Plant Cell Growth Signalling and Its Link to Ploidy

Takeshi Yoshizumi1 • Christian Breuer1'2 • Minami Matsui1 • Keiko Sugimoto-Shirasu1'2 (K)

1 Plant Science Center, RIKEN, Yokohama, 230-0045 Kanagawa, Japan [email protected]

2 Department of Cell and Developmental Biology, John Innes Centre, Norwich NR4 7UH, UK

Abstract What determines the final size of plant cells is a fundamental question in plant growth and development but the cellular mechanism that mediates this control remains largely unknown. Recent genetic studies using model plants Arabidopsis, maize and legume Medicago demonstrate that increasing DNA content or ploidy by a process called endoreduplication contributes to the post-mitotic cell expansion in higher plants. During successive rounds of endoreduplication or endocycle, cells replicate chromosomal DNA in the absence of mitosis, and the progression of the endocycle is both positively and negatively regulated by developmental and/or environmental signals. Plants also possess some ploidy-independent mechanism to control cell size and at least some part of this control involves a global feedback mechanism called organ-size checkpoint that balances cell proliferation and cell expansion within an organ to maintain its size homeostasis.

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