Maternal and paternal genomes contribute equally to the transcriptome of early plant embryos

Transcriptome sequencing and analysis of hybrid embryos show that in contrast to early animal embryogenesis, early plant embryogenesis is mostly under zygotic control. Parental influence in plant embryos Maternally derived gene products control embryonic development before the activation of the zygotic genome in animals. The textbook view is that much the same happens in plants, yet this seems to conflict with some genetic and gene-expression results. Using transcriptome sequencing and analysis from carefully constructed hybrid embryos, Michael Nodine and David Bartel show that, in the model plant Arabidopsis thaliana , early embryogenesis is mostly under zygotic control, with both parental genomes making essentially equal contributions to the zygotic transcriptome. In animals, maternal gene products deposited into eggs regulate embryonic development before activation of the zygotic genome 1 . In plants, an analogous period of prolonged maternal control over embryogenesis is thought to occur based on some gene-expression studies 2 , 3 , 4 , 5 , 6 . However, other gene-expression studies and genetic analyses show that some transcripts must derive from the early zygotic genome 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , implying that the prevailing model does not fully explain the nature of zygotic genome activation in plants. To determine the maternal, paternal and zygotic contributions to the early embryonic transcriptome, we sequenced the transcripts of hybrid embryos from crosses between two polymorphic inbred lines of Arabidopsis thaliana and used single-nucleotide polymorphisms diagnostic of each parental line to quantify parental contributions. Although some transcripts seemed to be either inherited from primarily one parent or transcribed from imprinted loci, the vast majority of transcripts were produced in near-equal amounts from both maternal and paternal alleles, even during the initial stages of embryogenesis. Results of reporter experiments and analyses of transcripts from genes that are not expressed in sperm and egg indicate early and widespread zygotic transcription. Thus, in contrast to early animal embryogenesis, early plant embryogenesis is mostly under zygotic control.