Cytoplasmic Male Sterility and Fertility Restoration in Petunia

Abstract

Cytoplasmic male sterility (CMS) in Petunia is due to an aberrant chimeric mitochondrially encoded gene designated pcf. Despite the ubiquitous expression of pcf throughout CMS Petunia plants, the primary defect is the disruption of pollen development. Sporogenous and tapetal cells in anthers of CMS lines display abnormalities during meiosis, ultimately resulting in abortion of pollen. Petunia lines carrying the CMS cytoplasm can be restored to normal male fertility by the presence of a single copy of a dominant nuclear Restorer of Fertility (Rf ) gene. The Rf gene reduces the amount of the CMS-associated protein to near-undetectable levels. The Rf gene in Petunia is a member of the pentatricopeptide repeat-motif-containing gene family, a large nuclear gene family implicated in control of the expression of organellar genes. Fertility restoration in Petunia appears to involve interactions between the RF protein and pcf transcripts, perhaps affecting processing and/or translation.