@unpublished{21994, abstract = {Adaptive plant development is orchestrated, among others, by directional, intercellular transport of the phytohormone auxin. Self-organizing development, such as flexible vasculature formation, depends on so-called auxin canalization, manifested by the gradual formation of auxin transport channels through feedback between auxin signalling and transport. Herein, we identify MAKR6 as an important, novel component in this feedback. MAKR6 expression accumulates strongly in vascular cells and is tightly regulated by auxin via the Aux/IAA-ARF-WRKY23 transcriptional network. MAKR6 is required for auxin canalization-dependent processes, including leaf venation, vasculature regeneration, and de novo auxin channel formation from local auxin sources. Mechanistically, MAKR6 interacts with the PIN1 auxin transporter, modulating its trafficking and polarization. MAKR6 also associates with and integrates two key receptor-like kinase complexes involved in canalization, TMK1/4 and the CAMEL-CANAR. Together, our study establishes MAKR6 as a multifaceted regulator that couples transcriptional auxin signalling to PIN1 repolarization and coordinates multiple RLK-mediated signalling pathways during canalization. This provides mechanistic insights into auxin canalization and exemplifies a framework for exploring similar regulatory nodes in other developmental contexts.}, author = {Ge, Zengxiang and Koczka, Lilla and Mazur, Ewa and Molnar, Gergely and Vladimirtsev, Dmitrii and Kassem, Nada and Ait Ikene, Sara and Fiedler, Lukas and Friml, Jiří}, booktitle = {bioRxiv}, title = {{MAKR6 integrates TMK and CAMEL/CANAR signalling for auxin canalization in Arabidopsis}}, doi = {10.1101/2025.10.07.680881}, year = {2026}, } @article{21490, abstract = {Auxin canalization is a self-organizing process that governs the flexible formation of vasculature by reinforcing the formation of auxin transport channels. A key prerequisite is the feedback between auxin signaling and directional auxin transport, mediated by PIN transporters. Despite the developmental importance of canalization, the molecular components linking auxin perception to the regulation of PIN auxin transporters remain poorly understood. Here, we identify TOW, a novel and essential component of auxin canalization that links intracellular auxin signaling with cell surface auxin perception. TOW is regulated downstream of TIR1/AFB-Aux/IAA-WRKY23 transcriptional auxin signaling. tow mutants exhibit defects in regeneration and de novo vasculature formation, along with impaired formation of polarized, PIN-expressing auxin channels. At the subcellular level, these mutants display disrupted auxin-induced PIN polarization and altered PIN endocytic trafficking dynamics. TOW localizes predominantly to the plasma membrane, where it interacts with receptor-like kinases involved in auxin canalization, including the TMK1 auxin co-receptor and the CAMEL-CANAR complex. TOW promotes PIN interaction with these kinases and stabilizes PINs at the cell surface. Together, our findings identify TOW as a molecular link between intracellular and cell surface auxin signaling mechanisms that converge on PIN trafficking and polarity, providing new insights into how auxin signaling regulates directional auxin transport for the self-organizing formation of vasculature during flexible plant development.}, author = {Li, Mingyue and Rydza, Nikola and Mazur, Ewa and Molnar, Gergely and Nodzyński, Tomasz and Friml, Jiří}, issn = {0960-9822}, journal = {Current Biology}, number = {6}, pages = {1468--1480.e6}, publisher = {Elsevier}, title = {{Receptor-like-kinase-interacting protein TOW stabilizes PIN transporters for auxin canalization}}, doi = {10.1016/j.cub.2026.02.023}, volume = {36}, year = {2026}, } @article{20656, abstract = {Phytohormone auxin and its directional transport mediate much of the remarkably plastic development of higher plants. Positive feedback between auxin signaling and transport is a prerequisite for (1) self-organizing processes, including vascular tissue formation, and (2) directional growth responses such as gravitropism. Here, we identify a mechanism by which auxin signaling directly targets PIN auxin transporters. Via the cell-surface AUXIN-BINDING PROTEIN1 (ABP1)-TRANSMEMBRANE KINASE 1 (TMK1) receptor module, auxin rapidly induces phosphorylation and thus stabilization of PIN2. Following gravistimulation, initial auxin asymmetry activates autophosphorylation of the TMK1 kinase. This induces TMK1 interaction with and phosphorylation of PIN2, stabilizing PIN2 at the lower root side, thus reinforcing asymmetric auxin flow for root bending. Upstream of TMK1 in this regulation, ABP1 acts redundantly with the root-expressed ABP1-LIKE 3 (ABL3) auxin receptor. Such positive feedback between cell-surface auxin signaling and PIN-mediated polar auxin transport is fundamental for robust root gravitropism and presumably for other self-organizing developmental phenomena.}, author = {Rodriguez Solovey, Lesia and Fiedler, Lukas and Zou, Minxia and Giannini, Caterina and Monzer, Aline and Vladimirtsev, Dmitrii and Randuch, Marek and Yu, Yongfan and Gelová, Zuzana and Verstraeten, Inge and Hajny, Jakub and Chen, Meng and Tan, Shutang and Hörmayer, Lukas and Li, Lanxin and Marques-Bueno, Maria Mar and Quddoos, Zainab and Molnar, Gergely and Kulich, Ivan and Jaillais, Yvon and Friml, Jiří}, issn = {0092-8674}, journal = {Cell}, number = {22}, pages = {6138--6150.e17}, publisher = {Elsevier}, title = {{ABP1/ABL3-TMK1 cell-surface auxin signaling targets PIN2-mediated auxin fluxes for root gravitropism}}, doi = {10.1016/j.cell.2025.08.026}, volume = {188}, year = {2025}, } @unpublished{19399, abstract = {Phytohormone auxin and its directional transport mediate much of the remarkably plastic development of higher plants. Positive feedback between auxin signaling and transport is a key prerequisite for (i) self-organizing processes including vascular tissue formation and (ii) directional growth responses such as gravitropism. Here we identify a mechanism, by which auxin signaling directly targets PIN auxin transporters. Via the cell-surface ABP1-TMK1 receptor module, auxin rapidly induces phosphorylation and thus stabilization of PIN2. Following gravistimulation, initial auxin asymmetry activates autophosphorylation of the TMK1 kinase. This induces TMK1 interaction with and phosphorylation of PIN2, stabilizing PIN2 at the lower root side, thus reinforcing asymmetric auxin flow for root bending. Upstream of TMK1 in this regulation, ABP1 acts redundantly with the root-expressed ABP1-LIKE auxin receptor ABL3. Such positive feedback between cell-surface auxin signaling and PIN-mediated polar auxin transport is fundamental for robust root gravitropism and presumably also for other self-organizing developmental phenomena.}, author = {Rodriguez Solovey, Lesia and Fiedler, Lukas and Zou, Minxia and Giannini, Caterina and Monzer, Aline and Vladimirtsev, Dmitrii and Randuch, Marek and Yu, Yongfan and Gelová, Zuzana and Verstraeten, Inge and Hajny, Jakub and Chen, Meng and Tan, Shutang and Hörmayer, Lukas and Li, Lanxin and Marques-Bueno, Maria Mar and Quddoos, Zainab and Molnar, Gergely and Xu, Tongda and Kulich, Ivan and Jaillais, Yvon and Friml, Jiří}, booktitle = {bioRxiv}, title = {{ABP1/ABL3-TMK1 cell-surface auxin signaling directly targets PIN2-mediated auxin fluxes for root gravitropism}}, doi = {10.1101/2022.11.30.518503}, year = {2025}, } @article{14339, abstract = {Lateral roots are typically maintained at non-vertical angles with respect to gravity. These gravitropic setpoint angles are intriguing because their maintenance requires that roots are able to effect growth response both with and against the gravity vector, a phenomenon previously attributed to gravitropism acting against an antigravitropic offset mechanism. Here we show how the components mediating gravitropism in the vertical primary root—PINs and phosphatases acting upon them—are reconfigured in their regulation such that lateral root growth at a range of angles can be maintained. We show that the ability of Arabidopsis lateral roots to bend both downward and upward requires the generation of auxin asymmetries and is driven by angle-dependent variation in downward gravitropic auxin flux acting against angle-independent upward, antigravitropic flux. Further, we demonstrate a symmetry in auxin distribution in lateral roots at gravitropic setpoint angle that can be traced back to a net, balanced polarization of PIN3 and PIN7 auxin transporters in the columella. These auxin fluxes are shifted by altering PIN protein phosphoregulation in the columella, either by introducing PIN3 phosphovariant versions or via manipulation of levels of the phosphatase subunit PP2A/RCN1. Finally, we show that auxin, in addition to driving lateral root directional growth, acts within the lateral root columella to induce more vertical growth by increasing RCN1 levels, causing a downward shift in PIN3 localization, thereby diminishing the magnitude of the upward, antigravitropic auxin flux.}, author = {Roychoudhry, S and Sageman-Furnas, K and Wolverton, C and Grones, Peter and Tan, Shutang and Molnar, Gergely and De Angelis, M and Goodman, HL and Capstaff, N and JPB, Lloyd and Mullen, J and Hangarter, R and Friml, Jiří and Kepinski, S}, issn = {2055-0278}, journal = {Nature Plants}, pages = {1500--1513}, publisher = {Springer Nature}, title = {{Antigravitropic PIN polarization maintains non-vertical growth in lateral roots}}, doi = {10.1038/s41477-023-01478-x}, volume = {9}, year = {2023}, } @article{9290, abstract = {Polar subcellular localization of the PIN exporters of the phytohormone auxin is a key determinant of directional, intercellular auxin transport and thus a central topic of both plant cell and developmental biology. Arabidopsis mutants lacking PID, a kinase that phosphorylates PINs, or the MAB4/MEL proteins of unknown molecular function display PIN polarity defects and phenocopy pin mutants, but mechanistic insights into how these factors convey PIN polarity are missing. Here, by combining protein biochemistry with quantitative live-cell imaging, we demonstrate that PINs, MAB4/MELs, and AGC kinases interact in the same complex at the plasma membrane. MAB4/MELs are recruited to the plasma membrane by the PINs and in concert with the AGC kinases maintain PIN polarity through limiting lateral diffusion-based escape of PINs from the polar domain. The PIN-MAB4/MEL-PID protein complex has self-reinforcing properties thanks to positive feedback between AGC kinase-mediated PIN phosphorylation and MAB4/MEL recruitment. We thus uncover the molecular mechanism by which AGC kinases and MAB4/MEL proteins regulate PIN localization and plant development.}, author = {Glanc, Matous and Van Gelderen, K and Hörmayer, Lukas and Tan, Shutang and Naramoto, S and Zhang, Xixi and Domjan, David and Vcelarova, L and Hauschild, Robert and Johnson, Alexander J and de Koning, E and van Dop, M and Rademacher, E and Janson, S and Wei, X and Molnar, Gergely and Fendrych, Matyas and De Rybel, B and Offringa, R and Friml, Jiří}, issn = {1879-0445}, journal = {Current Biology}, number = {9}, pages = {1918--1930}, publisher = {Elsevier}, title = {{AGC kinases and MAB4/MEL proteins maintain PIN polarity by limiting lateral diffusion in plant cells}}, doi = {10.1016/j.cub.2021.02.028}, volume = {31}, year = {2021}, } @article{7600, abstract = {Directional intercellular transport of the phytohormone auxin mediated by PIN FORMED (PIN) efflux carriers plays essential roles in both coordinating patterning processes and integrating multiple external cues by rapidly redirecting auxin fluxes. Multilevel regulations of PIN activity under internal and external cues are complicated; however, the underlying molecular mechanism remains elusive. Here we demonstrate that 3’-Phosphoinositide-Dependent Protein Kinase1 (PDK1), which is conserved in plants and mammals, functions as a molecular hub integrating the upstream lipid signalling and the downstream substrate activity through phosphorylation. Genetic analysis uncovers that loss-of-function Arabidopsis mutant pdk1.1 pdk1.2 exhibits a plethora of abnormalities in organogenesis and growth, due to the defective PIN-dependent auxin transport. Further cellular and biochemical analyses reveal that PDK1 phosphorylates D6 Protein Kinase to facilitate its activity towards PIN proteins. Our studies establish a lipid-dependent phosphorylation cascade connecting membrane composition-based cellular signalling with plant growth and patterning by regulating morphogenetic auxin fluxes.}, author = {Tan, Shutang and Zhang, Xixi and Kong, Wei and Yang, Xiao-Li and Molnar, Gergely and Vondráková, Zuzana and Filepová, Roberta and Petrášek, Jan and Friml, Jiří and Xue, Hong-Wei}, issn = {2055-0278}, journal = {Nature Plants}, pages = {556--569}, publisher = {Springer Nature}, title = {{The lipid code-dependent phosphoswitch PDK1–D6PK activates PIN-mediated auxin efflux in Arabidopsis}}, doi = {10.1038/s41477-020-0648-9}, volume = {6}, year = {2020}, } @article{8721, abstract = {Spontaneously arising channels that transport the phytohormone auxin provide positional cues for self-organizing aspects of plant development such as flexible vasculature regeneration or its patterning during leaf venation. The auxin canalization hypothesis proposes a feedback between auxin signaling and transport as the underlying mechanism, but molecular players await discovery. We identified part of the machinery that routes auxin transport. The auxin-regulated receptor CAMEL (Canalization-related Auxin-regulated Malectin-type RLK) together with CANAR (Canalization-related Receptor-like kinase) interact with and phosphorylate PIN auxin transporters. camel and canar mutants are impaired in PIN1 subcellular trafficking and auxin-mediated PIN polarization, which macroscopically manifests as defects in leaf venation and vasculature regeneration after wounding. The CAMEL-CANAR receptor complex is part of the auxin feedback that coordinates polarization of individual cells during auxin canalization.}, author = {Hajny, Jakub and Prat, Tomas and Rydza, N and Rodriguez Solovey, Lesia and Tan, Shutang and Verstraeten, Inge and Domjan, David and Mazur, E and Smakowska-Luzan, E and Smet, W and Mor, E and Nolf, J and Yang, B and Grunewald, W and Molnar, Gergely and Belkhadir, Y and De Rybel, B and Friml, Jiří}, issn = {1095-9203}, journal = {Science}, number = {6516}, pages = {550--557}, publisher = {American Association for the Advancement of Science}, title = {{Receptor kinase module targets PIN-dependent auxin transport during canalization}}, doi = {10.1126/science.aba3178}, volume = {370}, year = {2020}, } @article{7427, abstract = {Plants, like other multicellular organisms, survive through a delicate balance between growth and defense against pathogens. Salicylic acid (SA) is a major defense signal in plants, and the perception mechanism as well as downstream signaling activating the immune response are known. Here, we identify a parallel SA signaling that mediates growth attenuation. SA directly binds to A subunits of protein phosphatase 2A (PP2A), inhibiting activity of this complex. Among PP2A targets, the PIN2 auxin transporter is hyperphosphorylated in response to SA, leading to changed activity of this important growth regulator. Accordingly, auxin transport and auxin-mediated root development, including growth, gravitropic response, and lateral root organogenesis, are inhibited. This study reveals how SA, besides activating immunity, concomitantly attenuates growth through crosstalk with the auxin distribution network. Further analysis of this dual role of SA and characterization of additional SA-regulated PP2A targets will provide further insights into mechanisms maintaining a balance between growth and defense.}, author = {Tan, Shutang and Abas, Melinda F and Verstraeten, Inge and Glanc, Matous and Molnar, Gergely and Hajny, Jakub and Lasák, Pavel and Petřík, Ivan and Russinova, Eugenia and Petrášek, Jan and Novák, Ondřej and Pospíšil, Jiří and Friml, Jiří}, issn = {09609822}, journal = {Current Biology}, number = {3}, pages = {381--395.e8}, publisher = {Cell Press}, title = {{Salicylic acid targets protein phosphatase 2A to attenuate growth in plants}}, doi = {10.1016/j.cub.2019.11.058}, volume = {30}, year = {2020}, } @article{449, abstract = {Auxin is unique among plant hormones due to its directional transport that is mediated by the polarly distributed PIN auxin transporters at the plasma membrane. The canalization hypothesis proposes that the auxin feedback on its polar flow is a crucial, plant-specific mechanism mediating multiple self-organizing developmental processes. Here, we used the auxin effect on the PIN polar localization in Arabidopsis thaliana roots as a proxy for the auxin feedback on the PIN polarity during canalization. We performed microarray experiments to find regulators of this process that act downstream of auxin. We identified genes that were transcriptionally regulated by auxin in an AXR3/IAA17- and ARF7/ARF19-dependent manner. Besides the known components of the PIN polarity, such as PID and PIP5K kinases, a number of potential new regulators were detected, among which the WRKY23 transcription factor, which was characterized in more detail. Gain- and loss-of-function mutants confirmed a role for WRKY23 in mediating the auxin effect on the PIN polarity. Accordingly, processes requiring auxin-mediated PIN polarity rearrangements, such as vascular tissue development during leaf venation, showed a higher WRKY23 expression and required the WRKY23 activity. Our results provide initial insights into the auxin transcriptional network acting upstream of PIN polarization and, potentially, canalization-mediated plant development.}, author = {Prat, Tomas and Hajny, Jakub and Grunewald, Wim and Vasileva, Mina K and Molnar, Gergely and Tejos, Ricardo and Schmid, Markus and Sauer, Michael and Friml, Jirí}, journal = {PLoS Genetics}, number = {1}, publisher = {Public Library of Science}, title = {{WRKY23 is a component of the transcriptional network mediating auxin feedback on PIN polarity}}, doi = {10.1371/journal.pgen.1007177}, volume = {14}, year = {2018}, } @article{1345, abstract = {The electrostatic charge at the inner surface of the plasma membrane is strongly negative in higher organisms. A new study shows that phosphatidylinositol-4-phosphate plays a critical role in establishing plasma membrane surface charge in Arabidopsis, which regulates the correct localization of signalling components.}, author = {Molnar, Gergely and Fendrych, Matyas and Friml, Jirí}, journal = {Nature Plants}, publisher = {Nature Publishing Group}, title = {{Plasma membrane: Negative attraction}}, doi = {10.1038/nplants.2016.102}, volume = {2}, year = {2016}, }