A Small RNA Pathway Mediates Allelic Dosage in Endosperm

Cell Rep. 2017 Dec 19;21(12):3364-3372. doi: 10.1016/j.celrep.2017.11.078.

Abstract

Balance between maternal and paternal genomes within the triploid endosperm is necessary for normal seed development. The majority of endosperm genes are expressed in a 2:1 maternal:paternal ratio, reflecting genomic DNA content. Here, we find that the 2:1 transcriptional ratio is, unexpectedly, actively regulated. In A. thaliana and A. lyrata, endosperm 24-nt small RNAs are reduced in transposable elements and enriched in genes compared with the embryo. We find an inverse relationship between the parent of origin of sRNAs and mRNAs, with genes more likely to be associated with maternally than paternally biased sRNAs. Disruption of the Pol IV sRNA pathway causes a shift toward maternal allele mRNA expression for many genes. Furthermore, paternal inheritance of an RNA Pol IV mutation is sufficient to rescue seed abortion caused by excess paternal genome dosage. Thus, RNA Pol IV mediates the transcriptional balance between maternally and paternally inherited genomes in endosperm.

Keywords: A. lyrata; A. thaliana; DNA methylation; RNA Pol IV; dosage; endosperm; imprinting; small RNA.

MeSH terms

  • Alleles
  • Arabidopsis
  • DNA Transposable Elements
  • DNA-Directed RNA Polymerases / genetics
  • Endosperm / genetics*
  • Gene Dosage*
  • Maternal Inheritance
  • MicroRNAs / genetics*
  • Paternal Inheritance
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism

Substances

  • DNA Transposable Elements
  • MicroRNAs
  • RNA, Messenger
  • RNA polymerase IV, Arabidopsis
  • DNA-Directed RNA Polymerases