The DP-E2F-like Gene DEL1 Controls the Endocycle in Arabidopsis thaliana

• Published in: Current biology 2005-01, Vol.15 (1), p.59-63
• Main Authors: Vlieghe, Kobe, Boudolf, Véronique, Beemster, Gerrit T.S., Maes, Sara, Magyar, Zoltan, Atanassova, Ana, de Almeida Engler, Janice, De Groodt, Ruth, Inzé, Dirk, De Veylder, Lieven
• Format: Article
• Language: English
• Subjects: Arabidopsis - genetics; Arabidopsis - growth & development; Arabidopsis Proteins - physiology; Biomechanical Phenomena; Cell Cycle Proteins - physiology; DNA Primers; DNA Replication - genetics; DNA Replication - physiology; DNA-Binding Proteins - physiology; E2F Transcription Factors; E2F7 Transcription Factor; Flow Cytometry; Gene Expression Regulation, Plant; In Situ Hybridization; Plant Leaves - genetics; Plant Leaves - growth & development; Plants, Genetically Modified; Ploidies; Reverse Transcriptase Polymerase Chain Reaction; Transcription Factors - physiology
• ISSN: 0960-9822; 1879-0445
• DOI: 10.1016/j.cub.2004.12.038

Endoreduplication or DNA replication without mitosis is widespread in nature. Well-known examples are fruit fly polytene chromosomes and cereal endosperm. Although endocycles are thought to be driven by the same regulators as those that control the G1-S transition of the mitotic cell cycle, the molecular mechanisms that differentiate mitotically dividing cells from endoreduplicating ones are largely unknown. A novel class of atypical E2F-like proteins has recently been identified and is designated E2F7 in mammals [1, 2] and DP-E2F-like (DEL) in Arabidopsis thaliana[3–5]. We demonstrate that loss of DEL1 function resulted in increased ploidy levels, whereas ectopic expression of DEL1 reduced endoreduplication. Ploidy changes were correlated with altered expression of a subset of E2F target genes encoding proteins necessary for DNA replication. Because DEL1 proteins were postulated to antagonize the E2F pathway, we generated DEL1-E2Fa-DPa triple transgenics. DEL1 inhibited the endoreduplication phenotype, but not the ectopic cell divisions that resulted from the overexpression of both E2Fa and DPa, illustrating that DEL1 specifically represses the endocycle. Because DEL1 transcripts were detected exclusively in mitotically dividing cells, we conclude that DEL1 is an important novel inhibitor of the endocycle and preserves the mitotic state of proliferating cells by suppressing transcription of genes that are required for cells to enter the DNA endoreduplication cycle.