Genomic imprinting is believed to be an inherently epigenetic phenomenon in which differential allele expression occurs in a parent-of-origin dependent manner. In plants, imprinting is mainly observed in the endosperm, an organ specialized to supply nutrients to the developing angiosperm embryo. The major causes of genomic imprinting are changes to gene accessibility resulting from DNA methylation and/or alteration of the chromatin structure. The major targets of these epigenetic marks are insertions of transposable elements (TEs), sequences of DNA with the ability to move from one locus in the genome to another when they are active. In this study, we wanted to explore the relationship between imprinted genes and TE insertions. We hypothesized that the introduction of silenced Mutator (Mu) transposons near or within genes would cause the differential expression of the maternal and paternal alleles of the genes, and thus create novel imprinted genes in maize endosperm. . To test our hypothesis, we performed a reciprocal cross of a Mu silenced line in the B73 background with a Mo17 inbred line, deep RNAseq to detect the allele specific expression values of genes, and Miseq to profile Mu insertions for endosperm samples collected 14 days after pollination. We detected 564 maternally expressed genes (MEGs) and 143 paternally expressed genes (PEGs) showing moderate or strong allele biased expression from the expected 2m:1p ratio. In addition, we identified 272 Mu insertions, 78.4% of which were in or within 1 kb of a gene body. Of these, four were able to generate novel PEGs and eleven of these were able to generate novel MEGs. These findings point to the importance of TEs in generating novel gene expression patterns in maize endosperm.
Authors: Claire Stoll
Faculty Advisors: Drs. Meixia Zhao and Diya Yang, Department of Biology
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