Retinoblastoma-related proteins in plants: homologues or orthologues of their metazoan counterparts?

The mammalian retinoblastoma tumor suppressor protein (pRb) regulates cell division, differentiation and apoptotic pathways in specific cell types. In association with other proteins, pRb acts in part by modulating transcript ional activity. Elements of the pRb regulatory network have been identified in higher plants. Recent findings involving these proteins, which display amino acid sequence homology and biochemical binding properties analogous t o their mammalian counterparts, are discussed.