Del Toro-De Leon, G. | Search bioRxiv

bioRxiv2025

Maternal control of RNA decay safeguards embryo development

As in mammals, the plant embryo is surrounded by maternal tissues that provide protection from the external environment. In angiosperms, a double fertilization process results in the formation of a diploid embryo and a triploid endosperm, both of which develop within maternal sporophytic integuments. Thus, the seed of angiosperms is a combined structure of three genetically distinct components: embryo, endosperm, and maternal integuments. It has long been assumed that the maternal plant influences embryo development, but there is limited molecular evidence for a direct pathway through which the maternal sporophyte aYects embryogenesis. Here we show that secondary small interfering RNAs (siRNAs) generated upon exosome impairment lead to embryo abortion through a maternal sporophytic eYect. Depletion of the core subunit of the RNA-processing exosome RRP45B (CER7) causes globular embryo arrest connected to ectopic post-transcriptional gene silencing (PTGS). Seed coat expression of CER7 suppresses seed abortion, demonstrating a maternal sporophytic control of embryo development through an RNA decay safeguard pathway. Our data support a model in which a primary siRNA trigger originates in the maternal integuments of the cer7 seed coat and drives PTGS amplification in reproductive tissues after fertilization, ultimately leading to seed abortion. In addition, our genetic and molecular data suggest that overloading of AGO1 with siRNAs impairs miRNA function, likely leading to embryo arrest. Our data highlight the complex interplay between maternal and embryonic gene regulation, reinforcing the importance of controlled RNA decay in plant development.

plant biology↗

bioRxiv2020

Maternal genome dominance in early plant embryogenesis

Previous studies have alternately supported and discounted the hypothesis that the maternal genome plays a predominant role in early embryogenesis in plants. We used 24 embryo defective (emb) mutants of Arabidopsis thaliana to test for maternal and paternal effects in early embryogenesis. 5 emb mutants had equal maternal and paternal effects, 5 showed maternal effects and weak paternal effects, and the remaining 14 emb mutants conditioned only maternal effects, demonstrating a more important role for the maternal allele for most of these EMB genes. To assess genome-wide maternal and paternal contributions to early embryos, we produced allele-specific transcriptomes from zygote to mature stage embryos derived from reciprocal crosses of Columbia-0 and Tsu-1, a hybrid combination we show to be a faithful proxy for isogenic Columbia-0. Parent-of-origin analysis of these transcriptomes revealed a reciprocal maternal bias in thousands of genes from the zygote to octant stage. This bias greatly diminished by the globular stage, and was absent at later stages. Comparison with egg cell transcriptomes revealed no correlation between transcript levels in the egg and maternal bias in pre-globular embryos, suggesting that the maternal bias observed in early embryos is due to preferential zygotic transcription of maternal alleles. Taken together, the functional and transcriptome data presented here support a predominant role for the maternal genome in early Arabidopsis embryogenesis. SignificanceIn both animals and plants, the zygote is produced by the union of the egg and sperm cells. In animals, it is well accepted that mRNAs and proteins from the egg direct the first steps of embryogenesis. Here we present genetic and genomic experiments that support a predominant role for the maternal genome in early embryogenesis of plants, as well. In contrast to animals, our data suggest that this maternal influence is primarily derived not from inheritance of egg transcripts, but from preferential transcription of maternal alleles in the zygote and early embryo. This transient maternal zygotic bias may reflect an ancestral condition to diminish paternal influence on early embryogenesis in outcrossing plants.

plant biology↗