Parental contributions to the transcriptome of early plant embryos.

In plants and animals, embryo development becomes ultimately controlled by zygotic genes, but the timing of zygotic genome activation (ZGA) varies greatly between organisms. We recently showed that the transcriptome of young Arabidopsis embryos is dominated by maternal transcripts with a progressive ZGA under the maternal control of epigenetic pathways. In contrast, another study reported that both parental genomes contribute equally to the transcriptome of young embryos, suggesting that ZGA occurs immediately after fertilization. How to explain such dramatic differences? We propose that the discrepancies between these two studies likely reflect genuine biological differences between the two experiments, paving the road towards exciting discoveries on ZGA mechanisms in plants.