article published yes Lanxin Li author 367EF8FA-F248-11E8-B48F-1D18A9856A870000-0002-5607-272X Inge Verstraeten author 362BF7FE-F248-11E8-B48F-1D18A9856A870000-0001-7241-2328 Mark Roosjen author Koji Takahashi author Lesia Rodriguez Solovey author 3922B506-F248-11E8-B48F-1D18A9856A870000-0002-7244-7237 Jack Merrin author 4515C308-F248-11E8-B48F-1D18A9856A870000-0001-5145-4609 Jian Chen author Lana Shabala author Wouter Smet author Hong Ren author Steffen Vanneste author Sergey Shabala author Bert De Rybel author Dolf Weijers author Toshinori Kinoshita author William M. Gray author Jiří Friml author 4159519E-F248-11E8-B48F-1D18A9856A870000-0002-8302-7596 JiFr department NanoFab department Tracing Evolution of Auxin Transport and Polarity in Plants project Molecular mechanisms of endocytic cargo recognition in plants project International IST Doctoral Program project A Case Study of Plant Growth Regulation: Molecular Mechanism of Auxin-mediated Rapid Growth Inhibition in Arabidopsis Root project Growth regulation tailors development in plants to their environment. A prominent example of this is the response to gravity, in which shoots bend up and roots bend down1. This paradox is based on opposite effects of the phytohormone auxin, which promotes cell expansion in shoots while inhibiting it in roots via a yet unknown cellular mechanism2. Here, by combining microfluidics, live imaging, genetic engineering and phosphoproteomics in Arabidopsis thaliana, we advance understanding of how auxin inhibits root growth. We show that auxin activates two distinct, antagonistically acting signalling pathways that converge on rapid regulation of apoplastic pH, a causative determinant of growth. Cell surface-based TRANSMEMBRANE KINASE1 (TMK1) interacts with and mediates phosphorylation and activation of plasma membrane H+-ATPases for apoplast acidification, while intracellular canonical auxin signalling promotes net cellular H+ influx, causing apoplast alkalinization. Simultaneous activation of these two counteracting mechanisms poises roots for rapid, fine-tuned growth modulation in navigating complex soil environments. Springer Nature2021 eng Multidisciplinary 0028-0836 1476-4687 34707283 00071333810000610.1038/s41586-021-04037-6 5997884273-277 https://research-explorer.ista.ac.at/record/10095 https://ist.ac.at/en/news/stop-and-grow/ Li, L., Verstraeten, I., Roosjen, M., Takahashi, K., Rodriguez Solovey, L., Merrin, J., … Friml, J. (2021). Cell surface and intracellular auxin signalling for H⁺ fluxes in root growth. <i>Nature</i>. Springer Nature. <a href="https://doi.org/10.1038/s41586-021-04037-6">https://doi.org/10.1038/s41586-021-04037-6</a> L. Li <i>et al.</i>, “Cell surface and intracellular auxin signalling for H⁺ fluxes in root growth,” <i>Nature</i>, vol. 599, no. 7884. Springer Nature, pp. 273–277, 2021. L. Li, I. Verstraeten, M. Roosjen, K. Takahashi, L. Rodriguez Solovey, J. Merrin, J. Chen, L. Shabala, W. Smet, H. Ren, S. Vanneste, S. Shabala, B. De Rybel, D. Weijers, T. Kinoshita, W.M. Gray, J. Friml, Nature 599 (2021) 273–277. Li L, Verstraeten I, Roosjen M, Takahashi K, Rodriguez Solovey L, Merrin J, Chen J, Shabala L, Smet W, Ren H, Vanneste S, Shabala S, De Rybel B, Weijers D, Kinoshita T, Gray WM, Friml J. 2021. Cell surface and intracellular auxin signalling for H⁺ fluxes in root growth. Nature. 599(7884), 273–277. Li L, Verstraeten I, Roosjen M, et al. Cell surface and intracellular auxin signalling for H⁺ fluxes in root growth. <i>Nature</i>. 2021;599(7884):273-277. doi:<a href="https://doi.org/10.1038/s41586-021-04037-6">10.1038/s41586-021-04037-6</a> Li, Lanxin, Inge Verstraeten, Mark Roosjen, Koji Takahashi, Lesia Rodriguez Solovey, Jack Merrin, Jian Chen, et al. “Cell Surface and Intracellular Auxin Signalling for H⁺ Fluxes in Root Growth.” <i>Nature</i>. Springer Nature, 2021. <a href="https://doi.org/10.1038/s41586-021-04037-6">https://doi.org/10.1038/s41586-021-04037-6</a>. Li, Lanxin, et al. “Cell Surface and Intracellular Auxin Signalling for H⁺ Fluxes in Root Growth.” <i>Nature</i>, vol. 599, no. 7884, Springer Nature, 2021, pp. 273–77, doi:<a href="https://doi.org/10.1038/s41586-021-04037-6">10.1038/s41586-021-04037-6</a>. 102232021-11-07T23:01:25Z2025-07-10T11:49:46Z