Retinoblastoma protein regulates cell proliferation, differentiation, and endoreduplication in plants

• Published in: The Plant journal : for cell and molecular biology 2005-04, Vol.42 (2), p.153-163
• Main Authors: Park, J.A, Ahn, J.W, Kim, Y.K, Kim, S.J, Kim, J.K, Kim, W.T, Pai, H.S
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Botany; cell cycle; cell differentiation; Cell Differentiation - physiology; Cell division; Cell kinetics; Cell physiology; Cell Proliferation; Chemical agents; complementary DNA; cytology; E2F; E2F transcription factor; elevated cell proliferation; endoreduplication; epidermis (plant); Flowers & plants; Fundamental and applied biological sciences. Psychology; gene expression regulation; Gene Expression Regulation, Plant; Gene Expression Regulation, Plant - physiology; Gene Silencing; Genes; Nicotiana - cytology; Nicotiana - physiology; Nicotiana benthamiana; Nicotiana tabacum; physiology; Plant Leaves; Plant Leaves - physiology; Plant Leaves - ultrastructure; plant morphology; Plant physiology and development; plant proteins; Plant Proteins - physiology; Plant Stems; Plant Stems - physiology; Plants, Genetically Modified; Retinoblastoma Protein; Retinoblastoma Protein - physiology; retinoblastoma-related protein 1; stomata; stomatal clusters; S‐phase genes; Tobacco; transcription (genetics); transcription factors; Transcription, Genetic; trichomes; ultrastructure; Up-Regulation; Vegetative apparatus, growth and morphogenesis. Senescence; virus-induced gene silencing
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/j.1365-313x.2005.02361.x

Retinoblastoma protein (Rb) plays a key role in cell cycle control, cell differentiation, and apoptosis in animals. In this study, we used virus-induced gene silencing (VIGS) to investigate the cellular functions of Rb in higher plants. VIGS of NbRBR1, which encodes the Nicotiana benthamiana Rb homolog, resulted in growth retardation and abnormal organ development. At the cellular level, Rb suppression caused prolonged cell proliferation in tissues that are normally differentiated, which indicates that Rb is a negative regulator of plant cell division. Furthermore, differentiation of the epidermal pavement cells and trichomes was partially retarded, and stomatal clusters formed in the epidermis, likely due to uncontrolled cell division of stomata precursor cells. Rb suppression also caused extra DNA replication in endoreduplicating leaf cells, suggesting a role of Rb in the endocycle. These Rb phenotypes were accompanied by stimulated transcription of E2F and E2F-regulated S-phase genes. Thus, disruption of Rb function in plants leads to ectopic cell division in major organs that correlates with a delay in cell differentiation as well as increased endoreduplication, which indicates that Rb coordinates these processes in plant organ development.