Possible roles for polycomb repressive complex 2 in cereal endosperm

Abstract

The polycomb repressive complex 2 (PRC2) is an evolutionarily conserved multimeric protein complex in both plants and animals. In contrast to animals, plants have evolved a range of different components of PRC2 and form diverse complexes that act in the control of key regulatory genes at many stages of development during the life cycle. A number of studies, particularly in the model species Arabidopsis thaliana, have highlighted the role of PRC2 and of epigenetic controls via parent-of-origin specific gene expression for endosperm development. However, recent research in cereal plants has revealed that although some components of PRC2 show evolutionary conservation with respect to parent-of-origin specific gene expression patterns, the identity of the imprinted genes encoding PRC2 components is not conserved. This disparity may reflect the facts that cereal plant genomes have undergone different patterns of duplication during evolution compared to A. thaliana and that the endosperm development program is not identical in monocots and eudicots. In this context, we focus this review on the expression of imprinted PRC2 genes and their roles in endosperm development in cereals.

Keywords: cereal plants; endosperm; epigenetics; imprinting; polycomb.

FIGURE 1

Polycomb repressive complex 2 (PRC2) components of OsFIE1 and OsFIE2 may have distinct roles in rice endosperm. Based on recent findings, PRC2 complexes that contain OsFIE1 and OsFIE2 are likely to have distinct roles. In the endosperm, the OsFIE1 protein is produced from the maternally derived allele and contributes to the FIE1-containing PRC2 (left), By contrast, OsFIE2 protein derived from both maternal and paternal alleles is used to form FIE2-containing PRC2 (right).