TY - THES A1 - Montulet, Orianne T1 - Functional characterization of putative interactors of the Cellulose Synthase Complex T1 - Funktionelle Charakterisierung von mutmaßlichen Interaktoren des Cellulose-Synthase-Komplexes N2 - The plant cell wall plays several crucial roles during plant development with its integrity acting as key signalling component for growth regulation during biotic and abiotic stresses. Cellulose microfibrils, the principal load-bearing components is the major component of the primary cell wall, whose synthesis is mediated by microtubule-associated CELLULOSE SYNTHASE (CESA) COMPLEXES (CSC). Previous studies have shown that CSC interacting proteins COMPANION OF CELLULOSE SYNTHASE (CC) facilitate sustained cellulose synthesis during salt stress by promoting repolymerization of cortical microtubules. However, our understanding of cellulose synthesis during salt stress remains incomplete. In this study, a pull-down of CC1 protein led to the identification of a novel interactor, termed LEA-like. Phylogenetic analysis revealed that LEA-like belongs to the LATE EMBRYOGENESIS ABUNDANT (LEA) protein family, specifically to the LEA_2 subgroup, showing a close relationship with the CC proteins. Roots of the double mutants lea-like and its closest homolog emb3135 exhibited hypersensitivity when grown on cellulose synthesis inhibitors. Further analysis of higher-order mutants of lea-like, emb3135, and cesa6 demonstrated a genetic interaction between them indicating a significant role in cellulose synthesis. Live-cell imaging revealed that both LEA-like and EMB3135 migrated with the CSC at the plasma membrane along microtubule tracks in control and oryzalin-treated conditions which destabilize microtubules, suggesting a tight interaction. Investigation of fluorescently labeled lines of different domains of the LEA-like protein revealed that the N-terminal cytosolic domain of LEA-like colocalizes with microtubules, suggesting a physical association between the two. Considering the established role of LEA proteins in abiotic stress tolerance, we performed phenotypic analysis of the mutant under various stresses. Growth of double mutants of lea-like and emb3135 on NaCl containing media resulted in swelling of root cell indicating a putative role in salt stress tolerance. Supportive of this the quadruple mutant, lacking LEA-like, EMB3135, CC1, and CC2 proteins, exhibited a severe root growth defect on NaCl media compared to control conditions. Live-cell imaging revealed that under salt stress, the LEA-like protein forms aggregates in the plasma membrane. In conclusion, this study has unveiled two novel interactors of the CSC that act with the CC proteins that regulate plant growth in response to salt stress providing new insights into the intricate regulation of cellulose synthesis, particularly under such conditions. N2 - Die pflanzliche Zellwand spielt während der Pflanzenentwicklung mehrere entscheidende Rollen, wobei ihre Integrität als zentrale Signalkomponente für die Wachstumsregulierung bei biotischem und abiotischem Stress fungiert. Zellulose-Mikrofibrillen, die wichtigsten tragenden Komponenten, sind der Hauptbestandteil der primären Zellwand, deren Synthese durch Mikrotubuli assoziierte CELLULOSE SYNTHASE (CESA) Komplexe (CSC) vermittelt wird. Frühere Studien haben gezeigt, dass die mit den CSC interagierenden Proteinen COMPANION OF CELLULOSE SYNTHASE (CC) die anhaltende Zellulosesynthese bei Salzstress erleichtern, indem sie die Repolymerisation der kortikalen Mikrotubuli fördern. Unser Verständnis der Zellulosesynthese bei Salzstress ist jedoch noch unvollständig. In dieser Studie führte ein Pull-down des CC1-Proteins zur Identifizierung eines neuen Interaktors, der als LEA-like bezeichnet wird. Eine phylogenetische Analyse ergab, dass LEA-like zur Late Embryogenesis Abundant (LEA)-Proteinfamilie gehört, insbesondere zur LEA_2-Untergruppe, die eine enge Beziehung zu den CC-Proteinen aufweist. Die Wurzeln der Doppelmutanten lea-like und seines engsten Homologen emb3135 zeigten eine Überempfindlichkeit, wenn sie auf Zellulose-Synthese-Inhibitoren wuchsen. Weitere Analysen von Mutanten höherer Ordnung von lea-like, emb3135 und cesa6 zeigten eine genetische Interaktion zwischen ihnen, die auf eine bedeutende Rolle bei der Zellulosesynthese hinweist. Die Bildgebung in lebenden Zellen zeigte, dass sowohl LEA-like als auch EMB3135 mit dem CSC an der Plasmamembran entlang von Mikrotubuli-Spuren wandern, und zwar sowohl unter Kontrollbedingungen als auch unter Oryzalin-Behandlung, die die Mikrotubuli destabilisiert, was auf eine enge Interaktion hindeutet. Die Untersuchung von fluoreszenzmarkierten Linien verschiedener Domänen des LEA-like-Proteins ergab, dass die N-terminale zytosolische Domäne von LEA-like mit Mikrotubuli kolokalisiert, was auf eine physische Verbindung zwischen den beiden hindeutet. In Anbetracht der bekannten Rolle der LEA-Proteine bei der abiotischen Stresstoleranz haben wir eine phänotypische Analyse der Mutante unter verschiedenen Stressbedingungen durchgeführt. Das Wachstum von Doppelmutanten von lea-like und emb3135 auf NaCl-haltigen Medien führte zu einem Anschwellen der Wurzelzellen, was auf eine mutmaßliche Rolle bei der Salzstresstoleranz hindeutet. Die Vierfachmutante, der die Proteine LEA-like, EMB3135, CC1 und CC2 fehlen, wies im Vergleich zu den Kontrollbedingungen auf NaCl-Medien einen schweren Wachstumsdefekt der Wurzeln auf. Die Bildgebung in lebenden Zellen zeigte, dass das LEA-like-Protein unter Salzstress Aggregate in der Plasmamembran bildet. Zusammenfassend lässt sich sagen, dass diese Studie zwei neue Interaktoren des CSC aufgedeckt hat, die mit den CC-Proteinen zusammenwirken und das Pflanzenwachstum als Reaktion auf Salzstress regulieren. KW - cell wall KW - cellulose KW - salt stress KW - cellulose synthase complex KW - Arabidopsis KW - Zellwand KW - zellulose, Salzstress KW - Cellulose-Synthese-Complex KW - Arabidopsis Y1 - 2024 ER - TY - THES A1 - Wang, Yang T1 - Role of the actin cytoskeleton in cellular morphogenesis at the shoot apical meristem of Arabidopsis thaliana N2 - The morphogenesis of sessile plants is mainly driven by directional cell growth and cell division. The organization of their cytoskeleton and the mechanical properties of the cell wall greatly influence morphogenetic events in plants. It is well known that cortical microtubules (CMTs) contribute to directional growth by regulating the deposition of the cellulose microfibrils, as major cell wall fortifying elements. More recent findings demonstrate that mechanical stresses existing in cells and tissues influence microtubule organization. Also, in dividing cells, mechanical stress directions contribute to the orientation of the new cell wall. In comparison to the microtubule cytoskeleton, the role of the actin cytoskeleton in regulating shoot meristem morphogenesis has not been extensively studied. This thesis focuses on the functional relevance of the actin cytoskeleton during cell and tissue scale morphogenesis in the shoot apical meristem (SAM) of Arabidopsis thaliana. Visualization of transcriptional reporters indicates that ACTIN2 and ACTIN7 are two highly expressed actin genes in the SAM. A link between the actin cytoskeleton and SAM development derives from the observation that the act2-1 act7-1 double mutant has abnormal cell shape and perturbed phyllotactic patterns. Live-cell imaging of the actin cytoskeleton further shows that its organization correlates with cell shape, which indicates a potential role of actin in influencing cellular morphogenesis. In this thesis, a detailed characterization of the act2-1 act7-1 mutant reveals that perturbation of actin leads to more rectangular cellular geometries with more 90° cell internal angles, and higher incidences of four-way junctions (four cell boundaries intersecting together). This observation deviates from the conventional tricellular junctions found in epidermal cells. Quantitative cellular-level growth data indicates that such differences in the act2-1 act7-1 mutant arise due to the reduced accuracy in the placement of the new cell wall, as well as its mechanical maturation. Changes in cellular morphology observed in the act2-1 act7-1 mutant result in cell packing defects that subsequently compromise the flow of information among cells in the SAM. N2 - Die Morphogenese sessiler Pflanzen wird hauptsächlich durch gerichtetes Zellwachstum und Zellteilung angetrieben. Die Organisation des Zytoskeletts und die mechanischen Eigenschaften der Zellwand haben großen Einfluss auf die morphogenetischen Vorgänge in Pflanzen. Es ist bekannt, dass kortikale Mikrotubuli (CMTs) zum gerichteten Wachstum beitragen, indem sie die Bildung von Zellulose-Mikrofibrillen als wichtige Elemente zur Stärkung der Zellwand regulieren. Neuere Erkenntnisse zeigen, dass mechanische Spannungen in den Zellen und Geweben die Organisation der Mikrotubuli beeinflussen. Bei der Zellteilung tragen auch die mechanischen Belastungsrichtungen zur Ausrichtung der neuen Zellwand bei. Im Vergleich zum Zytoskelett der Mikrotubuli ist die Rolle des Aktinzytoskeletts bei der Regulierung der Morphogenese des Sprossmeristems noch nicht umfassend untersucht worden. Diese Arbeit befasst sich mit der funktionellen Bedeutung des Aktinzytoskeletts bei der Zell- und Gewebemorphogenese im Sprossapikalmeristem (SAM) von Arabidopsis thaliana. Die Visualisierung von Transkriptionsreportern zeigt, dass ACTIN2 und ACTIN7 zwei stark exprimierte Aktingene im SAM sind. Eine Verknüpfung zwischen dem Aktinzytoskelett und der Entwicklung des SAMs ergibt sich aus der Beobachtung, dass die act2-1 act7-1 Doppelmutante eine abnorme Zellform und ein gestörtes phyllotaktisches Muster aufweist. Die Lebend-Zell Aufnahmen des Aktinzytoskeletts zeigt außerdem, dass seine Organisation mit der Zellform korreliert, was auf eine mögliche Rolle des Aktins bei der Beeinflussung der zellulären Morphogenese hinweist. In dieser Arbeit wird anhand einer detaillierten Charakterisierung der act2-1 act7-1 Mutante gezeigt, dass eine Störung des Aktins zu rechteckigeren Zellgeometrien mit mehr 90°-Zellinnenwinkeln und einem höheren Vorkommen von Vierfach-Verbindungen (vier sich kreuzende Zellgrenzen) führt. Diese Beobachtung weicht von den konventionellen trizellulären Verbindungen der Epidermiszellen ab. Quantitative Wachstumsdaten auf zellulärer Ebene deuten darauf hin, dass diese Unterschiede in der act2-1 act7-1 Mutante auf die geringere Präzision bei der Platzierung der neuen Zellwand sowie auf ihre mechanische Reifung zurückzuführen sind. Die bei der act2-1 act7-1 Mutante beobachteten Veränderungen der Zellmorphologie führen zu Defekten in der Zellanordnung, die in der weiteren Folge den Informationsfluss zwischen den Zellen im SAM beeinträchtigen. KW - Arabidopsis KW - shoot apical meristem KW - actin KW - cell division KW - cell shape KW - morphogenesis Y1 - 2022 U6 - https://doi.org/10.25932/publishup-55908 ER - TY - JOUR A1 - Singh, Aakanksha A1 - Compart, Julia A1 - AL-Rawi, Shadha Abduljaleel A1 - Mahto, Harendra A1 - Ahmad, Abubakar Musa A1 - Fettke, Jörg T1 - LIKE EARLY STARVATION 1 alters the glucan structures at the starch granule surface and thereby influences the action of both starch-synthesizing and starch-degrading enzymes JF - The plant journal N2 - For starch metabolism to take place correctly, various enzymes and proteins acting on the starch granule surface are crucial. Recently, two non-catalytic starch-binding proteins, pivotal for normal starch turnover in Arabidopsis leaves, namely, EARLY STARVATION 1 (ESV1) and its homolog LIKE EARLY STARVATION 1 (LESV), have been identified. Both share nearly 38% sequence homology. As ESV1 has been found to influence glucan phosphorylation via two starch-related dikinases, alpha-glucan, water dikinase (GWD) and phosphoglucan, water dikinase (PWD), through modulating the surface glucan structures of the starch granules and thus affecting starch degradation, we assess the impact of its homolog LESV on starch metabolism. Thus, the 65-kDa recombinant protein LESV and the 50-kDa ESV1 were analyzed regarding their influence on the action of GWD and PWD on the surface of the starch granules. We included starches from various sources and additionally assessed the effect of these non-enzymatic proteins on other starch-related enzymes, such as starch synthases (SSI and SSIII), starch phosphorylases (PHS1), isoamylase and beta-amylase. The data obtained indicate that starch phosphorylation, hydrolyses and synthesis were affected by LESV and ESV1. Furthermore, incubation with LESV and ESV1 together exerted an additive effect on starch phosphorylation. In addition, a stable alteration of the glucan structures at the starch granule surface following treatment with LESV and ESV1 was observed. Here, we discuss all the observed changes that point to modifications in the glucan structures at the surface of the native starch granules and present a model to explain the existing processes. KW - starch KW - starch metabolism KW - starch surface structure KW - Arabidopsis KW - thaliana Y1 - 2022 U6 - https://doi.org/10.1111/tpj.15855 SN - 0960-7412 SN - 1365-313X VL - 111 IS - 3 SP - 819 EP - 835 PB - Wiley-Blackwell CY - Oxford ER - TY - THES A1 - Spinti, Daniela T1 - Proteasomal protein turnover during defense priming in Arabidopsis T1 - Proteasomaler Proteinabbau während der erworbenen Immunantwort in Arabidopsis N2 - The ubiquitin-proteasome-system (UPS) is a cellular cascade involving three enzymatic steps for protein ubiquitination to target them to the 26S proteasome for proteolytic degradation. Several components of the UPS have been shown to be central for regulation of defense responses during infections with phytopathogenic bacteria. Upon recognition of the pathogen, local defense is induced which also primes the plant to acquire systemic resistance (SAR) for enhanced immune responses upon challenging infections. Here, ubiquitinated proteins were shown to accumulate locally and systemically during infections with Psm and after treatment with the SAR-inducing metabolites salicylic acid (SA) and pipecolic acid (Pip). The role of the 26S proteasome in local defense has been described in several studies, but the potential role during SAR remains elusive and was therefore investigated in this project by characterizing the Arabidopsis proteasome mutants rpt2a-2 and rpn12a-1 during priming and infections with Pseudomonas. Bacterial replication assays reveal decreased basal and systemic immunity in both mutants which was verified on molecular level showing impaired activation of defense- and SAR-genes. rpt2a-2 and rpn12a-1 accumulate wild type like levels of camalexin but less SA. Endogenous SA treatment restores local PR gene expression but does not rescue the SAR-phenotype. An RNAseq experiment of Col-0 and rpt2a-2 reveal weak or absent induction of defense genes in the proteasome mutant during priming. Thus, a functional 26S proteasome was found to be required for induction of SAR while compensatory mechanisms can still be initiated. E3-ubiquitin ligases conduct the last step of substrate ubiquitination and thereby convey specificity to proteasomal protein turnover. Using RNAseq, 11 E3-ligases were found to be differentially expressed during priming in Col-0 of which plant U-box 54 (PUB54) and ariadne 12 (ARI12) were further investigated to gain deeper understanding of their potential role during priming. PUB54 was shown to be expressed during priming and /or triggering with virulent Pseudomonas. pub54 I and pub54-II mutants display local and systemic defense comparable to Col-0. The heavy-metal associated protein 35 (HMP35) was identified as potential substrate of PUB54 in yeast which was verified in vitro and in vivo. PUB54 was shown to be an active E3-ligase exhibiting auto-ubiquitination activity and performing ubiquitination of HMP35. Proteasomal turnover of HMP35 was observed indicating that PUB54 targets HMP35 for ubiquitination and subsequent proteasomal degradation. Furthermore, hmp35-I benefits from increased resistance in bacterial replication assays. Thus, HMP35 is potentially a negative regulator of defense which is targeted and ubiquitinated by PUB54 to regulate downstream defense signaling. ARI12 is transcriptionally activated during priming or triggering and hyperinduced during priming and triggering. Gene expression is not inducible by the defense related hormone salicylic acid (SA) and is dampened in npr1 and fmo1 mutants consequently depending on functional SA- and Pip-pathways, respectively. ARI12 accumulates systemically after priming with SA, Pip or Pseudomonas. ari12 mutants are not altered in resistance but stable overexpression leads to increased resistance in local and systemic tissue. During priming and triggering, unbalanced ARI12 levels (i.e. knock out or overexpression) leads to enhanced FMO1 activation indicating a role of ARI12 in Pip-mediated SAR. ARI12 was shown to be an active E3-ligase with auto-ubiquitination activity likely required for activation with an identified ubiquitination site at K474. Mass spectrometrically identified potential substrates were not verified by additional experiments yet but suggest involvement of ARI12 in regulation of ROS in turn regulating Pip-dependent SAR pathways. Thus, data from this project provide strong indications about the involvement of the 26S proteasome in SAR and identified a central role of the two so far barely described E3-ubiquitin ligases PUB54 and ARI12 as novel components of plant defense. N2 - Das Ubiquitin-Proteasom-System (UPS) ist ein in drei Schritten enzymatisch ablaufender Prozess zur Ubiquitinierung von Proteinen, wodurch diese zum proteolytischen Abbau an das 26S Proteasom geschickt werden. Verschiedene Komponenten des UPS sind zentral an der Regulation von Immunantworten während der Infektion mit phytopathogenen Bakterien beteiligt. Beim Erkennen einer Infektion werden lokale Abwehrreaktionen initiiert, wobei auch mobile Signale in distalen Pflanzenteilen verteilt werden, welche die Pflanze primen (vorbereiten). Mit dem Erwerb der systemischen Resistenz (SAR) kann die Immunantwort bei einer zweiten Infektion verstärkt aktiviert werden. Es wurde hier gezeigt, dass ubiquitinierte Proteine in lokalem und systemischem Gewebe akkumulieren, wenn Arabidopsis mit Pseudomonas infiziert oder mit SAR-induzierender Salizylsäure (SA) oder Pipecolinsäure (Pip) behandelt wird. Die genaue Rolle des 26S Proteasoms in der systemischen Immunantwort ist bisher unklar und wurde daher in diesem Projekt mithilfe der Charakterisierung der Proteasommutanten rpt2a-2 und rpn12a-1 während des Primings genauer untersucht. In Bakterienwachstumsversuchen zeigte sich eine lokal und systemisch erhöhte Suszeptibilität der Proteasommutanten, welche auf molekularer Ebene durch ausbleibende Aktivierung von Abwehrgenen verifiziert wurde. Beide Mutanten akkumulieren ähnliche Mengen Camalexin während einer Infektion, sind aber in der Biosynthese von SA gestört. Die endogene Applikation von SA löst lokale PR-Gen Expression aus, kann aber nicht das SAR-Defizit ausgleichen. In einem RNAseq Experiment wurde das Transkriptom von Col-0 und rpt2a-2 während des Primings analysiert und zeigte, dass zentrale Abwehr- und SAR-Gene nicht oder nur schwach induziert werden. Es konnte somit gezeigt werden, dass ein funktionales 26S Proteasom zur vollen Induktion aller Teile der lokalen und systemischen Immunantwort benötigt wird, während ausgleichende Prozesse weiterhin aktiviert werden können. E3-Ubiquitin Ligasen führen den letzten Schritt der Substratubiquitinierung durch und vermitteln dadurch die Spezifität des proteasomalen Proteinabbaus. Mithilfe des RNAseq Experiments konnten 11 differentiell exprimierte Transkripte, annotiert als E3-Ligasen, identifiziert werden. Von diesen wurden PLANT U-BOX 54 (PUB54) und ARIADNE 12 (ARI12) weiter analysiert, um ein tiefergehendes Verständnis ihres Einflusses auf die systemische Immunantwort zu erhalten. PUB54 wird während des Primings und bei Infektionen mit virulenten Pseudomonas exprimiert. Die pub54 I und pub54-II Mutanten zeigen lokal und systemisch eine wildtyp-ähnliche Resistenz. Das „heavy-metal associated protein 35” (HMP35) wurde in Hefe als potentielles Substrat von PUB54 identifiziert und in vitro und in vivo verifiziert. PUB54 ist eine aktive E3-Ligase mit Autoubiquitinierungsaktivität, welche HMP35 ubiquitiniert. HMP35 wird außerdem in planta proteasomal abgebaut, wodurch eine Ubiquitinierung von HMP35 durch PUB54 zum proteasomalen Abbau nahegelegt wird. Des Weiteren wurde gezeigt, dass hmp35 Mutanten von erhöhter Resistenz profitieren. HMP35 agiert möglicherweise als negativer Regulator der Immunantwort und wird zur Aktivierung von Abwehrreaktionen durch PUB54 für den proteasomalen Abbau markiert. ARI12 wird nach Priming oder Infektion mit Pseudomonas transkriptionell aktiviert und nach sekundärer Infektion hyperinduziert, wobei die Behandlung mit SA keine Expression induziert. ARI12 ist jedoch reduziert in npr1 und fmo1 Mutanten, wodurch eine Abhängigkeit der Genexpression von funktionalen SA- und Pip-Signalwegen angedeutet wird. ARI12 akkumuliert in systemischem Gewebe nach lokaler Behandlung mit SA, Pip, oder Pseudomonas. Die ari12 Mutante zeigt wildtypähnliche Resistenz gegenüber bakteriellen Infektionen, wohingegen die Überexpression zu einer verstärkten Resistenz in lokalem und systemischem Gewebe führt. Unausgewogene Level von ARI12 (d.h. knockout oder Überexpression) führen zur erhöhten Expression von FMO1, sodass ARI12 potentiell eine regulatorische Rolle in der Pip-vermittelten systemischen Immunantwort übernimmt. Es konnte gezeigt werden, dass ARI12 eine aktive E3-Ligase mit Autoubiquitinierungsaktivität an Lys474 ist, welche vermutlich für die Aktivierung benötigt wird. Massenspektrometrisch identifizierte, mögliche Substrate von ARI12 konnten noch nicht experimentell bestätigt werden, deuten aber auf eine Rolle von ARI12 in der Regulation von reaktiven Oxygen Spezies (ROS) hin, welche wiederum Pip-anhängige Signalwege regulieren. Zusammengenommen deuten die Daten aus diesem Projekt darauf hin, dass das 26S Proteasom durch den regulierten Proteinabbau zentral ist für die systemische erworbene Resistenz und dass die bisher wenig untersuchten E3-Ligasen PUB54 und ARI12 neue regulatorische Komponenten der pflanzlichen Immunabwehr darstellen. KW - defense priming KW - Arabidopsis KW - Ubiquitin-proteasome-system KW - E3-ubiquitin ligases KW - Arabidopsis KW - E3-Ubiquitin Ligasen KW - Ubiquitin-Proteasom-System KW - erworbene Immunantwort Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-505909 ER - TY - JOUR A1 - Castellanos, Reynel Urrea A1 - Friedrich, Thomas A1 - Petrovic, Nevena A1 - Altmann, Simone A1 - Brzezinka, Krzysztof A1 - Gorka, Michal A1 - Graf, Alexander A1 - Bäurle, Isabel T1 - FORGETTER2 protein phosphatase and phospholipase D modulate heat stress memory in Arabidopsis JF - The plant journal N2 - Plants can mitigate environmental stress conditions through acclimation. In the case of fluctuating stress conditions such as high temperatures, maintaining a stress memory enables a more efficient response upon recurring stress. In a genetic screen forArabidopsis thalianamutants impaired in the memory of heat stress (HS) we have isolated theFORGETTER2(FGT2) gene, which encodes a type 2C protein phosphatase (PP2C) of the D-clade.Fgt2mutants acquire thermotolerance normally; however, they are defective in the memory of HS. FGT2 interacts with phospholipase D alpha 2 (PLD alpha 2), which is involved in the metabolism of membrane phospholipids and is also required for HS memory. In summary, we have uncovered a previously unknown component of HS memory and identified the FGT2 protein phosphatase and PLD alpha 2 as crucial players, suggesting that phosphatidic acid-dependent signaling or membrane composition dynamics underlie HS memory. KW - priming KW - protein phosphatase KW - stress memory KW - heat stress KW - Arabidopsis KW - thaliana Y1 - 2020 U6 - https://doi.org/10.1111/tpj.14927 SN - 0960-7412 SN - 1365-313X VL - 104 IS - 1 SP - 7 EP - 17 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Olas, Justyna Jadwiga A1 - Wahl, Vanessa T1 - Tissue-specific NIA1 and NIA2 expression in Arabidopsis thaliana JF - Plant Signaling & Behavior N2 - Nitrogen (N) is an essential macronutrient for optimal plant growth and ultimately for crop productivity Nitrate serves as the main N source for most plants. Although it seems a well-established fact that nitrate concentration affects flowering, its molecular mode of action in flowering time regulation was poorly understood. We recently found how nitrate, present at the shoot apical meristem (SAM), controls flowering time In this short communication, we present data on the tissue-specific expression patterns of NITRATE REDUCTASE 1 (NIA1) and NIA2 in planta. We show that transcripts of both genes are present throughout the life cycle of Arabidopsis thaliana plants with NIA1 being predominantly active in leaves and NIA2 in meristematic tissues. KW - Arabidopsis KW - NIA1 KW - NIA2 KW - nitrate assimilation KW - plant development KW - RNA in situ hybridization KW - expression KW - cell KW - and tissue-specificity Y1 - 2019 U6 - https://doi.org/10.1080/15592324.2019.1656035 SN - 1559-2316 SN - 1559-2324 VL - 14 IS - 11 PB - Taylor & Francis Group CY - Philadelphia ER - TY - JOUR A1 - Dong, Yanni A1 - Gupta, Saurabh A1 - Sievers, Rixta A1 - Wargent, Jason J. A1 - Wheeler, David A1 - Putterill, Joanna A1 - Macknight, Richard A1 - Gechev, Tsanko S. A1 - Müller-Röber, Bernd A1 - Dijkwel, Paul P. T1 - Genome draft of the Arabidopsis relative Pachycladon cheesemanii reveals environment JF - BMC genomics N2 - BackgroundPachycladon cheesemanii is a close relative of Arabidopsis thaliana and is an allotetraploid perennial herb which is widespread in the South Island of New Zealand. It grows at altitudes of up to 1000m where it is subject to relatively high levels of ultraviolet (UV)-B radiation. To gain first insights into how Pachycladon copes with UV-B stress, we sequenced its genome and compared the UV-B tolerance of two Pachycladon accessions with those of two A. thaliana accessions from different altitudes.ResultsA high-quality draft genome of P. cheesemanii was assembled with a high percentage of conserved single-copy plant orthologs. Synteny analysis with genomes from other species of the Brassicaceae family found a close phylogenetic relationship of P. cheesemanii with Boechera stricta from Brassicaceae lineage I. While UV-B radiation caused a greater growth reduction in the A. thaliana accessions than in the P. cheesemanii accessions, growth was not reduced in one P. cheesemanii accession. The homologues of A. thaliana UV-B radiation response genes were duplicated in P. cheesemanii, and an expression analysis of those genes indicated that the tolerance mechanism in P. cheesemanii appears to differ from that in A. thaliana.ConclusionAlthough the P. cheesemanii genome shows close similarity with that of A. thaliana, it appears to have evolved novel strategies allowing the plant to tolerate relatively high UV-B radiation. KW - Abiotic stress KW - Arabidopsis KW - Genome assembly KW - Pachycladon KW - UV-B tolerance Y1 - 2019 U6 - https://doi.org/10.1186/s12864-019-6084-4 SN - 1471-2164 VL - 20 IS - 1 PB - BMC CY - London ER - TY - JOUR A1 - Sedaghatmehr, Mastoureh A1 - Thirumalaikumar, Venkatesh P. A1 - Kamranfar, Iman A1 - Marmagne, Anne A1 - Masclaux-Daubresse, Celine A1 - Balazadeh, Salma T1 - A regulatory role of autophagy for resetting the memory of heat stress in plants JF - Plant, cell & environment : cell physiology, whole-plant physiology, community physiology N2 - As sessile life forms, plants are repeatedly confronted with adverse environmental conditions, which can impair development, growth, and reproduction. During evolution, plants have established mechanisms to orchestrate the delicate balance between growth and stress tolerance, to reset cellular biochemistry once stress vanishes, or to keep a molecular memory, which enables survival of a harsher stress that may arise later. Although there are several examples of memory in diverse plants species, the molecular machinery underlying the formation, duration, and resetting of stress memories is largely unknown so far. We report here that autophagy, a central self-degradative process, assists in resetting cellular memory of heat stress (HS) in Arabidopsis thaliana. Autophagy is induced by thermopriming (moderate HS) and, intriguingly, remains high long after stress termination. We demonstrate that autophagy mediates the specific degradation of heat shock proteins at later stages of the thermorecovery phase leading to the accumulation of protein aggregates after the second HS and a compromised heat tolerance. Autophagy mutants retain heat shock proteins longer than wild type and concomitantly display improved thermomemory. Our findings reveal a novel regulatory mechanism for HS memory in plants. KW - Arabidopsis KW - heat shock proteins KW - priming KW - resetting Y1 - 2019 U6 - https://doi.org/10.1111/pce.13426 SN - 0140-7791 SN - 1365-3040 VL - 42 IS - 3 SP - 1054 EP - 1064 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Streubel, Susanna A1 - Fritz, Michael Andre A1 - Teltow, Melanie A1 - Kappel, Christian A1 - Sicard, Adrien T1 - Successive duplication-divergence mechanisms at the RCO locus contributed to leaf shape diversity in the Brassicaceae JF - Development : Company of Biologists N2 - Gene duplication is a major driver for the increase of biological complexity. The divergence of newly duplicated paralogs may allow novel functions to evolve, while maintaining the ancestral one. Alternatively, partitioning the ancestral function among paralogs may allow parts of that role to follow independent evolutionary trajectories. We studied the REDUCED COMPLEXITY (RCO) locus, which contains three paralogs that have evolved through two independent events of gene duplication, and which underlies repeated events of leaf shape evolution within the Brassicaceae. In particular, we took advantage of the presence of three potentially functional paralogs in Capsella to investigate the extent of functional divergence among them. We demonstrate that the RCO copies control growth in different areas of the leaf. Consequently, the copies that are retained active in the different Brassicaceae lineages contribute to define the leaf dissection pattern. Our results further illustrate how successive gene duplication events and subsequent functional divergence can increase trait evolvability by providing independent evolutionary trajectories to specialized functions that have an additive effect on a given trait. KW - Plant development KW - Gene duplication KW - Leaf shape KW - Morphological evolution KW - Capsella KW - Arabidopsis Y1 - 2018 U6 - https://doi.org/10.1242/dev.164301 SN - 0950-1991 SN - 1477-9129 VL - 145 IS - 8 PB - Company of Biologists CY - Cambridge ER - TY - JOUR A1 - Liu, Qinsong A1 - Vain, Thomas A1 - Viotti, Corrado A1 - Doyle, Siamsa M. A1 - Tarkowska, Danuse A1 - Novak, Ondrej A1 - Zipfel, Cyril A1 - Sitbon, Folke A1 - Robert, Stephanie A1 - Hofius, Daniel T1 - Vacuole integrity maintained by DUF300 proteins is required for brassinosteroid signaling regulation JF - Molecular plant N2 - Brassinosteroid (BR) hormone signaling controls multiple processes during plant growth and development and is initiated at the plasma membrane through the receptor kinase BRASSINOSTEROID INSENSITIVE1 (BRI1) together with co-receptors such as BRI1-ASSOCIATED RECEPTOR KINASE1 (BAK1). BRI1 abundance is regulated by endosomal recycling and vacuolar targeting, but the role of vacuole-related proteins in BR receptor dynamics and BR responses remains elusive. Here, we show that the absence of two DUF300 domain-containing tonoplast proteins, LAZARUS1 (LAZ1) and LAZ1 HOMOLOG1 (LAZ1H1), causes vacuole morphology defects, growth inhibition, and constitutive activation of BR signaling. Intriguingly, tonoplast accumulation of BAK1 was substantially increased and appeared causally linked to enhanced BRI1 trafficking and degradation in laz1 laz1h1 plants. Since unrelated vacuole mutants exhibited normal BR responses, our findings indicate that DUF300 proteins play distinct roles in the regulation of BR signaling by maintaining vacuole integrity required to balance subcellular BAK1 pools and BR receptor distribution. KW - brassinosteroid signaling KW - vacuole integrity KW - DUF300 proteins KW - tonoplast KW - Arabidopsis Y1 - 2018 U6 - https://doi.org/10.1016/j.molp.2017.12.015 SN - 1674-2052 SN - 1752-9867 VL - 11 IS - 4 SP - 553 EP - 567 PB - Cell Press CY - Cambridge ER -