlling elements in maize. Genetica Agraria 22:335–344.Google Scholar
- 11.Coe, E.H., and M.G. Neuffer (1978) Embryo cells and their destinies in the corn plant. In The Clonal Basis of Development, S. Subtelny and I. Sussex, eds. Academic Press, New York, pp. 113–129.Google Scholar
- 14.Elespuru, R.K. (1984) Induction of bacteriophage lambda by DNA-interacting chemicals. Chem. Mutagens 9:213–231.Google Scholar
- 19.McClintock, B. (1951) Mutable loci in maize. Carnegie Institution Washington Yearbook 50:174–181.Google Scholar
- 20.McClintock, B. (1965) The control of gene action in maize. Brookhaven Symposia on Quantitative Biology 18:162–182.Google Scholar
- 21.McClintock, B. (1967) Genetic systems regulating gene expression during development. Develop. Biol. Suppl. 1:84–112.Google Scholar
- 22.McClintock, B. (1968) The states of a gene locus in maize. Carnegie Institution Washington Yearbook 66:20–28.Google Scholar
- 27.Neuffer, M.G., and E.H. Coe (1977) Paraffin oil technique for treating corn pollen with chemical mutagens. Maydica 22:21–28.Google Scholar
- 36.Spofford, J.B. (1976) Position-effect variegation in Drosophila. In The Genetics and Biology of Drosophila, M. Ashburner and E. Novitski, eds. Academic Press, New York, 1c:955–1018.Google Scholar