Despite being composed of immobile cells, plants reorient along directional stimuli. The hormone auxin is redistributed in stimulated organs leading to differential growth and bending. Auxin application triggers rapid cell wall acidification and elongation of aerial organs of plants, but the molecular players mediating these effects are still controversial. Here we use genetically-encoded pH and auxin signaling sensors, pharmacological and genetic manipulations available for Arabidopsis etiolated hypocotyls to clarify how auxin is perceived and the downstream growth executed. We show that auxin-induced acidification occurs by local activation of H+-ATPases, which in the context of gravity response is restricted to the lower organ side. This auxin-stimulated acidification and growth require TIR1/AFB-Aux/IAA nuclear auxin perception. In addition, auxin-induced gene transcription and specifically SAUR proteins are crucial downstream mediators of this growth. Our study provides strong experimental support for the acid growth theory and clarified the contribution of the upstream auxin perception mechanisms.
The authors express their gratitude to Veronika Bierbaum, Robert Hauschild for help with MATLAB, Daniel von Wangenheim for the gravitropism assay. We are thankful to Bill Gray, Mark Estelle, Michael Prigge, Ottoline Leyser, Claudia Oecking for sharing the seeds with us. We thank Katelyn Sageman-Furnas and the members of the Friml lab for critical reading of the manuscript. The research leading to these results has received funding from the People Programme (Marie Curie Actions) of the European Union’s Seventh Framework Programme (FP7/2007-2013) under REA grant agreement n° 291734. This work was also supported by the European Research Council (project ERC-2011-StG-20101109-PSDP).
Fendrych M, Leung J, Friml J. TIR1 AFB Aux IAA auxin perception mediates rapid cell wall acidification and growth of Arabidopsis hypocotyls. eLife. 2016;5. doi:10.7554/eLife.19048
Fendrych, M., Leung, J., & Friml, J. (2016). TIR1 AFB Aux IAA auxin perception mediates rapid cell wall acidification and growth of Arabidopsis hypocotyls. ELife, 5. https://doi.org/10.7554/eLife.19048
Fendrych, Matyas, Jeffrey Leung, and Jirí Friml. “TIR1 AFB Aux IAA Auxin Perception Mediates Rapid Cell Wall Acidification and Growth of Arabidopsis Hypocotyls.” ELife 5 (2016). https://doi.org/10.7554/eLife.19048.
M. Fendrych, J. Leung, and J. Friml, “TIR1 AFB Aux IAA auxin perception mediates rapid cell wall acidification and growth of Arabidopsis hypocotyls,” eLife, vol. 5, 2016.
Fendrych M, Leung J, Friml J. 2016. TIR1 AFB Aux IAA auxin perception mediates rapid cell wall acidification and growth of Arabidopsis hypocotyls. eLife. 5, e19048.
Fendrych, Matyas, et al. “TIR1 AFB Aux IAA Auxin Perception Mediates Rapid Cell Wall Acidification and Growth of Arabidopsis Hypocotyls.” ELife, vol. 5, e19048, eLife Sciences Publications, 2016, doi:10.7554/eLife.19048.