@article{21763,
  abstract     = {Reactive oxygen species (ROS) have been implicated in multiple signaling processes in plants, but the underlying mechanisms and roles remain enigmatic. In this study, we developed a method of live imaging of apoplastic ROS at the root surface. Distinct signals, including auxin, extracellular adenosine triphosphate, and rapid alkalinization factor 1 peptide, induce cytosolic calcium transients and apoplastic ROS bursts. Genetic and optogenetic manipulations of Arabidopsis identified calcium transients as necessary and sufficient for ROS bursts through activation of reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidases RBOHC and RBOHF. Apoplastic ROS bursts are not required, but they do limit gravity-induced root bending. Root bending is sensed by the stretch-activated calcium channel MCA1, leading to NADPH oxidase activation. The resulting ROS production stiffens cell walls to facilitate soil penetration. Apoplastic ROS thus provides a means to balance tissue flexibility and stiffness to navigate soil.},
  author       = {Kulich, Ivan and Vladimirtsev, Dmitrii and Randuch, Marek and Gao, Shiqiang and Citterico, Matteo and Konrad, Kai R. and Nagel, Georg and Wrzaczek, Michael and Cascaro, Léa and Vinet, Pauline and Durand, Pauline and Asnacios, Atef and Verma, Lokesh and Bennett, Malcolm J. and Pandey, Bipin K. and Friml, Jiří},
  issn         = {1095-9203},
  journal      = {Science},
  number       = {6795},
  pages        = {296--300},
  publisher    = {AAAS},
  title        = {{Calcium-triggered apoplastic ROS bursts balance gravity and mechanical signals for soil navigation}},
  doi          = {10.1126/science.adu8197},
  volume       = {392},
  year         = {2026},
}

@unpublished{20982,
  abstract     = {Plant cells respond to a wide range of stimuli through intracellular calcium (Ca2+) signaling. Cyclic nucleotide-gated channels (CNGCs) are a major class of plant Ca2+ channels, with 20 homologs in Arabidopsis. These tetrameric plasma membrane proteins act downstream of diverse signals, such as phytohormones, extracellular damage, cell wall integrity or temperature. Here, we identify a class of plant-specific proteins, Armadillo Repeat Only (ARO), as essential regulators of possibly all plant CNGCs. Abrogation of functional sporophytic AROs results in a phenotypic pattern strongly reminiscent of CNGC dysfunction, including defects in root gravitropism, root hair growth and morphology, stomatal movement, and responses to extracellular ATP and the phytohormone auxin. aro2/3/4 mutants are fully resistant to the toxic effects caused by overexpression of CNGCs. AROs colocalize and physically interact with multiple CNGCs and modulate CNGC-dependent currents in Xenopus oocytes. Structural modeling and site-directed mutagenesis reveal AROs tetramer formation surrounding the CNGC channel, interacting via its IQ domain. Taken together, plant CNGC channels don’t act alone, but in a larger complex - channelosome, first of a kind in plants.},
  author       = {Kulich, Ivan and Oulehlová, Denisa and Vladimirtsev, Dmitrii and Zou, Minxia and Lileikyte, Edita and Bondar, Alexey and Kulichová, Katarína and Janda, Martin and Iakovenko, Oksana and Neubergerová, Michaela and Studtrucker, Tanja and Pleskot, Roman and Dietrich, Petra and Fendrych, Matyas and Friml, Jiří},
  booktitle    = {bioRxiv},
  title        = {{Armadillo repeat only proteins are required for the function of plant CNGC channels}},
  doi          = {10.1101/2025.01.06.631460},
  year         = {2025},
}

@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{14447,
  abstract     = {Auxin belongs among major phytohormones and governs multiple aspects of plant growth and development. The establishment of auxin concentration gradients, determines, among other processes, plant organ positioning and growth responses to environmental stimuli.
Herein we report the synthesis of new NBD- or DNS-labelled IAA derivatives and the elucidation of their biological activity, fluorescence properties and subcellular accumulation patterns in planta. These novel compounds did not show auxin-like activity, but instead antagonized physiological auxin effects. The DNS-labelled derivatives FL5 and FL6 showed strong anti-auxin activity in roots and hypocotyls, which also occurred at the level of gene transcription as confirmed by quantitative PCR analysis. The auxin antagonism of our derivatives was further demonstrated in vitro using an SPR-based binding assay. The NBD-labelled compound FL4 with the best fluorescence properties proved to be unsuitable to study auxin accumulation patterns in planta. On the other hand, the strongest anti-auxin activity possessing compounds FL5 and FL6 could be useful to study binding mechanisms to auxin receptors and for manipulations of auxin-regulated processes.},
  author       = {Bieleszová, Kristýna and Hladík, Pavel and Kubala, Martin and Napier, Richard and Brunoni, Federica and Gelová, Zuzana and Fiedler, Lukas and Kulich, Ivan and Strnad, Miroslav and Doležal, Karel and Novák, Ondřej and Friml, Jiří and Žukauskaitė, Asta},
  issn         = {1573-5087},
  journal      = {Plant Growth Regulation},
  pages        = {589--602},
  publisher    = {Springer Nature},
  title        = {{New fluorescent auxin derivatives: Anti-auxin activity and accumulation patterns in Arabidopsis thaliana}},
  doi          = {10.1007/s10725-023-01083-0},
  volume       = {102},
  year         = {2024},
}

@article{15257,
  abstract     = {Root gravitropic bending represents a fundamental aspect of terrestrial plant physiology. Gravity is perceived by sedimentation of starch-rich plastids (statoliths) to the bottom of the central root cap cells. Following gravity perception, intercellular auxin transport is redirected downwards leading to an asymmetric auxin accumulation at the lower root side causing inhibition of cell expansion, ultimately resulting in downwards bending. How gravity-induced statoliths repositioning is translated into asymmetric auxin distribution remains unclear despite PIN auxin efflux carriers and the Negative Gravitropic Response of roots (NGR) proteins polarize along statolith sedimentation, thus providing a plausible mechanism for auxin flow redirection. In this study, using a functional NGR1-GFP construct, we visualized the NGR1 localization on the statolith surface and plasma membrane (PM) domains in close proximity to the statoliths, correlating with their movements. We determined that NGR1 binding to these PM domains is indispensable for NGR1 functionality and relies on cysteine acylation and adjacent polybasic regions as well as on lipid and sterol PM composition. Detailed timing of the early events following graviperception suggested that both NGR1 repolarization and initial auxin asymmetry precede the visible PIN3 polarization. This discrepancy motivated us to unveil a rapid, NGR-dependent translocation of PIN-activating AGCVIII kinase D6PK towards lower PMs of gravity-perceiving cells, thus providing an attractive model for rapid redirection of auxin fluxes following gravistimulation.},
  author       = {Kulich, Ivan and Schmid, Julia and Teplova, Anastasiia and Qi, Linlin and Friml, Jiří},
  issn         = {2050-084X},
  journal      = {eLife},
  keywords     = {General Immunology and Microbiology, General Biochemistry, Genetics and Molecular Biology, General Medicine, General Neuroscience},
  publisher    = {eLife Sciences Publications},
  title        = {{Rapid translocation of NGR proteins driving polarization of PIN-activating D6 protein kinase during root gravitropism}},
  doi          = {10.7554/elife.91523},
  volume       = {12},
  year         = {2024},
}

@article{15319,
  abstract     = {Exocyst component of 70-kDa (EXO70) proteins are constituents of the exocyst complex implicated in vesicle tethering during exocytosis. MILDEW RESISTANCE LOCUS O (MLO) proteins are plant-specific calcium channels and some MLO isoforms enable fungal powdery mildew pathogenesis. We here detected an unexpected phenotypic overlap of Arabidopsis thaliana exo70H4 and mlo2 mlo6 mlo12 triple mutant plants regarding the biogenesis of leaf trichome secondary cell walls. Biochemical and Fourier transform infrared spectroscopic analyses corroborated deficiencies in the composition of trichome cell walls in these mutants. Transgenic lines expressing fluorophore-tagged EXO70H4 and MLO exhibited extensive colocalization of these proteins. Furthermore, mCherry-EXO70H4 mislocalized in trichomes of the mlo triple mutant and, vice versa, MLO6-GFP mislocalized in trichomes of the exo70H4 mutant. Expression of GFP-marked PMR4 callose synthase, a known cargo of EXO70H4-dependent exocytosis, revealed reduced cell wall delivery of GFP-PMR4 in trichomes of mlo triple mutant plants. In vivo protein–protein interaction assays in plant and yeast cells uncovered isoform-preferential interactions between EXO70.2 subfamily members and MLO proteins. Finally, exo70H4 and mlo6 mutants, when combined, showed synergistically enhanced resistance to powdery mildew attack. Taken together, our data point to an isoform-specific interplay of EXO70 and MLO proteins in the modulation of trichome cell wall biogenesis and powdery mildew susceptibility.},
  author       = {Huebbers, Jan W. and Caldarescu, George A. and Kubátová, Zdeňka and Sabol, Peter and Levecque, Sophie C.J. and Kuhn, Hannah and Kulich, Ivan and Reinstädler, Anja and Büttgen, Kim and Manga-Robles, Alba and Mélida, Hugo and Pauly, Markus and Panstruga, Ralph and Žárský, Viktor},
  issn         = {1532-298X},
  journal      = {Plant Cell},
  number       = {4},
  pages        = {1007--1035},
  publisher    = {Oxford University Press},
  title        = {{Interplay of EXO70 and MLO proteins modulates trichome cell wall composition and susceptibility to powdery mildew}},
  doi          = {10.1093/plcell/koad319},
  volume       = {36},
  year         = {2024},
}