Researchers Identify Cause of Seed Abortion and Role of RNA Pol IV Enzyme in Seed Development

In flowering plants, the embryo is surrounded by the endosperm, which facilitates transfer of nutrient between embryo and the mother. The endosperm is distinct as it contains only one copy of the father's genome and two copies of the mother's. This maternal to paternal ratio is remarkable because of its importance to seed viability and development. Seeds with extra genomes that alter this critical ratio undergo a process known as interploidy seed abortion due to defective endosperm development.

The enzyme RNA Pol IV is specific to plant genomes that generate small RNA molecules silencing gene expression from transposons and repetitive DNA, playing a major role in defending the genome against viruses and transposable elements. A study published in Plant Cell shows that RNA Pol IV plays a key role in interploidy seed abortion.

The study shows that RNA Pol IV targets genes in the father through the "canonical" RNA-directed DNA methylation pathway. This results in interploidy seed abortion. The researchers then compared gene transcription in the endosperm of aborted interploidy seeds with seeds that were viable due to the loss of paternal RNA Pol IV. They found that transposons and thousands of genes, even imprinted ones, were misregulated in both living and dying seeds and learned that misregulation of a relatively small number of genes sets living seeds apart from aborting ones.

Read more details in the paper's abstract available in Plant Cell.