Sexual epigenetics: gender-specific methylation of a gene in the sex determining region of Populus balsamifera

Sci Rep. 2017 Mar 27;7:45388. doi: 10.1038/srep45388.

Abstract

Methylation has frequently been implicated in gender determination in plants. The recent discovery of the sex determining region (SDR) of balsam poplar, Populus balsamifera, pinpointed 13 genes with differentiated X and Y copies. We tested these genes for differential methylation using whole methylome sequencing of xylem tissue of multiple individuals grown under field conditions in two common gardens. The only SDR gene to show a marked pattern of gender-specific methylation is PbRR9, a member of the two component response regulator (type-A) gene family, involved in cytokinin signalling. It is an ortholog of Arabidopsis genes ARR16 and ARR17. The strongest patterns of differential methylation (mostly male-biased) are found in the putative promoter and the first intron. The 4th intron is strongly methylated in both sexes and the 5th intron is unmethylated in both sexes. Using a statistical learning algorithm we find that it is possible accurately to assign trees to gender using genome-wide methylation patterns alone. The strongest predictor is the region coincident with PbRR9, showing that this gene stands out against all genes in the genome in having the strongest sex-specific methylation pattern. We propose the hypothesis that PbRR9 has a direct, epigenetically mediated, role in poplar sex determination.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • DNA Methylation / genetics*
  • Epigenesis, Genetic / genetics*
  • Epigenomics / methods
  • Gene Expression Regulation, Plant / genetics
  • Genome, Plant / genetics
  • Populus / genetics*