Ethylene-Mediated Regulation of A2-Type CYCLINs Modulates Hyponastic Growth in Arabidopsis

• Published in: Plant physiology (Bethesda) Vol. 169; no. 1; pp. 194 - 208
• Main Authors: Polko, Joanna K., van Rooij, Jop A., Vanneste, Steffen, Pierik, Ronald, Ammerlaan, Ankie M.H., Vergeer-van Eijk, Marleen H., McLoughlin, Fionn, Gühl, Kerstin, Van Isterdael, Gert, Voesenek, Laurentius A.C.J., Millenaar, Frank F., Beeckman, Tom, Peeters, Anton J.M., Marée, Athanasius F.M., van Zanten, Martijn
• Format: Journal Article
• Language: English
• Published: United States American Society of Plant Biologists 01.09.2015
• Subjects: Arabidopsis - genetics; Arabidopsis - growth & development; Arabidopsis - physiology; Arabidopsis - radiation effects; Biology; Cell cycle; Cell division; Cell growth; Cell Proliferation; Cyclin A2 - genetics; Cyclin A2 - metabolism; Cyclins; Down-Regulation; Epidermal cells; Ethylenes - metabolism; FOCUS ON ETHYLENE; Gene Expression Regulation, Plant; Hypocotyl - genetics; Hypocotyl - growth & development; Hypocotyl - physiology; Hypocotyl - radiation effects; Laboratorium voor Moleculaire biologie; Laboratorium voor Plantenfysiologie; Laboratory of Molecular Biology; Laboratory of Plant Physiology; Light; Models, Biological; Petioles; Plant growth; Plant growth regulators; Plant Growth Regulators - metabolism; Plant Leaves - genetics; Plant Leaves - growth & development; Plant Leaves - physiology; Plant Leaves - radiation effects; Plants
• ISSN: 0032-0889; 1532-2548; 1532-2548
• DOI: 10.1104/pp.15.00343

Upward leaf movement (hyponastic growth) is frequently observed in response to changing environmental conditions and can be induced by the phytohormone ethylene. Hyponasty results from differential growth (i.e. enhanced cell elongation at the proximal abaxial side of the petiole relative to the adaxial side). Here, we characterizeEnhanced Hyponasty-D, an activation-tagged Arabidopsis (Arabidopsis thaliana) line with exaggerated hyponasty. This phenotype is associated with overexpression of the mitotic cyclinCYCLINA2;1(CYCA2;1), which hints at a role for cell divisions in regulating hyponasty. Indeed, mathematical analysis suggested that the observed changes in abaxial cell elongation rates during ethylene treatment should result in a larger hyponastic amplitude than observed, unless a decrease in cell proliferation rate at the proximal abaxial side of the petiole relative to the adaxial side was implemented. Our model predicts that when this differential proliferation mechanism is disrupted by either ectopic overexpression or mutation ofCYCA2;1, the hyponastic growth response becomes exaggerated. This is in accordance with experimental observations onCYCA2;1overexpression lines andcyca2;1knockouts. We therefore propose a bipartite mechanism controlling leaf movement: ethylene induces longitudinal cell expansion in the abaxial petiole epidermis to induce hyponasty and simultaneously affects its amplitude by controlling cell proliferation throughCYCA2;1. Further corroborating the model, we found that ethylene treatment results in transcriptional down-regulation ofA2-type CYCLINsand propose that this, and possibly other regulatory mechanisms affecting CYCA2;1, may contribute to this attenuation of hyponastic growth.