CMS

Sandhu APS, Abdelnoor RV & Mackenzie SA 2007 Transgenic induction of mitochondrial rearrangements for cytoplasmic male sterility in crop plants. PNAS 104:1766-1770.

• CMS mutations might not arise de novo in a mitochondrial population at the time male sterility occurs, but rather may already be present at low copy number before their specific amplification

• substoichiometric mitochondrial DNA forms can be up- or down-regulated in relative copy number within one plant generation
• a process termed substoichiometric shifting (SSS)

• a nuclear gene in Arabidopsis was cloned that directly influences mitochondrial SSS
• the gene, designated Msh1, encodes a homolog of the Escherichia coli mismatch repair component MutS at its N terminus and contains a carboxyl-terminal domain homolog of a GIY-YIG-type homing endonuclease essential to MSH1 function

• experiments were designed to test the hypotheses that substoichiometric DNA forms within the mitochondrial genome can be selectively amplified by disruption of Msh1 expression, and that this selective amplification can give rise to CMS

• observation suggests that multiple generations are needed to complete the cytoplasmic sorting required to shift the mitochondrial DNA population to the altered configuration