Cytoplasmic male sterility and mitochondrial metabolism in plants

• CMS is caused by a mitochondrial sterilizing factor.
• The link between sterilizing factor and pollen abortion remains unknown.
• The ATP hypothesis suggests that reduced mtATP production is causing male sterility.
• Studies of respiratory mutants do not support the ATP hypothesis.

Cytoplasmic male sterility (CMS) is a common feature encountered in plant species. It is the result of a genomic conflict between the mitochondrial and the nuclear genomes. CMS is caused by mitochondrial encoded factors which can be counteracted by nuclear encoded factors restoring male fertility. Despite extensive work, the molecular mechanism of male sterility still remains unknown. Several studies have suggested the involvement of respiration on the disruption of pollen production through an energy deficiency. By comparing recent works on CMS and respiratory mutants, we suggest that the “ATP hypothesis” might not be as obvious as previously suggested.