Natural epigenetic polymorphisms lead to intraspecific variation in Arabidopsis gene imprinting: allele specific mRNA-seq expression profiling in Arabidopsis thaliana Col, Ler, and Cvi parental and reciprocal F1 hybrid embryo and endosperm

Imprinted gene expression occurs during seed development in plants and is closely tied to differential DNA methylation of maternal and paternal alleles, particularly at proximal transposable elements (TEs). Since the epigenetic modification of TEs can vary within species, we investigated intraspecific variation in imprinting, coupled with analysis of DNA methylation and small RNAs, among three strains of Arabidopsis that display diverse seed size phenotypes. Unexpectedly we found that one strain, Cvi, is globally CG hypomethylated. We discovered three examples of strain-specific imprinting caused by epigenetic variation at a TE. Our data allowed us to predict and experimentally validate an instances of allele-specific imprinting in additional strains based only on methylation patterns. We conclude that numerous differences in imprinting can evolve in highly similar, recently diverged genotypes due to epiallelic variation present within the species. Our data demonstrate that epiallelic variation and genomic imprinting intersect to produce novel gene expression patterns in seeds. Examination of parent-of-origin specific and total gene expression in embryo, endosperm, and whole seeds. Samples with the same heading are biological replicates (e.g. CVN1, CVN2, and CVN3). High throughput Illumina sequencing of poly-A selected RNA from Arabidopsis Col, Ler and Cvi reciprocal F1 hybrid embryo and endosperm tissue isolated at 6 days after pollination to identify imprinted genes.