Organization and expression of the mitochondrial genome in cytoplasmic revertants ofcms-S maize
Leja, Carol Ann
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Permalink
https://hdl.handle.net/2142/20815
Description
Title
Organization and expression of the mitochondrial genome in cytoplasmic revertants ofcms-S maize
Author(s)
Leja, Carol Ann
Issue Date
1991
Doctoral Committee Chair(s)
Laughnan, John R.
Department of Study
Biology
Discipline
Biology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Molecular
Language
eng
Abstract
The loss of $\sigma\sp\prime$ and $\psi\sp\prime$ termini of linear molecules was found to be a general characteristic of cytoplasmic reversion for all the nuclear-cytoplasmic genomic backgrounds examined in cms-S maize. Those cytoplasmic revertants that lose S1 and S2 lose $\sigma\sp\prime$ and $\psi\sp\prime$ termini by recombination with $\sigma$ and $\psi$ regions of the main mitochondrial genome to generate internal junction sequences of $\sigma$-$\sigma\sp\prime$, $\psi$-$\sigma\sp\prime$, $\sigma$-$\psi\sp\prime$, and $\psi$-$\psi\sp\prime$, thereby circularizing the mitochondrial genome. However, which internal junction sequences are generated appear to be influenced by the nuclear genotype. Cytoplasmic revertants that retain S1 and S2, namely those in the WF9 nuclear background, differ in the organization of their mitochondrial genome from those cytoplasmic revertants that lose S1 and S2. Although some data provide evidence for the loss of $\sigma\sp\prime$ and $\psi\sp\prime$ termini by recombination with $\psi$ in these revertants, the continued presence of termini of linear molecules having $\sigma$/$\psi$ adjacent to a terminal S1/S2 and the presence of altered $\sigma\sp\prime$/$\psi\sp\prime$ termini suggest that circularization of the mitochondrial genome does not accompany cytoplasmic reversion in the WF9 nuclear background. Since S1 and S2 continue to be present after cytoplasmic reversion in the WF9 nuclear background, loss or mutation of $\sigma\sp\prime$ and $\psi\sp\prime$ termini and of $\sigma$-R and $\psi$-R junctions may be a way to stabilize the organization of the mitochondrial genome as linear molecules. The 2 kb sequence common to $\sigma\sp\prime$ and $\psi\sp\prime$ appears to result in the production of sterile-specific transcripts.
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