The balance between cell division and endoreplication depends on E2FC-DPB, transcription factors regulated by the ubiquitin-SCFSKP2A pathway in Arabidopsis.

Abstract	The balance between cell proliferation, cell cycle arrest, and differentiation needed to maintain the organogenetic program depends on the coordination of gene expression, posttranslational modification, and specific proteolysis of cell cycle regulators. The G1/S and G2/M transitions are critical checkpoints controlled, in part, by cyclin-dependent kinases in the retinoblastoma (RBR)/E2F/DP pathway. Arabidopsis thaliana DPB is regulated by phosphorylation and targeted to proteasome-mediated proteolysis by the SCF(SKP2A) complex. In addition, DPB interacts in vivo with E2FC, because ectopic coexpression of E2FC and DPB produces severe developmental defects. To understand E2FC/DPB heterodimer function, we analyzed the effect of reducing E2FC mRNA levels with RNA interference. The e2fc-R plants developed organs with more but smaller cells and showed increased cell cycle marker gene expression and increased proliferative activity in developing leaves, meristems, and pericycle cells. This last feature produces plants with more lateral roots, consistent with an E2FC role in restricting lateral root initiation. The e2fc-R plants also show marked reductions in ploidy levels of mature leaves. These results indicate that the transition from cell division to the endocycle is sensitive to different pathways, E2FC/DPB being one of them. Our results show that E2FC/DPB is a key factor in controlling the balance between cell proliferation and the switch to the endocycle program.
Authors	Juan C del Pozo, Sara Diaz-Trivino, Nerea Cisneros, Crisanto Gutierrez
Journal	The Plant cell (Plant Cell) Vol. 18 Issue 9 Pg. 2224-35 (Sep 2006) ISSN: 1040-4651 [Print] England
PMID	16920782 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
Chemical References	Arabidopsis Proteins CycB1 protein, Arabidopsis Cyclin B DP transcription factor, plant DPb protein, Arabidopsis E2F Transcription Factors E2FC protein, Arabidopsis F-Box Proteins Genetic Markers Indoleacetic Acids Plant Growth Regulators Plant Proteins RNA, Messenger S-Phase Kinase-Associated Proteins Transcription Factors Ubiquitin
Topics	Arabidopsis (cytology, metabolism, physiology) Arabidopsis Proteins (genetics, metabolism, physiology) Cell Division (physiology) Cell Proliferation Cyclin B (metabolism) E2F Transcription Factors (genetics, metabolism, physiology) F-Box Proteins (metabolism) Gene Expression Regulation, Plant Genetic Markers Indoleacetic Acids (pharmacology) Meristem (cytology, drug effects, physiology) Phosphorylation Plant Growth Regulators (pharmacology) Plant Leaves (cytology, genetics, metabolism) Plant Proteins Plant Roots (cytology, drug effects, physiology) Ploidies RNA Interference RNA, Messenger (metabolism) S-Phase Kinase-Associated Proteins (metabolism) Transcription Factors (genetics, metabolism, physiology) Ubiquitin (metabolism)

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