Similarity between soybean and Arabidopsis seed methylomes and loss of non-CG methylation does not affect seed development

Proc Natl Acad Sci U S A. 2017 Nov 7;114(45):E9730-E9739. doi: 10.1073/pnas.1716758114. Epub 2017 Oct 23.

Abstract

We profiled soybean and Arabidopsis methylomes from the globular stage through dormancy and germination to understand the role of methylation in seed formation. CHH methylation increases significantly during development throughout the entire seed, targets primarily transposable elements (TEs), is maintained during endoreduplication, and drops precipitously within the germinating seedling. By contrast, no significant global changes in CG- and CHG-context methylation occur during the same developmental period. An Arabidopsis ddcc mutant lacking CHH and CHG methylation does not affect seed development, germination, or major patterns of gene expression, implying that CHH and CHG methylation does not play a significant role in seed development or in regulating seed gene activity. By contrast, over 100 TEs are transcriptionally de-repressed in ddcc seeds, suggesting that the increase in CHH-context methylation may be a failsafe mechanism to reinforce transposon silencing. Many genes encoding important classes of seed proteins, such as storage proteins, oil biosynthesis enzymes, and transcription factors, reside in genomic regions devoid of methylation at any stage of seed development. Many other genes in these classes have similar methylation patterns, whether the genes are active or repressed. Our results suggest that methylation does not play a significant role in regulating large numbers of genes important for programming seed development in both soybean and Arabidopsis. We conclude that understanding the mechanisms controlling seed development will require determining how cis-regulatory elements and their cognate transcription factors are organized in genetic regulatory networks.

Keywords: Arabidopsis; DNA methylation; seed development; soybean; transposon.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Arabidopsis / genetics*
  • Base Sequence
  • DNA Methylation / genetics
  • DNA Methylation / physiology*
  • DNA Transposable Elements / genetics
  • DNA Transposable Elements / physiology
  • DNA, Plant / metabolism*
  • Gene Expression Profiling
  • Gene Expression Regulation, Plant / genetics
  • Gene Regulatory Networks
  • Gene Silencing
  • Genes, Plant / genetics
  • Genome, Plant / genetics
  • Germination / genetics
  • Plant Proteins / genetics
  • Plant Proteins / metabolism
  • RNA, Plant / genetics
  • RNA, Plant / metabolism
  • Seedlings / genetics
  • Seedlings / metabolism
  • Seeds / cytology
  • Seeds / genetics*
  • Seeds / growth & development*
  • Soybeans / genetics*

Substances

  • DNA Transposable Elements
  • DNA, Plant
  • Plant Proteins
  • RNA, Plant