Publications by authors named "Markus Geisler"

77 Publications

Was ist wichtiger: grüne oder rote Forschung?

Authors:
Markus Geisler

Biospektrum (Heidelb) 2021 26;27(4):450-451. Epub 2021 Jun 26.

Department Biologie, Universität Fribourg, Route Albert-Gockel 10, CH-1700 Fribourg, Schweiz.

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s12268-021-1604-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8233596PMC
June 2021

A Novel miR167a-OsARF6-OsAUX3 Module Regulates Grain Length and Weight in Rice.

Mol Plant 2021 Jun 26. Epub 2021 Jun 26.

State Key Laboratory of Rice Biology, China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310006, China; Shenzhen Branch, Guangdong Laboratory of Lingnan Modern Agriculture, Genome Analysis Laboratory of the Ministry of Agriculture and Rural Affairs, Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen 518120, China. Electronic address:

Grain size is one of the most import factors of controlling rice yield, as it is associated with grain weight (GW). To date, several rice genes that regulate grain size have been isolated; however, the regulatory mechanism underlying GW control is not fully understood. Herein, a quantitative trait locus qGL5 for grain length (GL) and GW was identified in recombinant inbred lines of 9311 and Nipponbare (NPB), and fine mapped to a candidate gene, OsAUX3. Sequence variations between 9311 and NPB in the OsAUX3 promoter, and loss-of-function of OsAUX3 led to increased GL and GW. RNA-sequencing, gene expression quantification, dual-luciferase reporter assay, chromatin immunoprecipitation-quantitative polymerase chain reaction, and yeast one-hybrid assay demonstrated that OsARF6 is an upstream transcription factor of OsAUX3. OsARF6 directly binds to the auxin response elements of the OsAUX3 promoter, covering a single nucleotide polymorphism site between 9311 and NPB/Dongjin/Hwayoung, thereby controlling GL by altering longitudinal expansion and auxin distribution/content in glume cells. miR167a was also confirmed to positively regulate GL and GW by directing OsARF6 mRNA silencing. Therefore, the miR167a-OsARF6-OsAUX3 module regulates GL and GW in rice, representing a potential target for improving rice yield.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.molp.2021.06.023DOI Listing
June 2021

ABCG transporters export cutin precursors for the formation of the plant cuticle.

Curr Biol 2021 May 22;31(10):2111-2123.e9. Epub 2021 Mar 22.

Department of Plant Molecular Biology, University of Lausanne, 1015 Lausanne, Switzerland. Electronic address:

The plant cuticle is deposited on the surface of primary plant organs, such as leaves, fruits, and floral organs, forming a diffusion barrier and protecting the plant against various abiotic and biotic stresses. Cutin, the structural polyester of the plant cuticle, is synthesized in the apoplast. Plasma-membrane-localized ATP-binding cassette (ABC) transporters of the G family have been hypothesized to export cutin precursors. Here, we characterize SlABCG42 of tomato representing an ortholog of AtABCG32 in Arabidopsis. SlABCG42 expression in Arabidopsis complements the cuticular deficiencies of the Arabidopsis pec1/abcg32 mutant. RNAi-dependent downregulation of both tomato genes encoding proteins highly homologous to AtABCG32 (SlABCG36 and SlABCG42) leads to reduced cutin deposition and formation of a thinner cuticle in tomato fruits. By using a tobacco (Nicotiana benthamiana) protoplast system, we show that AtABCG32 and SlABCG42 have an export activity for 10,16-dihydroxy hexadecanoyl-2-glycerol, a cutin precursor in vivo. Interestingly, also free ω-hydroxy hexadecanoic acid as well as hexadecanedioic acid were exported, furthering the research on the identification of cutin precursors in vivo and the respective mechanisms of their integration into the cutin polymer.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.cub.2021.02.056DOI Listing
May 2021

Early stages of legume-rhizobia symbiosis are controlled by ABCG-mediated transport of active cytokinins.

Nat Plants 2021 04 22;7(4):428-436. Epub 2021 Mar 22.

Department of Plant Molecular Physiology, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznań, Poland.

Growing evidence has highlighted the essential role of plant hormones, notably, cytokinins (CKs), in nitrogen-fixing symbiosis, both at early and late nodulation stages. Despite numerous studies showing the central role of CK in nodulation, the importance of CK transport in the symbiosis is unknown. Here, we show the role of ABCG56, a full-size ATP-binding cassette (ABC) transporter in the early stages of the nodulation. MtABCG56 is expressed in roots and nodules and its messenger RNA levels increase upon treatment with symbiotic bacteria, isolated Nod factor and CKs, accumulating within the epidermis and root cortex. MtABCG56 exports bioactive CKs in an ATP-dependent manner over the plasma membrane and its disruption results in an impairment of nodulation. Our data indicate that ABCG-mediated cytokinin transport is important for proper establishment of N-fixing nodules.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41477-021-00873-6DOI Listing
April 2021

Non-steroidal Anti-inflammatory Drugs Target TWISTED DWARF1-Regulated Actin Dynamics and Auxin Transport-Mediated Plant Development.

Cell Rep 2020 12;33(9):108463

Institute of Science and Technology Austria (IST Austria), Am Campus 1, 3400 Klosterneuburg, Austria. Electronic address:

The widely used non-steroidal anti-inflammatory drugs (NSAIDs) are derivatives of the phytohormone salicylic acid (SA). SA is well known to regulate plant immunity and development, whereas there have been few reports focusing on the effects of NSAIDs in plants. Our studies here reveal that NSAIDs exhibit largely overlapping physiological activities to SA in the model plant Arabidopsis. NSAID treatments lead to shorter and agravitropic primary roots and inhibited lateral root organogenesis. Notably, in addition to the SA-like action, which in roots involves binding to the protein phosphatase 2A (PP2A), NSAIDs also exhibit PP2A-independent effects. Cell biological and biochemical analyses reveal that many NSAIDs bind directly to and inhibit the chaperone activity of TWISTED DWARF1, thereby regulating actin cytoskeleton dynamics and subsequent endosomal trafficking. Our findings uncover an unexpected bioactivity of human pharmaceuticals in plants and provide insights into the molecular mechanism underlying the cellular action of this class of anti-inflammatory compounds.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.celrep.2020.108463DOI Listing
December 2020

A twist in the ABC: regulation of ABC transporter trafficking and transport by FK506-binding proteins.

FEBS Lett 2020 12 13;594(23):3986-4000. Epub 2020 Nov 13.

Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary.

Post-transcriptional regulation of ATP-binding cassette (ABC) proteins has been so far shown to encompass protein phosphorylation, maturation, and ubiquitination. Yet, recent accumulating evidence implicates FK506-binding proteins (FKBPs), a type of peptidylprolyl cis-trans isomerase (PPIase) proteins, in ABC transporter regulation. In this perspective article, we summarize current knowledge on ABC transporter regulation by FKBPs, which seems to be conserved over kingdoms and ABC subfamilies. We uncover striking functional similarities but also differences between regulatory FKBP-ABC modules in plants and mammals. We dissect a PPIase- and HSP90-dependent and independent impact of FKBPs on ABC biogenesis and transport activity. We propose and discuss a putative new mode of transient ABC transporter regulation by cis-trans isomerization of X-prolyl bonds.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/1873-3468.13983DOI Listing
December 2020

Auxin-transporting ABC transporters are defined by a conserved D/E-P motif regulated by a prolylisomerase.

J Biol Chem 2020 09 22;295(37):13094-13105. Epub 2020 Jul 22.

Department of Biology, University of Fribourg, Fribourg, Switzerland. Electronic address:

The plant hormone auxin must be transported throughout plants in a cell-to-cell manner to affect its various physiological functions. ABCB transporters are critical for this polar auxin distribution, but the regulatory mechanisms controlling their function is not fully understood. The auxin transport activity of ABCB1 was suggested to be regulated by a physical interaction with FKBP42/Twisted Dwarf1 (TWD1), a peptidylprolyl isomerase (PPIase), but all attempts to demonstrate such a PPIase activity by TWD1 have failed so far. By using a structure-based approach, we identified several surface-exposed proline residues in the nucleotide binding domain and linker of Arabidopsis ABCB1, mutations of which do not alter ABCB1 protein stability or location but do affect its transport activity. P1008 is part of a conserved signature D/E-P motif that seems to be specific for uxin-ransporting BCBs, which we now refer to as ATAs. Mutation of the acidic residue also abolishes auxin transport activity by ABCB1. All higher plant ABCBs for which auxin transport has been conclusively proven carry this conserved motif, underlining its predictive potential. Introduction of this D/E-P motif into malate importer, ABCB14, increases both its malate and its background auxin transport activity, suggesting that this motif has an impact on transport capacity. The D/E-P1008 motif is also important for ABCB1-TWD1 interactions and activation of ABCB1-mediated auxin transport by TWD1. In summary, our data imply a new function for TWD1 acting as a putative activator of ABCB-mediated auxin transport by isomerization of peptidyl-prolyl bonds.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1074/jbc.RA120.014104DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7489919PMC
September 2020

ABCG36/PEN3/PDR8 Is an Exporter of the Auxin Precursor, Indole-3-Butyric Acid, and Involved in Auxin-Controlled Development.

Front Plant Sci 2019 9;10:899. Epub 2019 Jul 9.

Department of Biology, University of Fribourg, Fribourg, Switzerland.

The PDR-type ABCG transporter, ABCG36/PDR8/PEN3, is thought to be implicated in the export of a few structurally unrelated substrates, including the auxin precursor, indole-3-butyric acid (IBA), although a clear-cut proof of transport is lacking. An outward facing, lateral root (LR) location for ABCG36 fuelled speculations that it might secrete IBA into the rhizosphere. Here, we provide strong evidence that ABCG36 catalyzes the export of IBA - but not of indole-3-acetic acid - through the plasma membrane. ABCG36 seems to function redundantly with the closely related isoform ABCG37/PDR9/PIS1 in a negative control of rootward IBA transport in roots, which might be dampened by concerted, lateral IBA export. Analyses of single and double mutant phenotypes suggest that both ABCG36 and ABCG37 function cooperatively in auxin-controlled plant development. Both seem to possess a dual function in the control of auxin homeostasis in the root tip and long-range transport in the mature root correlating with non-polar and polar expression profiles in the LR cap and epidermis, respectively.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fpls.2019.00899DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6629959PMC
July 2019

HSP90 and co-chaperones: a multitaskers' view on plant hormone biology.

FEBS Lett 2019 07 3;593(13):1415-1430. Epub 2019 Jul 3.

Department of Biology, University of Fribourg, Switzerland.

In order to survive under ever-changing conditions plants must be able to adaptively respond to their environment. Plant hormones and the signaling cross-talk among them play a key role in integrating external and internal cues, enabling the plants to acclimate accordingly. HSP90 and several of its co-chaperones are known as pleiotropic factors involved in the signaling pathways of multiple stress responses, including temperature, drought, and pathogen infection. Recently, hormone receptor components for auxin and jasmonic acid, respectively, have been identified as clients of the HSP90 chaperone system, suggesting a direct HSP90-dependent link to hormone signaling. In this review, we give an overview of the multiple roles of HSP90 and its co-chaperones in plant hormone biology and discuss the largely unexplored targets for signal integration that the activity of these apparent multitaskers may suggest.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/1873-3468.13499DOI Listing
July 2019

A substrate of the ABC transporter PEN3 stimulates bacterial flagellin (flg22)-induced callose deposition in .

J Biol Chem 2019 04 4;294(17):6857-6870. Epub 2019 Mar 4.

From the Department of Stress and Developmental Biology and

Nonhost resistance of against , a filamentous eukaryotic microbe and the causal agent of potato late blight, is based on a multilayered defense system. controls pathogen entry through the penetration-resistance genes and , encoding an atypical myrosinase and an ABC transporter, respectively, required for synthesis and export of unknown indole compounds. To identify pathogen-elicited leaf surface metabolites and further unravel nonhost resistance in , we performed untargeted metabolite profiling by incubating a zoospore suspension on leaves of WT or mutant plants. Among the plant-secreted metabolites, 4-methoxyindol-3-yl-methanol and -(4-methoxy-indol-3-yl-methyl) cysteine were detected in spore suspensions recollected from WT plants, but at reduced levels from the mutant plants. In both whole-cell and microsome-based assays, 4-methoxyindol-3-yl-methanol was transported in a PEN3-dependent manner, suggesting that this compound is a PEN3 substrate. The syntheses of both compounds were dependent on functional PEN2 and phytochelatin synthase 1. None of these compounds inhibited mycelial growth of Of note, exogenous application of 4-methoxyindol-3-yl methanol slightly elevated cytosolic Ca levels and enhanced callose deposition in hydathodes of seedlings treated with a bacterial pathogen-associated molecular pattern (PAMP), flagellin (flg22). Loss of flg22-induced callose deposition in leaves of seedlings was partially reverted by the addition of 4-methoxyindol-3-yl methanol. In conclusion, we have identified a specific indole compound that is a substrate for PEN3 and contributes to the plant defense response against microbial pathogens.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1074/jbc.RA119.007676DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6497936PMC
April 2019

The auxin influx carrier, OsAUX3, regulates rice root development and responses to aluminium stress.

Plant Cell Environ 2019 04 29;42(4):1125-1138. Epub 2018 Nov 29.

State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou, 310058, China.

In rice, there are five members of the auxin carrier AUXIN1/LIKE AUX1 family; however, the biological functions of the other four members besides OsAUX1 remain unknown. Here, by using CRISPR/Cas9, we constructed two independent OsAUX3 knock-down lines, osaux3-1 and osaux3-2, in wild-type rice, Hwayoung (WT/HY) and Dongjin (WT/DJ). osaux3-1 and osaux3-2 have shorter primary roots (PRs), decreased lateral root (LR) density, and longer root hairs (RHs) compared with their WT. OsAUX3 expression in PRs, LRs, and RHs further supports that OsAUX3 plays a critical role in the regulation of root development. OsAUX3 locates at the plasma membrane and functions as an auxin influx carrier affecting acropetal auxin transport. OsAUX3 is up-regulated in the root apex under aluminium (Al) stress, and osaux3-2 is insensitive to Al treatments. Furthermore, 1-naphthylacetic acid accented the sensitivity of WT/DJ and osaux3-2 to respond to Al stress. Auxin concentrations, Al contents, and Al-induced reactive oxygen species-mediated damage in osaux3-2 under Al stress are lower than in WT, indicating that OsAUX3 is involved in Al-induced inhibition of root growth. This study uncovers a novel pathway alleviating Al-induced oxidative damage by inhibition of acropetal auxin transport and provides a new option for engineering Al-tolerant rice species.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/pce.13478DOI Listing
April 2019

A transportome-scale amiRNA-based screen identifies redundant roles of Arabidopsis ABCB6 and ABCB20 in auxin transport.

Nat Commun 2018 10 11;9(1):4204. Epub 2018 Oct 11.

School of Plant Sciences and Food Security, Tel Aviv University, Tel Aviv, 69978, Israel.

Transport of signaling molecules is of major importance for regulating plant growth, development, and responses to the environment. A prime example is the spatial-distribution of auxin, which is regulated via transporters to govern developmental patterning. A critical limitation in our ability to identify transporters by forward genetic screens is their potential functional redundancy. Here, we overcome part of this functional redundancy via a transportome, multi-targeted forward-genetic screen using artificial-microRNAs (amiRNAs). We generate a library of 3000 plant lines expressing 1777 amiRNAs, designed to target closely homologous genes within subclades of transporter families and identify, genotype and quantitatively phenotype, 80 lines showing reproducible shoot growth phenotypes. Within this population, we discover and characterize a strong redundant role for the unstudied ABCB6 and ABCB20 genes in auxin transport and response. The unique multi-targeted lines generated in this study could serve as a genetic resource that is expected to reveal additional transporters.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41467-018-06410-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6182007PMC
October 2018

Seeing is better than believing: visualization of membrane transport in plants.

Authors:
Markus Geisler

Curr Opin Plant Biol 2018 12 22;46:104-112. Epub 2018 Sep 22.

University of Fribourg, Department of Biology, Chemin du Musée 10, CH-1700 Fribourg, Switzerland. Electronic address:

Recently, the plant transport field has shifted their research focus toward a more integrative investigation of transport networks thought to provide the basis for long-range transport routes. Substantial progress was provided by of a series of elegant techniques that allow for a visualization or prediction of substrate movements in plant tissues in contrast to established quantitative methods offering low spatial resolution. These methods are critically evaluated in respect to their spatio-temporal resolution, invasiveness, dynamics and overall quality. Current limitations of transport route predictions-based on transporter locations and transport modeling are addressed. Finally, the potential of new tools that have not yet been fully implemented into plant research is indicated.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.pbi.2018.09.005DOI Listing
December 2018

Tomato ATP-Binding Cassette Transporter SlABCB4 Is Involved in Auxin Transport in the Developing Fruit.

Plants (Basel) 2018 Aug 13;7(3). Epub 2018 Aug 13.

Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya 464-8601, Japan.

Plant ATP binding cassette (ABC) transporters are membrane proteins that are important for transporting a wide range of compounds, including secondary metabolites and phytohormones. In Arabidopsis, some members of the ABCB subfamily of ABC transporter, also known as Multi-Drug Resistance proteins (MDRs), have been implicated in auxin transport. However, reports on the roles of the auxin-mediated ABCBs in fleshy fruit development are rare. Here, we present that SlABCB4, a member of the tomato ABCB subfamily, transports auxin in the developing fruit of tomato. Transient expression of SlABCB4-GFP fusion proteins in tobacco cells showed plasma membrane localization. The transport activity of SlABCB4, expressed in protoplasts, revealed substrate specificity for indole-3-acetic acid export. Gene expression analysis of SlABCB4 revealed high expression levels at the early stages of fruit development. Therefore, SlABCB4 is considered to facilitate auxin distribution in tomato fruit, which is important for tomato fruit development.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/plants7030065DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6161087PMC
August 2018

Arabidopsis BTB/POZ protein-dependent PENETRATION3 trafficking and disease susceptibility.

Nat Plants 2017 Nov 30;3(11):854-858. Epub 2017 Oct 30.

Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, SE-90 187, Umeå, Sweden.

The outermost cell layer of plant roots (epidermis) constantly encounters environmental challenges. The epidermal outer plasma membrane domain harbours the PENETRATION3 (PEN3)/ABCG36/PDR8 ATP-binding cassette transporter that confers non-host resistance to several pathogens. Here, we show that the Arabidopsis ENDOPLASMIC RETICULUM-ARRESTED PEN3 (EAP3) BTB/POZ-domain protein specifically mediates PEN3 exit from the endoplasmic reticulum and confers resistance to a root-penetrating fungus, providing prime evidence for BTB/POZ-domain protein-dependent membrane trafficking underlying disease resistance.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41477-017-0039-zDOI Listing
November 2017

Plant hormone transporters: what we know and what we would like to know.

BMC Biol 2017 10 25;15(1):93. Epub 2017 Oct 25.

Department of Biology, University of Fribourg, 1700, Fribourg, Switzerland.

Hormone transporters are crucial for plant hormone action, which is underlined by severe developmental and physiological impacts caused by their loss-of-function mutations. Here, we summarize recent knowledge on the individual roles of plant hormone transporters in local and long-distance transport. Our inventory reveals that many hormones are transported by members of distinct transporter classes, with an apparent dominance of the ATP-binding cassette (ABC) family and of the Nitrate transport1/Peptide transporter family (NPF). The current need to explore further hormone transporter regulation, their functional interaction, transport directionalities, and substrate specificities is briefly reviewed.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/s12915-017-0443-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5655956PMC
October 2017

A Critical View on ABC Transporters and Their Interacting Partners in Auxin Transport.

Plant Cell Physiol 2017 Oct;58(10):1601-1614

University of Fribourg, Department of Biology, CH-1700 Fribourg, Switzerland.

Different subclasses of ATP-binding cassette (ABC) transporters have been implicated in the transport of native variants of the phytohormone auxin. Here, the putative, individual roles of key members belonging to the ABCB, ABCD and ABCG families, respectively, are highlighted and the knowledge of their assumed expression and transport routes is reviewed and compared with their mutant phenotypes. Protein-protein interactions between ABC transporters and regulatory components during auxin transport are summarized and their importance is critically discussed. There is a focus on the functional interaction between members of the ABCB family and the FKBP42, TWISTED DWARF1, acting as a chaperone during plasma membrane trafficking of ABCBs. Further, the mode and relevance of functional ABCB-PIN interactions is diagnostically re-evaluated. A new nomenclature describing precisely the most likely ABCB-PIN interaction scenarios is suggested. Finally, available tools for the detection and prediction of ABC transporter interactomes are summarized and the potential of future ABC transporter interactome maps is highlighted.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/pcp/pcx104DOI Listing
October 2017

Flavonol-induced changes in PIN2 polarity and auxin transport in the Arabidopsis thaliana rol1-2 mutant require phosphatase activity.

Sci Rep 2017 02 6;7:41906. Epub 2017 Feb 6.

Institute of Plant and Microbial Biology, University of Zurich, Zurich Switzerland.

The phytohormone auxin is a major determinant and regulatory component important for plant development. Auxin transport between cells is mediated by a complex system of transporters such as AUX1/LAX, PIN, and ABCB proteins, and their localization and activity is thought to be influenced by phosphatases and kinases. Flavonols have been shown to alter auxin transport activity and changes in flavonol accumulation in the Arabidopsis thaliana rol1-2 mutant cause defects in auxin transport and seedling development. A new mutation in ROOTS CURL IN NPA 1 (RCN1), encoding a regulatory subunit of the phosphatase PP2A, was found to suppress the growth defects of rol1-2 without changing the flavonol content. rol1-2 rcn1-3 double mutants show wild type-like auxin transport activity while levels of free auxin are not affected by rcn1-3. In the rol1-2 mutant, PIN2 shows a flavonol-induced basal-to-apical shift in polar localization which is reversed in the rol1-2 rcn1-3 to basal localization. In vivo analysis of PINOID action, a kinase known to influence PIN protein localization in a PP2A-antagonistic manner, revealed a negative impact of flavonols on PINOID activity. Together, these data suggest that flavonols affect auxin transport by modifying the antagonistic kinase/phosphatase equilibrium.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/srep41906DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5292950PMC
February 2017

Getting to the Right Side.

Authors:
Markus Geisler

Plant Physiol 2016 Dec;172(4):2081

Department of Biology, University of Fribourg, CH-1700 Fribourg, Switzerland

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1104/pp.16.01728DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5129737PMC
December 2016

SHADE AVOIDANCE 4 Is Required for Proper Auxin Distribution in the Hypocotyl.

Plant Physiol 2017 01 21;173(1):788-800. Epub 2016 Nov 21.

School of Life Sciences, Xiamen Plant Genetics Key Laboratory (Y.G., F.Y., M.W., Y.T.), and State Key Laboratory of Cellular Stress Biology (Y.G., Y.T.), Xiamen University, Xiamen 361102, China;

The phytohormone auxin is involved in virtually every aspect of plant growth and development. Through polar auxin transport, auxin gradients can be established, which then direct plant differentiation and growth. Shade avoidance responses are well-known processes that require polar auxin transport. In this study, we have identified a mutant, shade avoidance 4 (sav4), defective in shade-induced hypocotyl elongation and basipetal auxin transport. SAV4 encodes an unknown protein with armadillo repeat- and tetratricopeptide repeat-like domains known to provide protein-protein interaction surfaces. C terminally yellow fluorescent protein-tagged SAV4 localizes to both the plasma membrane and the nucleus. Membrane-localized SAV4 displays a polar association with the shootward plasma membrane domain in hypocotyl and root cells, which appears to be necessary for its function in hypocotyl elongation. Cotransfection of SAV4 and ATP-binding cassette B1 (ABCB1) auxin transporter in tobacco (Nicotiana benthamiana) revealed that SAV4 blocks ABCB1-mediated auxin efflux. We thus propose that polarly localized SAV4 acts to inhibit ABCB-mediated auxin efflux toward shoots and facilitates the establishment of proper auxin gradients.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1104/pp.16.01491DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5210748PMC
January 2017

Plant development regulated by cytokinin sinks.

Science 2016 09 1;353(6303):1027-1030. Epub 2016 Sep 1.

Zürich-Basel Plant Science Center, Department of Plant and Microbial Biology, University of Zürich, 8008 Zürich, Switzerland.

Morphogenetic signals control the patterning of multicellular organisms. Cytokinins are mobile signals that are perceived by subsets of plant cells. We found that the responses to cytokinin signaling during Arabidopsis development are constrained by the transporter PURINE PERMEASE 14 (PUP14). In our experiments, the expression of PUP14 was inversely correlated to the cytokinin signaling readout. Loss of PUP14 function allowed ectopic cytokinin signaling accompanied by aberrant morphogenesis in embryos, roots, and the shoot apical meristem. PUP14 protein localized to the plasma membrane and imported bioactive cytokinins, thus depleting apoplastic cytokinin pools and inhibiting perception by plasma membrane-localized cytokinin sensors to create a sink for active ligands. We propose that the spatiotemporal cytokinin sink patterns established by PUP14 determine the cytokinin signaling landscape that shapes the morphogenesis of land plants.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1126/science.aaf7254DOI Listing
September 2016

Correction: Learning from each other: ABC transporter regulation by protein phosphorylation in plant and mammalian systems.

Biochem Soc Trans 2016 Apr;44(2):663-73

Department of Biology-Plant Biology, University of Fribourg, Rue Albert Gockel 3, PER04, CH-1700 Fribourg, Switzerland

The ABC (ATP-binding cassette) transporter family in higher plants is highly expanded compared with those of mammalians. Moreover, some members of the plant ABCB subfamily display very high substrate specificity compared with their mammalian counterparts that are often associated with multidrug resistance (MDR) phenomena. In this review we highlight prominent functions of plant and mammalian ABC transporters and summarize our knowledge on their post-transcriptional regulation with a focus on protein phosphorylation. A deeper comparison of regulatory events of human cystic fibrosis transmembrane conductance regulator (CFTR) and ABCB1 from the model plantArabidopsisreveals a surprisingly high degree of similarity. Both physically interact with orthologues of the FK506-binding proteins (FKBPs) that chaperon both transporters to the plasma membrane in an action that seems to involve Hsp90. Further both transporters are phosphorylated at regulatory domains that connect both nucleotide-binding folds. Taken together it appears that ABC transporters exhibit an evolutionary conserved but complex regulation by protein phosphorylation, which apparently is, at least in some cases, tightly connected with protein-protein interactions (PPI).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1042/BST20150128_2DOI Listing
April 2016

TWISTED DWARF1 Mediates the Action of Auxin Transport Inhibitors on Actin Cytoskeleton Dynamics.

Plant Cell 2016 04 6;28(4):930-48. Epub 2016 Apr 6.

Department of Biology, University of Fribourg, CH-1700 Fribourg, Switzerland Department of Plant and Microbial Biology, University of Zurich, CH-8008 Zurich, Switzerland

Plant growth and architecture is regulated by the polar distribution of the hormone auxin. Polarity and flexibility of this process is provided by constant cycling of auxin transporter vesicles along actin filaments, coordinated by a positive auxin-actin feedback loop. Both polar auxin transport and vesicle cycling are inhibited by synthetic auxin transport inhibitors, such as 1-N-naphthylphthalamic acid (NPA), counteracting the effect of auxin; however, underlying targets and mechanisms are unclear. Using NMR, we map the NPA binding surface on the Arabidopsis thaliana ABCB chaperone TWISTED DWARF1 (TWD1). We identify ACTIN7 as a relevant, although likely indirect, TWD1 interactor, and show TWD1-dependent regulation of actin filament organization and dynamics and that TWD1 is required for NPA-mediated actin cytoskeleton remodeling. The TWD1-ACTIN7 axis controls plasma membrane presence of efflux transporters, and as a consequence act7 and twd1 share developmental and physiological phenotypes indicative of defects in auxin transport. These can be phenocopied by NPA treatment or by chemical actin (de)stabilization. We provide evidence that TWD1 determines downstream locations of auxin efflux transporters by adjusting actin filament debundling and dynamizing processes and mediating NPA action on the latter. This function appears to be evolutionary conserved since TWD1 expression in budding yeast alters actin polarization and cell polarity and provides NPA sensitivity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1105/tpc.15.00726DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4863381PMC
April 2016

Master and servant: Regulation of auxin transporters by FKBPs and cyclophilins.

Plant Sci 2016 Apr 16;245:1-10. Epub 2016 Jan 16.

Oregon State University, Department of Botany and Plant Pathology, 2082 Cordley Hall, Corvallis, OR 97331, USA. Electronic address:

Plant development and architecture are greatly influenced by the polar distribution of the essential hormone auxin. The directional influx and efflux of auxin from plant cells depends primarily on AUX1/LAX, PIN, and ABCB/PGP/MDR families of auxin transport proteins. The functional analysis of these proteins has progressed rapidly within the last decade thanks to the establishment of heterologous auxin transport systems. Heterologous co-expression allowed also for the testing of protein-protein interactions involved in the regulation of transporters and identified relationships with members of the FK506-Binding Protein (FKBP) and cyclophilin protein families, which are best known in non-plant systems as cellular receptors for the immunosuppressant drugs, FK506 and cyclosporin A, respectively. Current evidence that such interactions affect membrane trafficking, and potentially the activity of auxin transporters is reviewed. We also propose that FKBPs andcyclophilins might integrate the action of auxin transport inhibitors, such as NPA, on members of the ABCB and PIN family, respectively. Finally, we outline open questions that might be useful for further elucidation of the role of immunophilins as regulators (servants) of auxin transporters (masters).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.plantsci.2015.12.004DOI Listing
April 2016

7-Rhamnosylated Flavonols Modulate Homeostasis of the Plant Hormone Auxin and Affect Plant Development.

J Biol Chem 2016 Mar 7;291(10):5385-95. Epub 2016 Jan 7.

From the Department of Plant and Microbial Biology, University of Zurich, 8008 Zurich, Switzerland,

Flavonols are a group of secondary metabolites that affect diverse cellular processes. They are considered putative negative regulators of the transport of the phytohormone auxin, by which they influence auxin distribution and concomitantly take part in the control of plant organ development. Flavonols are accumulating in a large number of glycosidic forms. Whether these have distinct functions and diverse cellular targets is not well understood. The rol1-2 mutant of Arabidopsis thaliana is characterized by a modified flavonol glycosylation profile that is inducing changes in auxin transport and growth defects in shoot tissues. To determine whether specific flavonol glycosides are responsible for these phenotypes, a suppressor screen was performed on the rol1-2 mutant, resulting in the identification of an allelic series of UGT89C1, a gene encoding a flavonol 7-O-rhamnosyltransferase. A detailed analysis revealed that interfering with flavonol rhamnosylation increases the concentration of auxin precursors and auxin metabolites, whereas auxin transport is not affected. This finding provides an additional level of complexity to the possible ways by which flavonols influence auxin distribution and suggests that flavonol glycosides play an important role in regulating plant development.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1074/jbc.M115.701565DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4777868PMC
March 2016

Learning from each other: ABC transporter regulation by protein phosphorylation in plant and mammalian systems.

Biochem Soc Trans 2015 Oct;43(5):966-74

Department of Biology-Plant Biology, University of Fribourg, Rue Albert Gockel 3, PER04, CH-1700 Fribourg, Switzerland

The ABC (ATP-binding cassette) transporter family in higher plants is highly expanded compared with those of mammalians. Moreover, some members of the plant ABC subfamily B (ABCB) display very high substrate specificity compared with their mammalian counterparts that are often associated with multi-drug resistance phenomena. In this review, we highlight prominent functions of plant and mammalian ABC transporters and summarize our knowledge on their post-transcriptional regulation with a focus on protein phosphorylation. A deeper comparison of regulatory events of human cystic fibrosis transmembrane conductance regulator (CFTR) and ABCB1 from the model plant Arabidopsis reveals a surprisingly high degree of similarity. Both physically interact with orthologues of the FK506-binding proteins that chaperon both transporters to the plasma membrane in an action that seems to involve heat shock protein (Hsp)90. Further, both transporters are phosphorylated at regulatory domains that connect both nt-binding folds. Taken together, it appears that ABC transporters exhibit an evolutionary conserved but complex regulation by protein phosphorylation, which apparently is, at least in some cases, tightly connected with protein-protein interactions (PPI).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1042/BST20150128DOI Listing
October 2015

The auxin transporter, OsAUX1, is involved in primary root and root hair elongation and in Cd stress responses in rice (Oryza sativa L.).

Plant J 2015 Sep 22;83(5):818-30. Epub 2015 Jul 22.

State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou, 310058, China.

Auxin and cadmium (Cd) stress play critical roles during root development. There are only a few reports on the mechanisms by which Cd stress influences auxin homeostasis and affects primary root (PR) and lateral root (LR) development, and almost nothing is known about how auxin and Cd interfere with root hair (RH) development. Here, we characterize rice osaux1 mutants that have a longer PR and shorter RHs in hydroponic culture, and that are more sensitive to Cd stress compared to wild-type (Dongjin). OsAUX1 expression in root hair cells is different from that of its paralogous gene, AtAUX1, which is expressed in non-hair cells. However, OsAUX1, like AtAUX1, localizes at the plasma membrane and appears to function as an auxin tranporter. Decreased auxin distribution and contents in the osaux1 mutant result in reduction of OsCyCB1;1 expression and shortened PRs, LRs and RHs under Cd stress, but may be rescued by treatment with the membrane-permeable auxin 1-naphthalene acetic acid. Treatment with the auxin transport inhibitors 1-naphthoxyacetic acid and N-1-naphthylphthalamic acid increased the Cd sensitivity of WT rice. Cd contents in the osaux1 mutant were not altered, but reactive oxygen species-mediated damage was enhanced, further increasing the sensitivity of the osaux1 mutant to Cd stress. Taken together, our results indicate that OsAUX1 plays an important role in root development and in responses to Cd stress.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/tpj.12929DOI Listing
September 2015

Keeping it all together: auxin-actin crosstalk in plant development.

J Exp Bot 2015 Aug 17;66(16):4983-98. Epub 2015 Jun 17.

University of Fribourg, Department of Biology-Plant Biology, CH-1700 Fribourg, Switzerland

Polar auxin transport and the action of the actin cytoskeleton are tightly interconnected, which is documented by the finding that auxin transporters reach their final destination by active movement of secretory vesicles along F-actin tracks. Moreover, auxin transporter polarity and flexibility is thought to depend on transporter cycling that requires endocytosis and exocytosis of vesicles. In this context, we have reviewed the current literature on an involvement of the actin cytoskeleton in polar auxin transport and identify known similarities and differences in its structure, function and dynamics in comparison to non-plant organisms. By describing how auxin modulates actin expression and actin organization and how actin and its stability affects auxin-transporter endocytosis and recycling, we discuss the current knowledge on regulatory auxin-actin feedback loops. We focus on known effects of auxin and of auxin transport inhibitors on the stability and organization of actin and examine the functionality of auxin and/or auxin transport inhibitor-binding proteins with respect to their suitability to integrate auxin/auxin transport inhibitor action. Finally, we indicate current difficulties in the interpretation of organ, time and concentration-dependent auxin/auxin transport inhibitor treatments and formulate simple future experimental guidelines.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/jxb/erv308DOI Listing
August 2015

Wounding of Arabidopsis halleri leaves enhances cadmium accumulation that acts as a defense against herbivory.

Biometals 2015 Jun 10;28(3):521-8. Epub 2015 Mar 10.

Institute of Plant Biology, University of Zurich, 8008, Zurich, Switzerland.

Approximately 0.2% of all angiosperms are classified as metal hyperaccumulators based on their extraordinarily high leaf metal contents, for example >1% zinc, >0.1% nickel or >0.01% cadmium (Cd) in dry biomass. So far, metal hyperaccumulation has been considered to be a taxon-wide, constitutively expressed trait, the extent of which depends solely on available metal concentrations in the soil. Here we show that in the facultative metallophyte Arabidopsis halleri, both insect herbivory and mechanical wounding of leaves trigger an increase specifically in leaf Cd accumulation. Moreover, the Cd concentrations accumulated in leaves can serve as an elemental defense against herbivory by larvae of the Brassicaceae specialist small white (Pieris rapae), thus allowing the plant to take advantage of this non-essential trace element and toxin. Metal homeostasis genes are overrepresented in the systemic transcriptional response of roots to the wounding of leaves in A. halleri, supporting that leaf Cd accumulation is preceded by systemic signaling events. A similar, but quantitatively less pronounced transcriptional response was observed in A. thaliana, suggesting that the systemically regulated modulation of metal homeostasis in response to leaf wounding also occurs in non-hyperaccumulator plants. This is the first report of an environmental stimulus influencing metal hyperaccumulation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s10534-015-9829-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4427619PMC
June 2015

The cyclophilin A DIAGEOTROPICA gene affects auxin transport in both root and shoot to control lateral root formation.

Development 2015 Feb 23;142(4):712-21. Epub 2015 Jan 23.

University of Fribourg, Department of Biology - Plant Biology, CH-1700 Fribourg, Switzerland.

Cyclophilin A is a conserved peptidyl-prolyl cis-trans isomerase (PPIase) best known as the cellular receptor of the immunosuppressant cyclosporine A. Despite significant effort, evidence of developmental functions of cyclophilin A in non-plant systems has remained obscure. Mutations in a tomato (Solanum lycopersicum) cyclophilin A ortholog, DIAGEOTROPICA (DGT), have been shown to abolish the organogenesis of lateral roots; however, a mechanistic explanation of the phenotype is lacking. Here, we show that the dgt mutant lacks auxin maxima relevant to priming and specification of lateral root founder cells. DGT is expressed in shoot and root, and localizes to both the nucleus and cytoplasm during lateral root organogenesis. Mutation of ENTIRE/IAA9, a member of the auxin-responsive Aux/IAA protein family of transcriptional repressors, partially restores the inability of dgt to initiate lateral root primordia but not the primordia outgrowth. By comparison, grafting of a wild-type scion restores the process of lateral root formation, consistent with participation of a mobile signal. Antibodies do not detect movement of the DGT protein into the dgt rootstock; however, experiments with radiolabeled auxin and an auxin-specific microelectrode demonstrate abnormal auxin fluxes. Functional studies of DGT in heterologous yeast and tobacco-leaf auxin-transport systems demonstrate that DGT negatively regulates PIN-FORMED (PIN) auxin efflux transporters by affecting their plasma membrane localization. Studies in tomato support complex effects of the dgt mutation on PIN expression level, expression domain and plasma membrane localization. Our data demonstrate that DGT regulates auxin transport in lateral root formation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1242/dev.113225DOI Listing
February 2015
-->