Genetics, Vol 129, 727-734, Copyright © 1991


INVESTIGATIONS

Permanent Rescue of a Non-Mendelian Mutation of Paramecium by Microinjection of Specific DNA Sequences

H. Jessop-Murray, L. D. Martin, D. Gilley, J. R. Preer-Jr. and B. Polisky
Program in Molecular, Cellular, and Developmental Biology, Department of Biology, Indiana University, Bloomington, Indiana 47405

The mutant Paramecium tetraurelia cell line d48 is unable to express the serotype A protein on its surface. Although the A gene is intact in the micronuclei of d48, the A gene copies in the macronucleus contain a large deletion eliminating virtually the entire coding sequence. Previous studies showed that microinjection of a plasmid containing the entire A gene into the macronucleus of d48 permanently restored A expression after autogamy. Together with other data, this result suggests that in wild type cells the A gene in the old macronucleus ensures the presence of a cytoplasmic factor that prevents A gene deletions at autogamy. In d48, where there are few, if any copies of the intact A gene in the old macronucleus, deletions occur during macronuclear formation. To elucidate the specific molecular mechanisms involved in this unusual phenomenon, we attempted to define the region(s) of the A gene necessary for rescuing d48. We show that microinjection of a 4.5-kb internal A gene fragment is sufficient for proper processing at autogamy and leads to permanent rescue of d48; i.e., the rescued strain is indistinguishable from wild type. Thus, rescue of d48 does not require upstream transcriptional control sequences, intact A mRNA or A serotype protein. We also show that various fragments of the A gene have the ability to rescue d48 to different extents, some being more efficient than others. We find no evidence to suggest that the A gene gives rise to a small stable RNA that might act as or encode a cytoplasmic factor. Molecular mechanisms that may be involved in the rescue of d48 are discussed.


This article has been cited by other articles:


Home page
GeneticsHome page
A. Matsuda and M. Takahashi
Non-Mendelian Inheritance Induced by Gene Amplification in the Germ Nucleus of Paramecium tetraurelia
Genetics, January 1, 2005; 169(1): 137 - 147.
[Abstract] [Full Text] [PDF]


Home page
Mol. Cell. Biol.Home page
O. Garnier, V. Serrano, S. Duharcourt, and E. Meyer
RNA-Mediated Programming of Developmental Genome Rearrangements in Paramecium tetraurelia
Mol. Cell. Biol., September 1, 2004; 24(17): 7370 - 7379.
[Abstract] [Full Text] [PDF]