Genomic imprinting in plants

Flickin’ the ubiquitin switch

“…47 PHE1 is an example of paternal imprinting in Arabidopsis; the maternal allele is silenced by the FIS complex (the plant equivalent of the fly Polycomb Group complex) prior to fertilization, through tri-methylation of H3K27. 54 Luo et al 47 thus suggested that deubiquitylation of H2B by UBP26 may be a prerequisite for such H3K27 tri-methylation, in agreement with the finding that RNAi depletion of the H2B ubiquitin protease USP7 in fly S2 cell culture results in a global decrease of H3K27me3. 38,47 The disparate effects of UBP26 in two different genetic backgrounds (being required for either FLC transcription or PHE1 repression) hint at complex, gene differential effects and emphasize the redundancy of H2B ubiquitin proteases in higher eukaryotes, highlighting a need to confirm findings in reduced systems.…”

Regulation and Flexibility of Genomic Imprinting during Seed Development

“…Alternative theories have been proposed to explain the evolution of genomic imprinting and are reviewed elsewhere (Garnier et al, 2008;Moore and Mills, 2008). One of these proposes that genomic imprinting evolved to prevent parthenogenesis, explaining why gynogenotes and androgenotes fail to complete development McGrath and Solter, 1984;Surani et al, 1984;Solter, 1988;Varmuza and Mann, 1994).…”

Pol IV-Dependent siRNAs in Plants

“…It is, therefore, more plausible that p4-siRNA imprinting occurs in parallel with imprinting of protein-coding genes (Mosher 2010). Because many imprinted genes affect growth and development of the endosperm and embryo, evolution of genomic imprinting is believed to arise from parental conflict over allocation of scarce maternal resources among half-sibling progeny (Garnier et al 2008). Whether the Pol IV/V pathway has a subtle affect on seed development is yet to be determined.…”

“…Interestingly, p4-siRNA expression is also imprinted, with accumulation in the endosperm occurring specifically from maternal chromosomes (Mosher et al 2009). In Arabidopsis, demethylation of maternal alleles by DME glycosylase/demethylase is required for correct expression of both paternally and maternally expressed imprinted genes (Garnier et al 2008). Recent genome-wide methylation profiling of endosperm demonstrates that p4-siRNA-producing loci are also maternally demethylated by DME (Gehring et al 2009;Hsieh et al 2009).…”

“…Genomic imprinting occurs only in placental mammals and flowering plants, where it is primarily restricted to the developing endosperm (Garnier et al 2008). Binary genomic imprinting, where one parent's allele is completely silent, is a rare expression pattern known to occur at 11 genes in Arabidopsis, with an estimated 50 genes imprinted genome-wide (Gehring et al 2006;Fitz Gerald et al 2009).…”