Biology subjects

Pencik, A.

Publications and source records attributed to Pencik, A..

17 recordsLinked to original sources

bioRxiv2026

Cytokinin regulates the gravitropic setpoint angle of seminal roots in barley and wheat

Plant root growth angle determines the spatial distribution of roots in soil and thereby influences access to water and nutrients when these resources are heterogeneously distributed. In barley, multiple seminal roots emerge at distinct gravitropic setpoint angles (GSAs) and they reliably re-establish their characteristic growth angles following reorientation, indicating robust intrinsic control. However, the molecular basis underlying GSA variation among roots within a single root system remains unknown. Here, we combined individual root type-specific transcriptomics with laser-capture microdissection to profile gravity-responsive zones (root cap, meristem, and elongation zone). We identified two CYTOKININ OXIDASE/DEHYDROGENASE (CKX) genes whose expression in the root cap was associated with root-specific GSA. Functional analysis showed that ckx mutants, which show higher cytokinin levels, exhibit significantly steeper seminal root GSAs, implicating cytokinin catabolism in root angle regulation. Consistent with this, exogenous cytokinin treatment induced a dose-dependent steepening in root angle in barley. Analyses of gravitropic curvature after gravistimulation further showed that ckx mutants exhibit altered gravitropic responses, indicating that CKX-mediated regulation of the root angle depends on gravity-responsive pathways. Notably, GSA-associated CKX expression patterns and cytokinin-dependent root angle responses were also observed in wheat, suggesting a conservation of this mechanism across cereals. Together, these findings identify cytokinin as a key regulator of root specific setpoint angles within a root system architecture, with potential implications for optimizing crop resource acquisition and yield.

plant biology↗

bioRxiv2026

BpLAZY1A Mediates Transcriptional Polarity and Drives Adaxial Tension Wood Like Tissue Formation in Silver Birch (Betula pendula) Branches

A defining feature of most trees is the architectural distinction between a vertically growing main stem and laterally growing branches. This growth habit increases fitness by increasing photosynthetically active surface area and shading competitors. Here, we studied the weeping birch cultivar Betula pendula Youngii to uncover the mechanisms that maintain lateral branch growth. We identified a loss-of-function mutation in BpLAZY1A, a core component of the gravitropic signalling pathway, as the cause of the weeping phenotype. Forward genetic analysis demonstrated that the weeping phenotype is recessive in silver birch. Transgenic BpLAZY1A RNAi lines phenocopied Youngii, confirming the functional role of BpLAZY1A. Reporter analysis revealed that BpLAZY1A is expressed predominantly in gravity-sensing starch sheath cells, with occasional expression in the main stem phloem. Time lapse imaging revealed two distinct gravitropic responses during branch development - an early response associated with establishment of the branch apex gravitropic set-point angle, and a later response associated with polar reinforcement at the branch base. The main stem retained normal gravitropic responses in BpLAZY1A RNAi lines, indicating a branch-specific role for BpLAZY1A. Integrative analyses combining transcriptomics, chemical profiling, and histochemistry indicated that BpLAZY1A establishes adaxial-abaxial polarity during early branch development. In wild-type branches, pectin-rich tension wood-like tissue formed preferentially in the adaxial xylem, accompanied by adaxial expression of pectin- and tension wood-associated genes, including BpRRT1 and BpCOBRA-LIKE4. Auxin-related genes, including BpIAA29 and BpSAURs, were preferentially upregulated in the abaxial side. This transcriptional asymmetry was reduced in BpLAZY1A RNAi line 1, where tension wood-like tissue formed in both adaxial and abaxial sides of the xylem, indicating a loss of polarity. Together, these findings demonstrate that BpLAZY1A functions specifically in branch gravitropism and links spatially asymmetric gene expression with branch growth orientation and biomechanical reinforcement. Our results identify BpLAZY1A as a key regulator coordinating gravitropic signalling, tissue polarity, and the developmental biomechanics underlying lateral branch growth.

plant biology↗

bioRxiv2026

Wild rice Oryza rufipogon outperforms cultivated rice in stimulating beneficial bacterial endophytes.

Beneficial interactions between plants and microorganisms strongly influence plant health and productivity, and root exudates play a central role in shaping these associations. This study analyzed the transcriptional responses of the bacterial endophytes Enterobacter asburiae RCA24 and Kosakonia sacchari RCA25 to root exudates from two commercial Italian rice accessions (Oryza sativa Baldo and Vialone Nano) and from an accession of the wild progenitor of tropical rice, Oryza rufipogon. Bacterial transcriptome analyses revealed that RCA24 responds differently to O. sativa varieties and that RCA25 was more stimulated by O. rufipogon. Changes in bacterial gene expression were mainly related to central metabolism, stress response, and signal transduction, highlighting a precise pattern of interaction. On the other hand, transcriptome analysis of inoculated rice revealed that RCA24 triggered broader transcriptional changes in plants than RCA25. Differentially expressed genes were related, especially in shoots, to defense responses, hormone-mediated signaling, and ribosome biogenesis, revealing that plants discriminate bacterial strains in a genotype-specific manner at the transcriptional level. Our findings suggest that traits beneficial to plant-soil microbiota interactions present in O. rufipogon and lost during domestication and diversification could be identified and reintroduced into modern rice varieties to improve sustainable field performance through beneficial microbial associations.

plant biology↗

bioRxiv2026

Comprehensive characterisation of IAA inactivation pathways reveals the impact of glycosylation on auxin metabolism and plant development

Together with biosynthesis and transport, inactivation regulates the concentration of indole-3-acetic acid (IAA), a key auxinic compound with a myriad of functions in plant development. Main inactive IAA metabolites are categorised into oxidised forms and ester- or amide-linked conjugates. DIOXYGENASE FOR AUXIN OXIDATION1 (DAO1) and DAO2, 2-oxoglutarate and iron-dependent dioxygenases, contribute to IAA oxidative inactivation in collaboration with group II GRETCHEN HAGEN3 (GH3) IAA-amido synthetases, while a group of UDP-glycosyltransferases (UGTs) conjugate IAA to sugars. To study the IAA inactivation routes, we generated combinatorial mutants between all group II GH3s (gh3oct) and DAO1 or DAO2, as well as between the DAOs and main UGTs. In vivo [13C6]IAA feeding experiments traced the metabolic fate of the exogenously applied IAA, supporting the main IAA inactivation pathway, in which DAO acts downstream of GH3s. They also indicated that UGT-mediated IAA glycosylation is more important than previously assumed for modulating IAA levels and plant development. Our metabolic and transcriptomic data further revealed that gh3oct may still produce some GH3 activity, explaining previous reported phenotypic inconsistencies. Our data additionally suggest that other not yet identified metabolic activities might play a role in IAA overproducing plants, and that the premature downregulation of flowering time integrators like FLOWERING LOCUS C (FLC) likely underlies the early flowering of gh3oct and gh3oct dao1 plants.

plant biology↗

bioRxiv2025

Root growth promotion by Penicillium melinii: mechanistic insights and agricultural applications

O_LIThis study characterizes Penicillium melinii, an endophytic fungus isolated from Arabidopsis thaliana roots, as a plant growth-promoting fungus with potential use as a model to study root development and as a biostimulant for sustainable agriculture. Although endophytes are known to promote plant growth, the underlying molecular mechanisms often remain poorly understood. Here, we aimed to elucidate how P. melinii enhances root system development and to assess its applicability across different crops. C_LIO_LIPhenotypic assays were conducted in Arabidopsis, quinoa and tomato under in vitro, greenhouse and field conditions. Root architecture and biomass were quantified using image-based phenotyping. Transcriptomic and phytohormone profiling assessed plant responses, and fungal genome sequencing coupled with secretome analysis was used to identify candidate effectors and metabolic traits. C_LIO_LIP. melinii consistently promoted root growth and increased plant biomass across species and environments, both in vitro and in the greenhouse. In tomato field trials, this translated into a significant increase in yield. The fungus colonized root surfaces without vascular penetration and triggered a mild transcriptomic response: early activation of stress-response genes followed by their attenuation and sustained upregulation of auxin-related pathways. Notably, the interaction modulates the SLR-ARF-LBD pathway and the number of pre-branch sites probably through increased auxin signalling in the oscillation zone. Additional hormonal changes were limited and mainly associated with the attenuation of the plant response to microorganisms. C_LIO_LIP. melinii enhances lateral root formation through a subtle molecular and metabolic dialogue with the host plant, underscoring its relevance as a model for studying root developmental plasticity. Its strong and reproducible growth-promoting effect, demonstrated with different fungal strains and under controlled and field conditions, supports its potential as a biostimulant for sustainable crop production. C_LI

plant biology↗

bioRxiv2025

Ca2+ signature-dependent control of auxin sensitivity in Arabidopsis

Plants must continually balance growth with arrest, especially under stress. Auxin signaling acts as a central regulatory hub in this process, yet the mechanisms that dynamically tune early auxin signalling in real time remain unknown. Here, we used the light-gated, Ca2+-permeable Channelrhodopsin 2 variant XXM2.0 to optogenetically impose defined Ca2+ signatures on Arabidopsis root cells. Repetitive light activation triggered cytosolic Ca2+ signals that in turn suppressed auxin-induced membrane depolarization and Ca2+ transients. Moreover, prolonged optogenetic Ca2+ stimulation affects auxin-responsive transcriptional reprogramming. As phenotypic output, reversible inhibition of root growth by suppressing cell division and elongation was observed. We further identify a candidate CaM7-CNGC14 module that likely mediates Ca2+-dependent gating of early auxin signalling. Our study thus introduces a synthetic biology approach to decompose calcium-auxin crosstalk in plant cells, and demonstrates that optogenetically imposed cytosolic Ca2+ signals act as dynamic regulators of auxin susceptibility in roots.

plant biology↗

bioRxiv2025

The CYP71A, NIT, AMI, and IAMH gene families are dispensable for indole-3-acetaldoxime-mediated auxin biosynthesis in Arabidopsis

Indole-3-acetic acid (IAA) is a crucial auxin governing plant development and environmental responses. While the indole-3-pyruvic acid (IPyA) pathway is the predominant IAA biosynthesis route, other pathways, like the indole-3-acetaldoxime (IAOx) pathway, have been proposed. The IAOx pathway has garnered attention due to its supposed activation in auxin-overproducing mutants (e.g., sur1, sur2, ugt74b1) and the auxin-like responses triggered by exogenous application of its proposed intermediates: IAOx, indole-3-acetonitrile (IAN), and indole-3-acetamide (IAM). However, despite supporting evidence for individual steps, conclusive physiological relevance of the IAOx pathway remains unproven. Using a comprehensive genetic approach combined with metabolic and phenotypic profiling, we demonstrate that mutating gene families proposed to function in the IAOx pathway does not result in prominent auxin-deficient phenotypes, nor are these genes required for high-auxin production in the sur2 mutant. Our findings also challenge the previously postulated linear IAOx pathway. While exogenously provided IAOx, IAN, and IAM can be converted to IAA in vivo, they do not act as precursors for each other. Finally, our findings question the physiological relevance of IAM and IAN as IAA precursors in plants and suggest the existence of a yet uncharacterized auxin biosynthetic route, likely involving IAOx as an intermediate, for the production of IAA in the sur2 mutant. Future identification of the metabolic steps and the corresponding genes in this new pathway may uncover the previously unknown way of synthesizing IAA in plants.

genetics↗

bioRxiv2024

Long-term high temperatures affect seed maturation and seed coat integrity in Brassica napus

Temperatures above the optimum growth threshold affect seed development, accelerating embryo development and producing seeds with ruptured seed coats. However, the underlying mechanisms of this effect remain unclear. To investigate temperature-induced seed coat rupture, we used a multidisciplinary approach combining detailed phenotyping, transcriptomics, histology, immunolabelling, cell wall profiling and nanoindentation-based mechanics of the seed coat in oilseed rape (Brassica napus). Our data reveal that high temperatures accelerate embryo growth, resulting in larger embryos without a compensatory increase in overall seed size. This rapid embryo expansion may exert elevated mechanical stress on the seed coat cells, significantly thinning the seed coat layers. Concurrently, prolonged exposure to high temperatures drives premature biochemical maturation of the seed coat, characterized by accumulation of demethylesterified pectin. Nanoindentation analysis demonstrated that these changes may have compromised the structural integrity of seed coat cell walls. Ultimately, the weakened seed coat may not withstand the internal tension imposed by the fast-growing embryo, leading to seed coat rupture and reduced seed quality. Our work on seed maturation and the mechanism of heat-induced seed coat rupture provides valuable insights for future research into breeding thermotolerant Brassica napus, crucial in the context of a changing climate. HIGHLIGHTSO_LIGrowth of Brassica napus under long-term high temperatures accelerated embryo growth and led to seed coat rupture in approximately half of the seeds. C_LIO_LIPathways linked to cell wall modification were found to be significantly differentially regulated at high temperatures, accompanied by increased pectin demethylesterification in the seed coat. C_LIO_LIA lower reduced modulus and hardness indicate that the surface of HT seeds is mechanically more compliant and softer. Together with the reduced thickness of the seed coat layers, such a seed coat, as a whole structure, is mechanically weaker and less able to resist deformation imposed by embryo growth, resulting in seed coat rupture. C_LI

plant biology↗

bioRxiv2024

Phenylacetic acid metabolism in land plants: novel pathways and metabolites

In recent years, substantial progress has been made in exploring auxin conjugation and metabolism, primarily aiming at indole-3-acetic acid (IAA). However, the metabolic regulation of another key auxin, phenylacetic acid (PAA), remains largely uncharacterized. Here, we provide a comprehensive exploration of PAA metabolism in land plants. Through LC-MS screening across multiple plant species and their organs, we identified four previously unreported endogenous PAA metabolites: phenylacetyl-leucine (PAA-Leu), phenylacetyl-phenylalanine (PAA-Phe), phenylacetyl-valine (PAA-Val), and phenylacetyl-glucose (PAA-glc). Enzyme assays, genetic evidence, crystal structures, and docking studies demonstrate that PAA and IAA share core metabolic machinery, revealing a complex regulatory network that maintains auxin homeostasis. Furthermore, our study of PAA conjugation with amino acids and glucose suggests limited compensatory mechanisms within known conjugation pathways, pointing to the existence of alternative metabolic routes in land plants. These insights advance our knowledge of auxin-specific metabolic networks and highlight the unique complexity within plant hormone regulation.

plant biology↗

bioRxiv2024

The Draparnaldia genome: alternative mechanisms for multicellularity and terrestrialization in green plants

Green plants contain two algal lineages: Streptophyte algae that diverged into land plants and Chlorophyte algae that are mostly aquatic. Draparnaldia is a Chlorophyte alga morphologically resembling mosses and living in both, the aquatic and terrestrial habitats. Because of its complex morphology and terrestrial adaptations, Draparnaldia can provide new insights into the evolution of multicellularity and terrestrialization in green plants. To develop Draparnaldia into a model, we de novo sequenced its genome and transcriptomes, and profiled its phytohormone repertoire. We found that 1) Expanded gene families in Draparnaldia with respect to unicellular Chlamydomonas are linked to multicellularity and abiotic stresses. 2) Draparnaldias terrestrial adaptations are reflected at both the morphological and molecular levels. 3) Draparnaldia synthesizes most of the phytohormones used by land plants to thrive in terrestrial habitats. All of this makes Draparnaldia a powerful model to uncover and study alternative evolutionary trajectories towards multicellularity and terrestrialization in plants.

evolutionary biology↗

bioRxiv2024

Enhanced auxin signaling hub triggers root hair growth at moderate low temperature in Arabidopsis thaliana

Root hairs (RH) as a mixed tip- and non-tip growing protrusions that develop from root epidermal cells are important for nutrient and water uptake, root anchoring, and interaction with soil microorganisms. Although nutrient availability and temperature are critical interlinked factors for sustained plant growth, the molecular mechanisms underlying their sensing and downstream signaling pathways remain unclear. Here, we identified a moderate low temperature (10{degrees}C) condition that triggers a strong RH elongation response involving several molecular components of the auxin pathway. Then, we have determined that auxin biosynthesis carried out by YUCCAs/TAA1, the auxin transport conducted by PIN2/PIN4 and AUX1/PGP4, and the auxin signaling controlled by TIR1/AFB2 coupled to four specific ARFs (ARF6/ARF8 and ARF7/ARF19), are all crucial for the RH response at moderate low temperature. These results uncover the auxin pathway as one central hub under moderate low temperature in the roots to trigger RH growth. Our work highlights the importance of moderate low temperature stimulus as a complex nutritional signal from the media soil into the roots that may be fine-tuned for future biotechnological applications to enhance nutrient uptake.

plant biology↗

bioRxiv2024

Integration of multi-omics and deep phenotyping provides novel insights into multiple abiotic stress responses in potato

Potato is highly water and space efficient but susceptible to abiotic stresses such as heat, drought, or flooding, which are severely exacerbated by climate change. Understanding of crop acclimation to abiotic stress, however, remains limited. Here, we present a comprehensive molecular and physiological high-throughput profiling of potato (Solanum tuberosum, cv. Desiree) under heat, drought and waterlogging applied as single stresses or in combinations designed to mimic realistic future scenarios. Stress-responses were monitored via daily phenotyping and multi-omics analyses of leaf samples comprising transcriptomics, proteomics, metabolomics and hormonomics at several timepoints during and after stress treatments. Additionally, critical metabolites of tuber samples were analysed at the end of the stress period. Integrative analysis of multi-omics data was performed using a bioinformatic pipeline, which was established here, based on machine learning and knowledge networks. Overall, waterlogging had the most immediate and dramatic effects on potato plants, interestingly activating ABA-responses similar to drought stress. In addition, we observed distinct stress signatures at multiple molecular levels in response to heat or drought and to a combination of both. In response to all treatments, we found a downregulation of photosynthesis at different molecular levels, an accumulation of minor amino acids and diverse stress induced hormones. Our integrative multi-omics analysis provides global insights into plant stress responses, facilitating improved breeding strategies towards climate-adapted potato varieties. One Sentence SummaryIntegrated multi-omics analysis of high-throughput phenotyping in potato reveals distinct molecular signatures of acclimation to single and combined abiotic stresses related to climate change.

plant biology↗

bioRxiv2022

IPT9, a cis-zeatin cytokinin biosynthesis gene, promotes root growth

Cytokinin and auxin are plant hormones that coordinate many aspects of plant development. Their interactions in plant underground growth are well established, occurring at the levels of metabolism, signaling, and transport. Unlike many plant hormone classes, cytokinins are represented by more than one active molecule. Multiple mutant lines, blocking specific parts of cytokinin biosynthetic pathways, have enabled research in plants with deficiencies in specific cytokinin-types. While most of these mutants have confirmed the impeding effect of cytokinin on root growth, the ipt29 double mutant instead surprisingly exhibits reduced primary root length compared to wild type. This mutant is impaired in cis-zeatin (cZ) production, a cytokinin-type that had been considered inactive in the past. Here we have further investigated the intriguing ipt29 root phenotype, opposite to known cytokinin functions, and the (bio)activity of cZ. Our data suggest that despite the ipt29 short-root phenotype, cZ application has a negative impact on primary root growth and can activate a cytokinin response in the stele. Grafting experiments revealed that the root phenotype of ipt29 depends on local signaling which does not relate to directly to cytokinin levels. Notably, ipt29 displayed increased auxin levels in the root tissue. Moreover, analyses of the differential contributions of ipt2 and ipt9 to the ipt29 short-root phenotype demonstrated that, despite its deficiency on cZ levels, ipt2 does not show any root phenotype or auxin homeostasis variation while ipt9 mutants were indistinguishable from ipt29. We conclude that IPT9 functions may go beyond cZ biosynthesis, directly or indirectly, implicating effects on auxin homeostasis and therefore influencing plant growth.

plant biology↗

bioRxiv2021

Inactivation of the entire Arabidopsis group II GH3s confers tolerance to salinity and drought

Indole-3-acetic acid (IAA) controls a plethora of developmental processes. Thus, regulation of their levels is of great relevance for plant performance. Cellular IAA concentration depends on the combined result of its transport, biosynthesis and various redundant pathways to inactivate IAA, including oxidation and conjugation. Group II members of the GRETCHEN HAGEN 3 (GH3) gene family code for acyl acid amido synthetases catalysing the conjugation of IAA to amino acids. However, the high level of functional redundancy among them has hampered thorough analysis of their roles in plant development. In this work, we generated an Arabidopsis gh3.1,2,3,4,5,6,9,17 (gh3oct) mutant to knock-out the group II GH3 pathway. The gh3oct plants had an improved root architecture, were more tolerant to osmotic stresses due to locally increased IAA levels and were more drought tolerant. IAA metabolite quantification in gh3oct plants suggested the existence of additional GH3-like enzymes in IAA metabolism. Moreover, our data suggested that oxIAA production depends, at least partly, on the GH3 pathway. Targeted stress-hormone analysis further suggested an involvement of ABA in the differential response to salinity of gh3oct plants. Taken together, our data provide new insights into the roles of group II GH3s in IAA metabolism and hormone-regulated plant development.

plant biology↗

bioRxiv2021

Effects of long-term high-temperature stress on reproductive growth and seed development in development in Brassica napus

Brassica napus is the second most important oilseed crop worldwide. Increasing average temperatures and extreme weather have a severe impact on rapeseed yield. We determined the response of three cultivars to different temperature regimes (21/18 {degrees}C, 28/18 {degrees}C and 34/18 {degrees}C), focusing on the plant appearance, seed yield, seed quality, seed viability, and embryo development. Our microscopic observations identified that embryo development is affected by high temperatures. We noticed an acceleration of its development, in addition to pattern defects. Reduced fertilization rate, increased abortion rate, and preharvest sprouting would be responsible for the low seed yield at the high-temperature regime. Hormone profiling indicates that reduced auxin levels in young seeds may cause the observed embryo pattern defects. Moreover, reduced seed dormancy may result from low ABA and IAA levels in mature seeds. Glucosinolates and oil composition measurements suggest reduced seed quality. These identified cues help understand seed thermomorphogenesis and pave the way to the development of thermoresilient rapeseed plants. HighlightBrassica napus flowering plants growth at high temperatures accelerates embryo development, causing a high seed abortion rate and reduced seed quality. Temperature-reduced ABA levels cause premature seed sprouting.

plant biology↗

bioRxiv2020

A role of DAO1 in oxidation of IAA amino acid conjugates revealed through metabolite, high throughput transcript and protein level analysis.

Auxin metabolism is, together with auxin transport, a key determinant of auxin signalling output in plant cells, yet details on the underlying mechanisms and factors involved are still largely unknown. Processes involved in the auxin metabolism are subject to regulation based on numerous signals, including auxin concentration itself. Altered auxin availability and the subsequent changes of auxin metabolite profiles can therefore elucidate the function and regulatory role of individual elements in the auxin metabolic machinery. After analysing auxin metabolism in auxin dependent tobacco BY-2 cell line grown in presence or absence of synthetic auxin 2,4-D we found that both conditions were similarly characterized by very low levels of endogenous indole-3-acetic acid (IAA) and its metabolites. However, metabolic profiling after exogenous application of IAA uncovered that the concentration of N-(2-oxindole-3-acetyl)-L-aspartic acid (oxIAA-Asp), the most abundantly formed auxin metabolite in the control culture, dramatically decreased in auxin-starved conditions. To describe the molecular mechanism behind this regulation, we analysed transcriptome and proteome changes caused by auxin starvation. While no changes in the expression of auxin biosynthetic machinery were observed, many genes related to auxin conjugation and degradation showed differential expression. Selected putative auxin glycosylating enzymes as well as members of the Gretchen Hagen 3 gene family involved in auxin amino acid conjugation showed both up- and down-regulation. Contrarily to that, all tobacco homologs of Arabidopsis thaliana DIOXYGENASE FOR AUXIN OXIDATION 1 (DAO1), known to be responsible for the formation of oxIAA from IAA, showed significant downregulation at both transcript and protein levels. To validate the role of DAO1 in auxin metabolism, we performed auxin metabolite profiling in BY-2 mutants carrying either siRNA-silenced or CRISPR-Cas9-mutated NtDAO1, as well as in dao1-1 Arabidopsis thaliana plants. Both mutants showed not only expectedly lower levels of oxIAA, but also significantly lower abundance of oxidated amino acid conjugates of IAA (oxIAA-Asp). Our results thus represent the first direct evidence on DAO1 activity on IAA amino acid conjugates. Statement of significanceHere we present an analysis of auxin metabolism on metabolite, transcript and protein levels in tobacco BY-2 cell line, collectively identifying oxidation of IAA amino acid conjugates as a new role of DIOXYGENASE FOR AUXIN OXIDATION 1 within an auxin-level-responsive metabolic system.

plant biology↗

bioRxiv2018

Anthranilic acid regulates subcellular localization of auxin transporters during root gravitropism

O_LIDistribution of auxin within plant tissues is of great importance for developmental plasticity, including root gravitropic growth. Auxin flow is directed by the subcellular polar distribution and dynamic relocalization of auxin transporters such as the PIN-FORMED (PIN) efflux carriers, which can be influenced by the main natural plant auxin indole-3-acetic acid (IAA). Anthranilic acid (AA) is an important early precursor of IAA and previously published studies with AA analogues suggested that AA may also regulate PIN localization.\nC_LIO_LIUsing Arabidopsis thaliana as a model species, we studied an AA-deficient mutant displaying agravitropic root growth, treated seedlings with AA and AA analogues and transformed lines to over-produce AA while inhibiting its conversion to downstream IAA precursors.\nC_LIO_LIWe showed that AA rescues root gravitropic growth in the AA-deficient mutant at concentrations that do not rescue IAA levels. Overproduction of AA affects root gravitropism without affecting IAA levels. Treatments with, or deficiency in, AA result in defects in PIN polarity and gravistimulus-induced PIN relocalization in root cells.\nC_LIO_LIOur results reveal a previously unknown role for AA in the regulation of PIN subcellular localization and dynamics involved in root gravitropism, which is independent of its better-known role in IAA biosynthesis.\nC_LI

plant biology↗