Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
2043544 | Current Biology | 2008 | 7 Pages |
SummaryUnlike animals that produce gametes upon differentiation of meiotic products, plants develop haploid male and female gametophytes that differentiate gametes such as sperm, egg and central cells, and accessory cells 1 and 2. Both gametophytes participate in double fertilization and give rise to the next sporophytic generation. Little is known about the function of cell-cycle genes in differentiation and development of gametophytes and in reproduction 1 and 2. RETINOBLASTOMA RELATED (RBR) is a plant homolog of the tumor suppressor Retinoblastoma (pRb), which is primarily known as negative regulator of the cell cycle [3]. We show that RBR is required for cell differentiation of male and female gametophytes in Arabidopsis and that loss of RBR perturbs expression levels of the evolutionarily ancient Polycomb Repressive Complex 2 (PRC2) subunits and their modifiers encoding PRC2 subunits or DNA METHYLTRANSFERASE 1 (MET1) 4, 5 and 6, exemplifying convergent evolution involving the RBR-PRC2-MET1 regulatory pathways. In addition, RBR binds MET1, and maintenance of heterochromatin in central cells, a mechanism that is likely mediated by MET1 7 and 8, is impaired in the absence of RBR. Surprisingly, PRC2-specific H3K27-trimethylation activity represses paternal RBR allele, suggesting a functional role for a dynamic and reciprocal RBR-PRC2 regulatory circuit in cellular differentiation and reproductive development.