ORIGINAL PAPER

Molecular and General Genetics MGG

, Volume 257, Issue 2, pp 177-185

First online:

Low-copy-number molecules are produced by recombination, actively maintained and can be amplified in the mitochondrial genome of Brassicaceae: relationship to reversion of the male sterile phenotype in some cybrids

  • M. BellaouiAffiliated withStation de Génétique et d'Amélioration des Plantes, INRA, Route de Saint-Cyr, 78026 Versailles Cedex, France Fax: 33-1-3083-3319; e-mail: budar@versailles.inra.fr
  • , A. Martin-CanadellAffiliated withStation de Génétique et d'Amélioration des Plantes, INRA, Route de Saint-Cyr, 78026 Versailles Cedex, France Fax: 33-1-3083-3319; e-mail: budar@versailles.inra.fr
  • , G. PelletierAffiliated withStation de Génétique et d'Amélioration des Plantes, INRA, Route de Saint-Cyr, 78026 Versailles Cedex, France Fax: 33-1-3083-3319; e-mail: budar@versailles.inra.fr
  • , F. BudarAffiliated withStation de Génétique et d'Amélioration des Plantes, INRA, Route de Saint-Cyr, 78026 Versailles Cedex, France Fax: 33-1-3083-3319; e-mail: budar@versailles.inra.fr

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Abstract

A PCR analysis of mitochondrial (mt) genomes of cybrid rapeseed plants revealed substoichiometric concentrations of molecules bearing different configurations of the gene (orf138) responsible for Ogura cytoplasmic male sterility (CMS). These sub-stoichiometric molecules are also present in plants bearing the unmodified Ogura cytoplasm. In one cybrid family, which shows reversion of the male sterile phenotype, we observed changes in the respective proportions of these molecules. The phenotypic (sterility-fertility) reversion occurs as a result of a modification of the equilibrium state between the different forms of the orf138 gene and is very probably determined by the level of expression of this gene. Stable situations are always characterized by one predominant form; the others, when present, exist in substoichiometric amounts. We report results indicating that the different forms of the orf138 gene are continuously interconverted by recombination and that an active mechanism is involved in the maintenance of some substoichiometric molecules.

Key words Mitochondrial genome Homologous recombination Substoichiometric molecules Cytoplasmic male sterility