Pollen abortion due to cytoplasmic factors that are maternally transmitted, but that act only in the absence of pollen-restoring genes. Such sterility can also be transmitted by grafting. In maize, pollen death is due to “abortion proteins” secreted by mitochondria, and the genes required to restore pollen fertility lower the abundance of abortion proteins by reducing rates of transcription of their mRNAs. Hybrid corn seed is produced commercially by a breeding system involving CMS. Unfortunately, the abortion proteins also enhance susceptibility of the plants to fungal toxins. See Chronology, 1987, Dewey, Timothy, and Levings, Bipolaris maydis, hybrid corn.
Subjects: Genetics and Genomics.