Poster: Late and Moved Abstracts

Abs # 952: Degradation of KRP1 by an SCF ubiquitin ligase and cell cycle control in Arabidopsis

Presenter:	Ren, Hong , hren@indiana.edu
Authors	Ren, Hong  (A)   Murray, James A. H. (B)   Estelle, Mark  (A)
Affiliations:	(A): Department of Biology, Indiana University (B): Institute of Biotechnology, University of Cambridge, UK

How cell division is regulated is a fundamental question in biology. In eukaryotes, one of the key mechanisms that control cell division is the regulation of the G1-S phase transition of the cell cycle by SCF ubiquitin ligase-dependent proteolysis. Compared with yeast and animals, little is known about the role of SCF E3s in plant cell cycle regulation. In order to gain more insight into the mechanisms by which plant cell division is regulated, we are studying the cyclin-dependent kinase inhibitor KRP1, a negative regulator of the cell cycle. The role of KRP1 in cell cycle control and pericycle cell division during early lateral root initiation and the degradation of KRP1 by ubiquitin-mediated proteolysis are being investigated. Our studies show that KRP1 may be involved in the regulation of xylem-pole pericycle cell division during early lateral root initiation. KRP1 interacts with CDKA;1/D-type cyclin complex in planta and may be involved in the regulation of the G1-S phase transition of the cell cycle. KRP1 is an unstable protein in planta and is degraded by the 26S proteasome. Further, KRP1 is degraded by an SCF ubiquitin ligase, which is composed of RBX1At, CUL1At, ASK1, and an unknown F-box protein. In addition, the AXR1-dependent RUB conjugation pathway regulates KRP1 degradation. The results of these studies indicate that an SCF ubiquitin ligase is involved in the degradation of KRP1 to regulate the G1-S phase transition of the cell cycle.