A Mathematical Model for BRASSINOSTEROID INSENSITIVE1-Mediated Signaling in Root Growth and Hypocotyl Elongation

• Published in: Plant physiology (Bethesda) 2012-09, Vol.160 (1), p.523-532
• Main Authors: van Esse, G. Wilma, van Mourik, Simon, Stigter, Hans, Hove, Colette A. ten, Molenaar, Jaap, de Vries, Sacco C.
• Format: Article
• Language: English
• Subjects: Arabidopsis - drug effects; Arabidopsis - growth & development; Arabidopsis - metabolism; Arabidopsis Proteins - metabolism; Arabidopsis thaliana; Auxins; Biological and medical sciences; Brassinosteroids; Brassinosteroids - metabolism; Brassinosteroids - pharmacology; Computational Biology - methods; Culture Media - metabolism; Fundamental and applied biological sciences. Psychology; Green Fluorescent Proteins - metabolism; growth and development; Hypocotyl - drug effects; Hypocotyl - growth & development; Hypocotyl - metabolism; Hypocotyls; Ligands; loss-of-function mutation; Mathematical models; Modeling; Models, Theoretical; mutants; Plant physiology and development; Plant roots; Plant Roots - drug effects; Plant Roots - growth & development; Plant Roots - metabolism; Plants; Protein Kinases - metabolism; Receptors; Receptors, Cell Surface - metabolism; Root growth; roots; Signal Transduction; Steroids, Heterocyclic - metabolism; Steroids, Heterocyclic - pharmacology; SYSTEMS BIOLOGY, MOLECULAR BIOLOGY, AND GENE REGULATION; Triazoles - pharmacology
• ISSN: 0032-0889; 1532-2548; 1532-2548
• DOI: 10.1104/pp.112.200105

Brassinosteroid (BR) signaling is essential for plant growth and development. In Arabidopsis (Arabidopsis thaliana), BRs are perceived by the BRASSINOSTEROID INSENSITIVE1 (BRI1) receptor. Root growth and hypocotyl elongation are convenient downstream physiological outputs of BR signaling. A computational approach was employed to predict root growth solely on the basis of BRI1 receptor activity. The developed mathematical model predicts that during normal root growth, few receptors are occupied with ligand. The model faithfully predicts root growth, as observed in bri1 loss-of-function mutants. For roots, it incorporates one stimulatory and two inhibitory modules, while for hypocotyls, a single inhibitory module is sufficient. Root growth as observed when BRI1 is overexpressed can only be predicted assuming that a decrease occurred in the BRI1 half-maximum response values. Root growth appears highly sensitive to variation in BR concentration and much less to reduction in BRI1 receptor level, suggesting that regulation occurs primarily by ligand availability and biochemical activity.