For both plants and animals, the transition of a fertilized egg cell into a zygote is a critical step in sexual reproduction. In animals, early embryonic divisions rely on maternally provided gene products. Using a rice model, zygotic genome activation in plants is shown to occur before the first embryonic division. Transcription factors expressed by the paternal genome trigger the zygotic transition. The maternal alleles are silenced, thereby imposing a fertilization requirement for embryogenesis. Manipulation of the corresponding genes in eggs bypasses fertilization, resulting in parthenogenesis. When combined with editing of meiosis genes, plants that reproduce stably as genetic clones can be generated. With these gene alterations, hybrid rice propagated through seeds maintains uniform hybrid vigour in subsequent generations. Fixation of hybrid vigour in crop plants has broad implications for the availability of high-yielding hybrid seeds at low cost to subsistence farmers.
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