Fig. 2.

Regulation of target genes by PRC2 in inter-specific hybrid endosperm. (A) Alteration of PRC2 regulation by quantitative difference. The PRC2 proteins MEA, FIS2, FIE and MSI1 form a complex and repress target genes. The balance of PRC2 and target genes is different between parental species. In hybrid endosperm between maternal species I and paternal species II, misexpression of target genes is observed because maternally imprinted genes, MEA and FIS2, are not expressed from paternal species II. (B) Alteration of PRC2 regulation by qualitative difference. Two types of PRC2 complex, functional PRC2 and chimera complex, formed in hybrid endosperm. Chimera complex is assembled from MEA and FIS2, which are expressed only when they are derived from maternal species I allele, and FIE and MSI1 from species II allele. Chimera complex may be adversely affected by the diversity of the amino acid sequence of the PRC2 component.