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Tzung-Fu Hsieh 한국육종학회 2013 한국육종학회 심포지엄 Vol.2013 No.07
The companion cells of the Arabidopsis thaliana egg and sperm, the central and vegetative cells, undergo active DNA demethylation prior to fertilization. However, its biological significance, extent of conservation, and targeting preferences are not yet clear. We recently showed that localized demethylation of interspersed, small transposable elements is a common feature of A. thaliana companion cells. The DEMETER DNA glycosylase encodes active DNA demethylase activity and is required for seed production. DME-mediated DNA demethylation in the central cell is required to establish imprinted gene expression in the endosperm, and is considered a master regulator for plant gene imprinting. However, the similarity among DME targets in the central and vegetative cells, despite their different functions and developmental fates, suggests that establishment of genomic imprinting may not be the basal function of DME. Lack of DEMETER in vegetative cells causes reduced methylation of transposons in sperm. Our observation suggests that the primary function of companion cell demethylation is to reinforce transposon silencing in plant gametes.
Heritable Epigenetic Variation and its Potential Applications for Crop Improvement
( Changqing Zhang ),( Tzung Fu Hsieh ) 한국육종학회 2013 Plant Breeding and Biotechnology Vol.1 No.4
Phenotypic variation within organisms is driven primarily by genetic diversity. However, there is a growing appreciation that epigenetic variation, resulting from a multitude of diverse chemical modifications to the DNA and chromatin, can have profound effects on phenotype. Heritable epigenetic marks persist through meiosis and can be stably transmitted to the next generation, resulting in transgenerational epigenetic inheritance. Importantly, when epigenetic changes occur near coding genes, affecting their transcriptional state, heritable epigenetic variation can result in heritable phenotypic variation. Large-scale interrogation of epigenome inheritance in Arabidopsis has revealed that spontaneous variation in DNA methylation occurs at a rate that is orders of magnitude greater than genetic mutation, indicating the key importance of epigenetic variation during evolution. Thus, there is a potential for epigenetics to play a role in crop improvement, including regulation of trans gene expression and creation of novel epialleles. Here, we review cases of naturally occurring and genetically induced epialleles, and discuss how the studies from two epigenetic populations are rapidly increasing our understanding of epigenetic diversity.