The plant cell cycle--15 years on.
The basic components of the plant cell cycle are G1 (postmitotic interphase), S-phase (DNA synthesis phase), G2 (premitotic interphase) and mitosis/cytokinesis. Proliferating cells are phosphoregulated by cyclin-dependent protein kinases (CDKs). Plant D-type cyclins are sensors of the G0 to G1 transition, and are also important for G2/M. At G1/S, the S-phase transcription factor, E2F, is released from inhibitory retinoblastoma protein. Negative regulation of G1 events is through KRPs (Kip-related proteins). Plant S-phase genes are similar to animal ones, but timing of expression can be different (e.g. CDC6 at the start of S-phase) and functional evidence is limited. At G2/M, A-type and the unique B-type CDKs when bound to A, B and D cyclins, drive cells into division; they are negatively regulated by ICK1/2 and perhaps also by WEE1 kinase. In Arabidopsis, a putative CDC25 lacks a regulatory domain. Mitosis depends on correct temporal activity of CDKs, Aurora kinases and anaphase promotion complex; CDK-cyclin B activity beyond metaphase is catastrophic. Endoreduplication (re-replication of DNA in the absence of mitosis) is characterized by E2F expression and down-regulation of mitotic cyclins. Some cell size data support, whilst others negate, the idea of cell size having an impact on development.
Francis
Dennis
D
School of Biosciences, Cardiff University, PO Box 915, Cardiff CF10 3TL, UK.
D002453:Cell Cycle / Q000502:physiology*; D048429:Cell Size; D018844:Cyclin-Dependent Kinases / Q000502:physiology; D016213:Cyclins / Q000502:physiology; D017343:Genes, Plant; D018816:Genes, cdc; D059828:Plant Cells; D063245:Plant Development; D018521:Plant Physiological Phenomena; D018517:Plant Roots / Q000254:growth & development; D010944:Plants / Q000235:genetics
D016213:Cyclins; D018844:Cyclin-Dependent Kinases