Light-Dependent Regulation ofDEL1Is Determined by the Antagonistic Action of E2Fb and E2Fc

Barbara Berckmans,Hilde Van Den Daele,Lieven De Veylder,Zoltan Magyar,Laszlo Bögre,Tim Lammens

doi:10.1104/pp.111.183384

Barbara Berckmans, Hilde Van Den Daele + Show 4 more

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https://doi.org/10.1104/pp.111.183384

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Journal: Plant Physiology	Publication Date: Sep 9, 2011
Citations: 59	License type: CC BY 4.0

Affiliation: Institute of Plant Biology

Abstract

Endoreduplication represents a variation on the cell cycle in which multiple rounds of DNA replication occur without subsequent chromosome separation and cytokinesis, thereby increasing the cellular DNA content. It is known that the DNA ploidy level of cells is controlled by external stimuli such as light; however, limited knowledge is available on how environmental signals regulate the endoreduplication cycle at the molecular level. Previously, we had demonstrated that the conversion from a mitotic cell cycle into an endoreduplication cycle is controlled by the atypical E2F transcription factor, DP-E2F-LIKE1 (DEL1), that represses the endocycle onset. Here, the Arabidopsis (Arabidopsis thaliana) DEL1 gene was identified as a transcriptional target of the classical E2Fb and E2Fc transcription factors that antagonistically control its transcript levels through competition for a single E2F cis-acting binding site. In accordance with the reported opposite effects of light on the protein levels of E2Fb and E2Fc, DEL1 transcription depended on the light regime. Strikingly, modified DEL1 expression levels uncoupled the link between light and endoreduplication in hypocotyls, implying that DEL1 acts as a regulatory connection between endocycle control and the photomorphogenic response.

Highlights

Endoreduplication represents a variation on the cell cycle in which multiple rounds of DNA replication occur without subsequent chromosome separation and cytokinesis, thereby increasing the cellular DNA content
To get insight into how DEL1 expression might be regulated, we focused on the two putative E2F cis-acting elements present in its promoter
An analogous interaction between different types of E2Fs has been observed in mammals, in which E2F7 and E2F8, the mammalian homologs of the DEL1 gene, are regulated by the classical E2F1 (Di Stefano et al, 2003; Christensen et al, 2005), indicating that the interplay between typical and atypical E2Fs is evolutionarily conserved

Summary

Introduction

Endoreduplication represents a variation on the cell cycle in which multiple rounds of DNA replication occur without subsequent chromosome separation and cytokinesis, thereby increasing the cellular DNA content. It involves the production of new cells that arise at the meristems from divisions of pluripotent stem cells, followed by their successive cell cycle exit and differentiation Due to their sessile life style, plants are exposed to changing environmental conditions and are continuously forced to adapt their body plan (Walter et al, 2009; Skirycz and Inze, 2010). Typical E2F factors need to dimerize with a DP to gain a high DNA-binding specificity, which is not the case for atypical ones because they possess two DNA-binding domains and, can bind DNA as monomers Both E2Fa and E2Fb are transcriptional cell cycle activators, and their overproduction enhances cell proliferation (De Veylder et al, 2002; Magyar et al, 2005; Sozzani et al, 2006). Mitotic cell cycle progression and endoreduplication are intimately linked during organ development, in which a cell proliferation phase is followed by

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