Hormonal control of cell division and elongation along differentiation trajectories in roots

• Published in: Journal of experimental botany Vol. 65; no. 10; pp. 2633 - 2643
• Main Authors: Takatsuka, Hirotomo, Umeda, Masaaki
• Format: Journal Article
• Language: English
• Published: England Oxford University Press [etc.] 01.06.2014; Oxford University Press
• Subjects: Arabidopsis - cytology; Auxins; Cell cycle; Cell Differentiation; Cell Division; Cell growth; Cytokinins; Gene expression; hormonal regulation; Plant cells; Plant growth regulators; Plant Growth Regulators - physiology; Plant roots; Plant Roots - cytology; Plant Stems - cytology; REVIEW PAPER; root growth; roots; Stem cells; cell elongation; cell division; endoreplication; Cell cycle; root; phytohormone
• ISSN: 0022-0957; 1460-2431
• DOI: 10.1093/jxb/ert485

The continuous development of roots is supported by a sustainable system for cell production and growth at the root tip. In the stem cell niche that consists of a quiescent centre and surrounding stem cells, an undifferentiated state and low mitotic activity are preserved by the action of auxin and abscisic acid. Stem cell daughters divide several times in the proximal meristem, where auxin and gibberellin mainly promote cell proliferation. Cells then elongate with the help of gibberellin, and become finally differentiated as a constituent of a cell file in the elongation/differentiation zone. In the model plant Arabidopsis thaliana, the transition zone is located between the proximal meristem and the elongation/differentiation zone, and plays an important role in switching from mitosis to the endoreplication that causes DNA polyploidization. Recent studies have shown that cytokinins are essentially required for this transition by antagonizing auxin signalling and promoting degradation of mitotic regulators. In each root zone, different phytohormones interact with one another and coordinately control cell proliferation, cell elongation, cell differentiation, and endoreplication. Such hormonal networks maintain the elaborate structure of the root tip under various environmental conditions. In this review, we summarize and discuss key issues related to hormonal regulation of root growth, and describe how phytohormones are associated with the control of cell cycle machinery.