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One of the predominant cell-cycle programs found in mature tissues is endoreplication, also known as endoreduplication, that leads to cellular polyploidy. A key question for the understanding of endoreplication cycles is how oscillating levels of cyclin-dependent kinase activity are generated that control repeated rounds of DNA replication. The APC/C performs a pivotal function in the mitotic cell cycle by promoting anaphase and paving the road for a new round of DNA replication. However, using marker lines and plants in which APC/C components are knocked down, we show here that outgrowing and endoreplicating Arabidopsis leaf hairs display no or very little APC/C activity. Instead we find that RBX1-containing Cullin-RING E3 ubiquitin-Ligases (CRLs) are of central importance for the progression through endoreplication cycles; in particular, we have identified CULLIN4 as a major regulator of endoreplication in Arabidopsis trichomes. We have incorporated our findings into a bio-mathematical simulation presenting a robust two-step model of endoreplication control with one type of cyclin-dependent kinase inhibitor function for entry and a CRL-dependent oscillation of cyclin-dependent kinase activity via degradation of a second type of CDK inhibitor during endoreplication cycles.

Original publication

DOI

10.1073/pnas.1006941107

Type

Journal article

Journal

Proc Natl Acad Sci U S A

Publication Date

24/08/2010

Volume

107

Pages

15275 - 15280

Keywords

Arabidopsis, Arabidopsis Proteins, Carrier Proteins, Cell Cycle, Cullin Proteins, DNA Replication, DNA, Plant, Genes, Plant, Microscopy, Electron, Scanning, Models, Biological, Mutation, Plant Structures, Plants, Genetically Modified, Polyploidy, RNA Interference