@article{15266,
  abstract     = {Plant pathogens often exploit a whole range of effectors to facilitate infection. The RXLR effector AVR1 produced by the oomycete plant pathogen Phytophthora infestans suppresses host defense by targeting Sec5. Sec5 is a subunit of the exocyst, a protein complex that is important for mediating polarized exocytosis during plant development and defense against pathogens. The mechanism by which AVR1 manipulates Sec5 functioning is unknown. In this study, we analyzed the effect of AVR1 on Sec5 localization and functioning in the moss Physcomitrium patens. P. patens has four Sec5 homologs. Two (PpSec5b and PpSec5d) were found to interact with AVR1 in yeast-two-hybrid assays while none of the four showed a positive interaction with AVR1ΔT, a truncated version of AVR1. In P. patens lines carrying β-estradiol inducible AVR1 or AVR1ΔT transgenes, expression of AVR1 or AVR1ΔT caused defects in the development of caulonemal protonema cells and abnormal morphology of chloronema cells. Similar phenotypes were observed in Sec5- or Sec6-silenced P. patens lines, suggesting that both AVR1 and AVR1ΔT affect exocyst functioning in P. patens. With respect to Sec5 localization we found no differences between β-estradiol-treated and untreated transgenic AVR1 lines. Sec5 localizes at the plasma membrane in growing caulonema cells, also during pathogen attack, and its subcellular localization is the same, with or without AVR1 in the vicinity.},
  author       = {Overdijk, Elysa J. R. and Putker, Vera and Smits, Joep and Tang, Han and Bouwmeester, Klaas and Govers, Francine and Ketelaar, Tijs},
  issn         = {1932-6203},
  journal      = {PLoS One},
  keywords     = {Multidisciplinary},
  number       = {4},
  publisher    = {Public Library of Science},
  title        = {{Phytophthora infestans RXLR effector AVR1 disturbs the growth of Physcomitrium patens without affecting Sec5 localization}},
  doi          = {10.1371/journal.pone.0249637},
  volume       = {16},
  year         = {2021},
}

@article{15276,
  abstract     = {Biotrophic plant pathogens secrete effector proteins to manipulate the host physiology. Effectors suppress defenses and induce an environment favorable to disease development. Sequence-based prediction of effector function is impeded by their rapid evolution rate. In the maize pathogen <jats:italic>Ustilago maydis</jats:italic>, effector-coding genes frequently organize in clusters. Here we describe the functional characterization of the <jats:italic>pleiades</jats:italic>, a cluster of ten effector genes, by analyzing the micro- and macroscopic phenotype of the cluster deletion and expressing these proteins <jats:italic>in planta</jats:italic>. Deletion of the <jats:italic>pleiades</jats:italic> leads to strongly impaired virulence and accumulation of reactive oxygen species (ROS) in infected tissue. Eight of the Pleiades suppress the production of ROS upon perception of pathogen associated molecular patterns (PAMPs). Although functionally redundant, the Pleiades target different host components. The paralogs Taygeta1 and Merope1 suppress ROS production in either the cytoplasm or nucleus, respectively. Merope1 targets and promotes the auto-ubiquitination activity of RFI2, a conserved family of E3 ligases that regulates the production of PAMP-triggered ROS burst in plants.},
  author       = {Navarrete, Fernando and Grujic, Nenad and Stirnberg, Alexandra and Saado, Indira and Aleksza, David and Gallei, Michelle C and Adi, Hazem and Alcântara, André and Khan, Mamoona and Bindics, Janos and Trujillo, Marco and Djamei, Armin},
  issn         = {1553-7374},
  journal      = {PLOS Pathogens},
  keywords     = {Virology, Genetics, Molecular Biology, Immunology, Microbiology, Parasitology},
  number       = {6},
  publisher    = {Public Library of Science},
  title        = {{The Pleiades are a cluster of fungal effectors that inhibit host defenses}},
  doi          = {10.1371/journal.ppat.1009641},
  volume       = {17},
  year         = {2021},
}

@article{10223,
  abstract     = {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.},
  author       = {Li, Lanxin and Verstraeten, Inge and Roosjen, Mark and Takahashi, Koji and Rodriguez Solovey, Lesia and Merrin, Jack and Chen, Jian and Shabala, Lana and Smet, Wouter and Ren, Hong and Vanneste, Steffen and Shabala, Sergey and De Rybel, Bert and Weijers, Dolf and Kinoshita, Toshinori and Gray, William M. and Friml, Jiří},
  issn         = {1476-4687},
  journal      = {Nature},
  keywords     = {Multidisciplinary},
  number       = {7884},
  pages        = {273--277},
  publisher    = {Springer Nature},
  title        = {{Cell surface and intracellular auxin signalling for H<sup>+</sup> fluxes in root growth}},
  doi          = {10.1038/s41586-021-04037-6},
  volume       = {599},
  year         = {2021},
}

@inbook{10267,
  abstract     = {Tropisms are among the most important growth responses for plant adaptation to the surrounding environment. One of the most common tropisms is root gravitropism. Root gravitropism enables the plant to anchor securely to the soil enabling the absorption of water and nutrients. Most of the knowledge related to the plant gravitropism has been acquired from the flowering plants, due to limited research in non-seed plants. Limited research on non-seed plants is due in large part to the lack of standard research methods. Here, we describe the experimental methods to evaluate gravitropism in representative non-seed plant species, including the non-vascular plant moss Physcomitrium patens, the early diverging extant vascular plant lycophyte Selaginella moellendorffii and fern Ceratopteris richardii. In addition, we introduce the methods used for statistical analysis of the root gravitropism in non-seed plant species.},
  author       = {Zhang, Yuzhou and Li, Lanxin and Friml, Jiří},
  booktitle    = {Plant Gravitropism},
  editor       = {Blancaflor, Elison B},
  isbn         = {978-1-0716-1676-5},
  pages        = {43--51},
  publisher    = {Springer Nature},
  title        = {{Evaluation of gravitropism in non-seed plants}},
  doi          = {10.1007/978-1-0716-1677-2_2},
  volume       = {2368},
  year         = {2021},
}

@inbook{10268,
  abstract     = {The analysis of dynamic cellular processes such as plant cytokinesis stands and falls with live-cell time-lapse confocal imaging. Conventional approaches to time-lapse imaging of cell division in Arabidopsis root tips are tedious and have low throughput. Here, we describe a protocol for long-term time-lapse simultaneous imaging of multiple root tips on a vertical-stage confocal microscope with automated root tracking. We also provide modifications of the basic protocol to implement this imaging method in the analysis of genetic, pharmacological or laser ablation wounding-mediated experimental manipulations. Our method dramatically improves the efficiency of cell division time-lapse imaging by increasing the throughput, while reducing the person-hour requirements of such experiments.},
  author       = {Hörmayer, Lukas and Friml, Jiří and Glanc, Matous},
  booktitle    = {Plant Cell Division},
  isbn         = {978-1-0716-1743-4},
  issn         = {1940-6029},
  pages        = {105--114},
  publisher    = {Humana Press},
  title        = {{Automated time-lapse imaging and manipulation of cell divisions in Arabidopsis roots by vertical-stage confocal microscopy}},
  doi          = {10.1007/978-1-0716-1744-1_6},
  volume       = {2382},
  year         = {2021},
}

@article{10326,
  abstract     = {Strigolactones (SLs) are carotenoid-derived plant hormones that control shoot branching and communications between host plants and symbiotic fungi or root parasitic plants. Extensive studies have identified the key components participating in SL biosynthesis and signalling, whereas the catabolism or deactivation of endogenous SLs in planta remains largely unknown. Here, we report that the Arabidopsis carboxylesterase 15 (AtCXE15) and its orthologues function as efficient hydrolases of SLs. We show that overexpression of AtCXE15 promotes shoot branching by dampening SL-inhibited axillary bud outgrowth. We further demonstrate that AtCXE15 could bind and efficiently hydrolyse SLs both in vitro and in planta. We also provide evidence that AtCXE15 is capable of catalysing hydrolysis of diverse SL analogues and that such CXE15-dependent catabolism of SLs is evolutionarily conserved in seed plants. These results disclose a catalytic mechanism underlying homoeostatic regulation of SLs in plants, which also provides a rational approach to spatial-temporally manipulate the endogenous SLs and thus architecture of crops and ornamental plants.},
  author       = {Xu, Enjun and Chai, Liang and Zhang, Shiqi and Yu, Ruixue and Zhang, Xixi and Xu, Chongyi and Hu, Yuxin},
  issn         = {2055-0278},
  journal      = {Nature Plants},
  pages        = {1495–1504 },
  publisher    = {Springer Nature},
  title        = {{Catabolism of strigolactones by a carboxylesterase}},
  doi          = {10.1038/s41477-021-01011-y},
  volume       = {7},
  year         = {2021},
}

@article{8582,
  abstract     = {Cell and tissue polarization is fundamental for plant growth and morphogenesis. The polar, cellular localization of Arabidopsis PIN‐FORMED (PIN) proteins is crucial for their function in directional auxin transport. The clustering of PIN polar cargoes within the plasma membrane has been proposed to be important for the maintenance of their polar distribution. However, the more detailed features of PIN clusters and the cellular requirements of cargo clustering remain unclear.
Here, we characterized PIN clusters in detail by means of multiple advanced microscopy and quantification methods, such as 3D quantitative imaging or freeze‐fracture replica labeling. The size and aggregation types of PIN clusters were determined by electron microscopy at the nanometer level at different polar domains and at different developmental stages, revealing a strong preference for clustering at the polar domains.
Pharmacological and genetic studies revealed that PIN clusters depend on phosphoinositol pathways, cytoskeletal structures and specific cell‐wall components as well as connections between the cell wall and the plasma membrane.
This study identifies the role of different cellular processes and structures in polar cargo clustering and provides initial mechanistic insight into the maintenance of polarity in plants and other systems.},
  author       = {Li, Hongjiang and von Wangenheim, Daniel and Zhang, Xixi and Tan, Shutang and Darwish-Miranda, Nasser and Naramoto, Satoshi and Wabnik, Krzysztof T and de Rycke, Riet and Kaufmann, Walter and Gütl, Daniel J and Tejos, Ricardo and Grones, Peter and Ke, Meiyu and Chen, Xu and Dettmer, Jan and Friml, Jiří},
  issn         = {1469-8137},
  journal      = {New Phytologist},
  number       = {1},
  pages        = {351--369},
  publisher    = {Wiley},
  title        = {{Cellular requirements for PIN polar cargo clustering in Arabidopsis thaliana}},
  doi          = {10.1111/nph.16887},
  volume       = {229},
  year         = {2021},
}

@article{8606,
  abstract     = {The leaf is a crucial organ evolved with remarkable morphological diversity to maximize plant photosynthesis. The leaf shape is a key trait that affects photosynthesis, flowering rates, disease resistance, and yield. Although many genes regulating leaf development have been identified in the past years, the precise regulatory architecture underlying the generation of diverse leaf shapes remains to be elucidated. We used cotton as a reference model to probe the genetic framework underlying divergent leaf forms. Comparative transcriptome analysis revealed that the GhARF16‐1 and GhKNOX2‐1 genes might be potential regulators of leaf shape. We functionally characterized the auxin‐responsive factor ARF16‐1 acting upstream of GhKNOX2‐1 to determine leaf morphology in cotton. The transcription of GhARF16‐1 was significantly higher in lobed‐leaved cotton than in smooth‐leaved cotton. Furthermore, the overexpression of GhARF16‐1 led to the upregulation of GhKNOX2‐1 and resulted in more and deeper serrations in cotton leaves, similar to the leaf shape of cotton plants overexpressing GhKNOX2‐1. We found that GhARF16‐1 specifically bound to the promoter of GhKNOX2‐1 to induce its expression. The heterologous expression of GhARF16‐1 and GhKNOX2‐1 in Arabidopsis led to lobed and curly leaves, and a genetic analysis revealed that GhKNOX2‐1 is epistatic to GhARF16‐1 in Arabidopsis, suggesting that the GhARF16‐1 and GhKNOX2‐1 interaction paradigm also functions to regulate leaf shape in Arabidopsis. To our knowledge, our results uncover a novel mechanism by which auxin, through the key component ARF16‐1 and its downstream‐activated gene KNOX2‐1, determines leaf morphology in eudicots.},
  author       = {He, P and Zhang, Yuzhou and Li, H and Fu, X and Shang, H and Zou, C and Friml, Jiří and Xiao, G},
  issn         = {1467-7652},
  journal      = {Plant Biotechnology Journal},
  number       = {3},
  pages        = {548--562},
  publisher    = {Wiley},
  title        = {{GhARF16-1 modulates leaf development by transcriptionally regulating the GhKNOX2-1 gene in cotton}},
  doi          = {10.1111/pbi.13484},
  volume       = {19},
  year         = {2021},
}

@article{8608,
  abstract     = {To adapt to the diverse array of biotic and abiotic cues, plants have evolved sophisticated mechanisms to sense changes in environmental conditions and modulate their growth. Growth-promoting hormones and defence signalling fine tune plant development antagonistically. During host-pathogen interactions, this defence-growth trade-off is mediated by the counteractive effects of the defence hormone salicylic acid (SA) and the growth hormone auxin. Here we revealed an underlying mechanism of SA regulating auxin signalling by constraining the plasma membrane dynamics of PIN2 auxin efflux transporter in Arabidopsis thaliana roots. The lateral diffusion of PIN2 proteins is constrained by SA signalling, during which PIN2 proteins are condensed into hyperclusters depending on REM1.2-mediated nanodomain compartmentalisation. Furthermore, membrane nanodomain compartmentalisation by SA or Remorin (REM) assembly significantly suppressed clathrin-mediated endocytosis. Consequently, SA-induced heterogeneous surface condensation disrupted asymmetric auxin distribution and the resultant gravitropic response. Our results demonstrated a defence-growth trade-off mechanism by which SA signalling crosstalked with auxin transport by concentrating membrane-resident PIN2 into heterogeneous compartments.},
  author       = {Ke, M and Ma, Z and Wang, D and Sun, Y and Wen, C and Huang, D and Chen, Z and Yang, L and Tan, Shutang and Li, R and Friml, Jiří and Miao, Y and Chen, X},
  issn         = {1469-8137},
  journal      = {New Phytologist},
  number       = {2},
  pages        = {963--978},
  publisher    = {Wiley},
  title        = {{Salicylic acid regulates PIN2 auxin transporter hyper-clustering and root gravitropic growth via Remorin-dependent lipid nanodomain organization in Arabidopsis thaliana}},
  doi          = {10.1111/nph.16915},
  volume       = {229},
  year         = {2021},
}

@article{8824,
  abstract     = {Plants are able to orient their growth according to gravity, which ultimately controls both shoot and root architecture.1 Gravitropism is a dynamic process whereby gravistimulation induces the asymmetric distribution of the plant hormone auxin, leading to asymmetric growth, organ bending, and subsequent reset of auxin distribution back to the original pre-gravistimulation situation.1,  2,  3 Differential auxin accumulation during the gravitropic response depends on the activity of polarly localized PIN-FORMED (PIN) auxin-efflux carriers.1,  2,  3,  4 In particular, the timing of this dynamic response is regulated by PIN2,5,6 but the underlying molecular mechanisms are poorly understood. Here, we show that MEMBRANE ASSOCIATED KINASE REGULATOR2 (MAKR2) controls the pace of the root gravitropic response. We found that MAKR2 is required for the PIN2 asymmetry during gravitropism by acting as a negative regulator of the cell-surface signaling mediated by the receptor-like kinase TRANSMEMBRANE KINASE1 (TMK1).2,7,  8,  9,  10 Furthermore, we show that the MAKR2 inhibitory effect on TMK1 signaling is antagonized by auxin itself, which triggers rapid MAKR2 membrane dissociation in a TMK1-dependent manner. Our findings suggest that the timing of the root gravitropic response is orchestrated by the reversible inhibition of the TMK1 signaling pathway at the cell surface.},
  author       = {Marquès-Bueno, MM and Armengot, L and Noack, LC and Bareille, J and Rodriguez Solovey, Lesia and Platre, MP and Bayle, V and Liu, M and Opdenacker, D and Vanneste, S and Möller, BK and Nimchuk, ZL and Beeckman, T and Caño-Delgado, AI and Friml, Jiří and Jaillais, Y},
  issn         = {1879-0445},
  journal      = {Current Biology},
  number       = {1},
  publisher    = {Elsevier},
  title        = {{Auxin-regulated reversible inhibition of TMK1 signaling by MAKR2 modulates the dynamics of root gravitropism}},
  doi          = {10.1016/j.cub.2020.10.011},
  volume       = {31},
  year         = {2021},
}

@article{8992,
  abstract     = {The phytohormone auxin plays a central role in shaping plant growth and development. With decades of genetic and biochemical studies, numerous core molecular components and their networks, underlying auxin biosynthesis, transport, and signaling, have been identified. Notably, protein phosphorylation, catalyzed by kinases and oppositely hydrolyzed by phosphatases, has been emerging to be a crucial type of post-translational modification, regulating physiological and developmental auxin output at all levels. In this review, we comprehensively discuss earlier and recent advances in our understanding of genetics, biochemistry, and cell biology of the kinases and phosphatases participating in auxin action. We provide insights into the mechanisms by which reversible protein phosphorylation defines developmental auxin responses, discuss current challenges, and provide our perspectives on future directions involving the integration of the control of protein phosphorylation into the molecular auxin network.},
  author       = {Tan, Shutang and Luschnig, Christian and Friml, Jiří},
  issn         = {1752-9867},
  journal      = {Molecular Plant},
  number       = {1},
  pages        = {151--165},
  publisher    = {Elsevier},
  title        = {{Pho-view of auxin: Reversible protein phosphorylation in auxin biosynthesis, transport and signaling}},
  doi          = {10.1016/j.molp.2020.11.004},
  volume       = {14},
  year         = {2021},
}

@article{8993,
  abstract     = {N-1-naphthylphthalamic acid (NPA) is a key inhibitor of directional (polar) transport of the hormone auxin in plants. For decades, it has been a pivotal tool in elucidating the unique polar auxin transport-based processes underlying plant growth and development. Its exact mode of action has long been sought after and is still being debated, with prevailing mechanistic schemes describing only indirect connections between NPA and the main transporters responsible for directional transport, namely PIN auxin exporters. Here we present data supporting a model in which NPA associates with PINs in a more direct manner than hitherto postulated. We show that NPA inhibits PIN activity in a heterologous oocyte system and that expression of NPA-sensitive PINs in plant, yeast, and oocyte membranes leads to specific saturable NPA binding. We thus propose that PINs are a bona fide NPA target. This offers a straightforward molecular basis for NPA inhibition of PIN-dependent auxin transport and a logical parsimonious explanation for the known physiological effects of NPA on plant growth, as well as an alternative hypothesis to interpret past and future results. We also introduce PIN dimerization and describe an effect of NPA on this, suggesting that NPA binding could be exploited to gain insights into structural aspects of PINs related to their transport mechanism.},
  author       = {Abas, Lindy and Kolb, Martina and Stadlmann, Johannes and Janacek, Dorina P. and Lukic, Kristina and Schwechheimer, Claus and Sazanov, Leonid A and Mach, Lukas and Friml, Jiří and Hammes, Ulrich Z.},
  issn         = {1091-6490},
  journal      = {Proceedings of the National Academy of Sciences of the United States of America},
  number       = {1},
  publisher    = {National Academy of Sciences},
  title        = {{Naphthylphthalamic acid associates with and inhibits PIN auxin transporters}},
  doi          = {10.1073/pnas.2020857118},
  volume       = {118},
  year         = {2021},
}

@article{9189,
  abstract     = {Transposable elements exist widely throughout plant genomes and play important roles in plant evolution. Auxin is an important regulator that is traditionally associated with root development and drought stress adaptation. The DEEPER ROOTING 1 (DRO1) gene is a key component of rice drought avoidance. Here, we identified a transposon that acts as an autonomous auxin‐responsive promoter and its presence at specific genome positions conveys physiological adaptations related to drought avoidance. Rice varieties with high and auxin‐mediated transcription of DRO1 in the root tip show deeper and longer root phenotypes and are thus better adapted to drought. The INDITTO2 transposon contains an auxin response element and displays auxin‐responsive promoter activity; it is thus able to convey auxin regulation of transcription to genes in its proximity. In the rice Acuce, which displays DRO1‐mediated drought adaptation, the INDITTO2 transposon was found to be inserted at the promoter region of the DRO1 locus. Transgenesis‐based insertion of the INDITTO2 transposon into the DRO1 promoter of the non‐adapted rice variety Nipponbare was sufficient to promote its drought avoidance. Our data identify an example of how transposons can act as promoters and convey hormonal regulation to nearby loci, improving plant fitness in response to different abiotic stresses.},
  author       = {Zhao, Y and Wu, L and Fu, Q and Wang, D and Li, J and Yao, B and Yu, S and Jiang, L and Qian, J and Zhou, X and Han, L and Zhao, S and Ma, C and Zhang, Y and Luo, C and Dong, Q and Li, S and Zhang, L and Jiang, X and Li, Y and Luo, H and Li, K and Yang, J and Luo, Q and Li, L and Peng, S and Huang, H and Zuo, Z and Liu, C and Wang, L and Li, C and He, X and Friml, Jiří and Du, Y},
  issn         = {1365-3040},
  journal      = {Plant, Cell & Environment},
  number       = {6},
  pages        = {1846--1857},
  publisher    = {Wiley},
  title        = {{INDITTO2 transposon conveys auxin-mediated DRO1 transcription for rice drought avoidance}},
  doi          = {10.1111/pce.14029},
  volume       = {44},
  year         = {2021},
}

@article{9254,
  abstract     = {Auxin is a key regulator of plant growth and development. Local auxin biosynthesis and intercellular transport generates regional gradients in the root that are instructive for processes such as specification of developmental zones that maintain root growth and tropic responses. Here we present a toolbox to study auxin-mediated root development that features: (i) the ability to control auxin synthesis with high spatio-temporal resolution and (ii) single-cell nucleus tracking and morphokinetic analysis infrastructure. Integration of these two features enables cutting-edge analysis of root development at single-cell resolution based on morphokinetic parameters under normal growth conditions and during cell-type-specific induction of auxin biosynthesis. We show directional auxin flow in the root and refine the contributions of key players in this process. In addition, we determine the quantitative kinetics of Arabidopsis root meristem skewing, which depends on local auxin gradients but does not require PIN2 and AUX1 auxin transporter activities. Beyond the mechanistic insights into root development, the tools developed here will enable biologists to study kinetics and morphology of various critical processes at the single cell-level in whole organisms.},
  author       = {Hu, Yangjie and Omary, Moutasem and Hu, Yun and Doron, Ohad and Hörmayer, Lukas and Chen, Qingguo and Megides, Or and Chekli, Ori and Ding, Zhaojun and Friml, Jiří and Zhao, Yunde and Tsarfaty, Ilan and Shani, Eilon},
  issn         = {2041-1723},
  journal      = {Nature Communications},
  publisher    = {Springer Nature},
  title        = {{Cell kinetics of auxin transport and activity in Arabidopsis root growth and skewing}},
  doi          = {10.1038/s41467-021-21802-3},
  volume       = {12},
  year         = {2021},
}

@article{9288,
  abstract     = {• The phenylpropanoid pathway serves a central role in plant metabolism, providing numerous compounds involved in diverse physiological processes. Most carbon entering the pathway is incorporated into lignin. Although several phenylpropanoid pathway mutants show seedling growth arrest, the role for lignin in seedling growth and development is unexplored.
• We use complementary pharmacological and genetic approaches to block CINNAMATE‐4‐HYDROXYLASE (C4H) functionality in Arabidopsis seedlings and a set of molecular and biochemical techniques to investigate the underlying phenotypes.
• Blocking C4H resulted in reduced lateral rooting and increased adventitious rooting apically in the hypocotyl. These phenotypes coincided with an inhibition in auxin transport. The upstream accumulation in cis‐cinnamic acid was found to likely cause polar auxin transport inhibition. Conversely, a downstream depletion in lignin perturbed phloem‐mediated auxin transport. Restoring lignin deposition effectively reestablished phloem transport and, accordingly, auxin homeostasis.
• Our results show that the accumulation of bioactive intermediates and depletion in lignin jointly cause the aberrant phenotypes upon blocking C4H, and demonstrate that proper deposition of lignin is essential for the establishment of auxin distribution in seedlings. Our data position the phenylpropanoid pathway and lignin in a new physiological framework, consolidating their importance in plant growth and development.},
  author       = {El Houari, I and Van Beirs, C and Arents, HE and Han, Huibin and Chanoca, A and Opdenacker, D and Pollier, J and Storme, V and Steenackers, W and Quareshy, M and Napier, R and Beeckman, T and Friml, Jiří and De Rybel, B and Boerjan, W and Vanholme, B},
  issn         = {1469-8137},
  journal      = {New Phytologist},
  number       = {6},
  pages        = {2275--2291},
  publisher    = {Wiley},
  title        = {{Seedling developmental defects upon blocking CINNAMATE-4-HYDROXYLASE are caused by perturbations in auxin transport}},
  doi          = {10.1111/nph.17349},
  volume       = {230},
  year         = {2021},
}

@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{9368,
  abstract     = {The quality control system for messenger RNA (mRNA) is fundamental for cellular activities in eukaryotes. To elucidate the molecular mechanism of 3'-Phosphoinositide-Dependent Protein Kinase1 (PDK1), a master regulator that is essential throughout eukaryotic growth and development, we employed a forward genetic approach to screen for suppressors of the loss-of-function T-DNA insertion double mutant pdk1.1 pdk1.2 in Arabidopsis thaliana. Notably, the severe growth attenuation of pdk1.1 pdk1.2 was rescued by sop21 (suppressor of pdk1.1 pdk1.2), which harbours a loss-of-function mutation in PELOTA1 (PEL1). PEL1 is a homologue of mammalian PELOTA and yeast (Saccharomyces cerevisiae) DOM34p, which each form a heterodimeric complex with the GTPase HBS1 (HSP70 SUBFAMILY B SUPPRESSOR1, also called SUPERKILLER PROTEIN7, SKI7), a protein that is responsible for ribosomal rescue and thereby assures the quality and fidelity of mRNA molecules during translation. Genetic analysis further revealed that a dysfunctional PEL1-HBS1 complex failed to degrade the T-DNA-disrupted PDK1 transcripts, which were truncated but functional, and thus rescued the growth and developmental defects of pdk1.1 pdk1.2. Our studies demonstrated the functionality of a homologous PELOTA-HBS1 complex and identified its essential regulatory role in plants, providing insights into the mechanism of mRNA quality control.},
  author       = {Kong, W and Tan, Shutang and Zhao, Q and Lin, DL and Xu, ZH and Friml, Jiří and Xue, HW},
  issn         = {1532-2548},
  journal      = {Plant Physiology},
  number       = {4},
  pages        = {2003--2020},
  publisher    = {American Society of Plant Biologists},
  title        = {{mRNA surveillance complex PELOTA-HBS1 eegulates phosphoinositide-sependent protein kinase1 and plant growth}},
  doi          = {10.1093/plphys/kiab199},
  volume       = {186},
  year         = {2021},
}

@article{9443,
  abstract     = {Endoplasmic reticulum–plasma membrane contact sites (ER–PM CS) play fundamental roles in all eukaryotic cells. Arabidopsis thaliana mutants lacking the ER–PM protein tether synaptotagmin1 (SYT1) exhibit decreased PM integrity under multiple abiotic stresses, such as freezing, high salt, osmotic stress, and mechanical damage. Here, we show that, together with SYT1, the stress-induced SYT3 is an ER–PM tether that also functions in maintaining PM integrity. The ER–PM CS localization of SYT1 and SYT3 is dependent on PM phosphatidylinositol-4-phosphate and is regulated by abiotic stress. Lipidomic analysis revealed that cold stress increased the accumulation of diacylglycerol at the PM in a syt1/3 double mutant relative to wild-type while the levels of most glycerolipid species remain unchanged. In addition, the SYT1-green fluorescent protein fusion preferentially binds diacylglycerol in vivo with little affinity for polar glycerolipids. Our work uncovers a SYT-dependent mechanism of stress adaptation counteracting the detrimental accumulation of diacylglycerol at the PM produced during episodes of abiotic stress.},
  author       = {Ruiz-Lopez, N and Pérez-Sancho, J and Esteban Del Valle, A and Haslam, RP and Vanneste, S and Catalá, R and Perea-Resa, C and Van Damme, D and García-Hernández, S and Albert, A and Vallarino, J and Lin, J and Friml, Jiří and Macho, AP and Salinas, J and Rosado, A and Napier, JA and Amorim-Silva, V and Botella, MA},
  issn         = {1532-298x},
  journal      = {Plant Cell},
  number       = {7},
  pages        = {2431--2453},
  publisher    = {American Society of Plant Biologists},
  title        = {{Synaptotagmins at the endoplasmic reticulum-plasma membrane contact sites maintain diacylglycerol homeostasis during abiotic stress}},
  doi          = {10.1093/plcell/koab122},
  volume       = {33},
  year         = {2021},
}

@article{9656,
  abstract     = {Tropisms, growth responses to environmental stimuli such as light or gravity, are spectacular examples of adaptive plant development. The plant hormone auxin serves as a major coordinative signal. The PIN auxin exporters, through their dynamic polar subcellular localizations, redirect auxin fluxes in response to environmental stimuli and the resulting auxin gradients across organs underly differential cell elongation and bending. In this review, we discuss recent advances concerning regulations of PIN polarity during tropisms, focusing on PIN phosphorylation and trafficking. We also cover how environmental cues regulate PIN actions during tropisms, and a crucial role of auxin feedback on PIN polarity during bending termination. Finally, the interactions between different tropisms are reviewed to understand plant adaptive growth in the natural environment.},
  author       = {Han, Huibin and Adamowski, Maciek and Qi, Linlin and Alotaibi, SS and Friml, Jiří},
  issn         = {1469-8137},
  journal      = {New Phytologist},
  number       = {2},
  pages        = {510--522},
  publisher    = {Wiley},
  title        = {{PIN-mediated polar auxin transport regulations in plant tropic responses}},
  doi          = {10.1111/nph.17617},
  volume       = {232},
  year         = {2021},
}

@article{9657,
  abstract     = {To overcome nitrogen deficiency, legume roots establish symbiotic interactions with nitrogen-fixing rhizobia that is fostered in specialized organs (nodules). Similar to other organs, nodule formation is determined by a local maximum of the phytohormone auxin at the primordium site. However, how auxin regulates nodule development remains poorly understood. Here, we found that in soybean, (Glycine max), dynamic auxin transport driven by PIN-FORMED (PIN) transporter GmPIN1 is involved in nodule primordium formation. GmPIN1 was specifically expressed in nodule primordium cells and GmPIN1 was polarly localized in these cells. Two nodulation regulators, (iso)flavonoids trigger expanded distribution of GmPIN1b to root cortical cells, and cytokinin rearranges GmPIN1b polarity. Gmpin1abc triple mutants generated with CRISPR-Cas9 showed impaired establishment of auxin maxima in nodule meristems and aberrant divisions in the nodule primordium cells. Moreover, overexpression of GmPIN1 suppressed nodule primordium initiation. GmPIN9d, an ortholog of Arabidopsis thaliana PIN2, acts together with GmPIN1 later in nodule development to acropetally transport auxin in vascular bundles, fine-tuning the auxin supply for nodule enlargement. Our findings reveal how PIN-dependent auxin transport modulates different aspects of soybean nodule development and suggest that establishment of auxin gradient is a prerequisite for the proper interaction between legumes and rhizobia.},
  author       = {Gao, Z and Chen, Z and Cui, Y and Ke, M and Xu, H and Xu, Q and Chen, J and Li, Y and Huang, L and Zhao, H and Huang, D and Mai, S and Xu, T and Liu, X and Li, S and Guan, Y and Yang, W and Friml, Jiří and Petrášek, J and Zhang, J and Chen, X},
  issn         = {1532-298x},
  journal      = {Plant Cell},
  number       = {9},
  pages        = {2981–3003},
  publisher    = {American Society of Plant Biologists},
  title        = {{GmPIN-dependent polar auxin transport is involved in soybean nodule development}},
  doi          = {10.1093/plcell/koab183},
  volume       = {33},
  year         = {2021},
}

