TY - JOUR A1 - Lehmann, Julian A1 - Jørgensen, Morten E. A1 - Fratz, Stefanie A1 - Müller, Heike M. A1 - Kusch, Jana A1 - Scherzer, Sönke A1 - Navarro-Retamal, Carlos A1 - Mayer, Dominik A1 - Böhm, Jennifer A1 - Konrad, Kai R. A1 - Terpitz, Ulrich A1 - Dreyer, Ingo A1 - Mueller, Thomas D. A1 - Sauer, Markus A1 - Hedrich, Rainer A1 - Geiger, Dietmar A1 - Maierhofer, Tobias T1 - Acidosis-induced activation of anion channel SLAH3 in the flooding-related stress response of Arabidopsis JF - Current Biology N2 - Plants, as sessile organisms, gained the ability to sense and respond to biotic and abiotic stressors to survive severe changes in their environments. The change in our climate comes with extreme dry periods but also episodes of flooding. The latter stress condition causes anaerobiosis-triggered cytosolic acidosis and impairs plant function. The molecular mechanism that enables plant cells to sense acidity and convey this signal via membrane depolarization was previously unknown. Here, we show that acidosis-induced anion efflux from Arabidopsis (Arabidopsis thaliana) roots is dependent on the S-type anion channel AtSLAH3. Heterologous expression of SLAH3 in Xenopus oocytes revealed that the anion channel is directly activated by a small, physiological drop in cytosolic pH. Acidosis-triggered activation of SLAH3 is mediated by protonation of histidine 330 and 454. Super-resolution microscopy analysis showed that the increase in cellular proton concentration switches SLAH3 from an electrically silent channel dimer into its active monomeric form. Our results show that, upon acidification, protons directly switch SLAH3 to its open configuration, bypassing kinase-dependent activation. Moreover, under flooding conditions, the stress response of Arabidopsis wild-type (WT) plants was significantly higher compared to SLAH3 loss-of-function mutants. Our genetic evidence of SLAH3 pH sensor function may guide the development of crop varieties with improved stress tolerance. KW - SLAH3 KW - S-type anion channel KW - hypoxia KW - pH KW - cytosolic acidification KW - flooding KW - PALM KW - stoichiometry Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-363320 VL - 31 ER - TY - JOUR A1 - Huang, Shouguang A1 - Waadt, Rainer A1 - Nuhkat, Maris A1 - Kollist, Hannes A1 - Hedrich, Rainer A1 - Roelfsema, M. Rob G. T1 - Calcium signals in guard cells enhance the efficiency by which abscisic acid triggers stomatal closure JF - New Phytologist N2 - During drought, abscisic acid (ABA) induces closure of stomata via a signaling pathway that involves the calcium (Ca2+)-independent protein kinase OST1, as well as Ca2+-dependent protein kinases. However, the interconnection between OST1 and Ca2+ signaling in ABA-induced stomatal closure has not been fully resolved. ABA-induced Ca2+ signals were monitored in intact Arabidopsis leaves, which express the ratiometric Ca2+ reporter R-GECO1-mTurquoise and the Ca2+-dependent activation of S-type anion channels was recorded with intracellular double-barreled microelectrodes. ABA triggered Ca2+ signals that occurred during the initiation period, as well as in the acceleration phase of stomatal closure. However, a subset of stomata closed in the absence of Ca2+ signals. On average, stomata closed faster if Ca2+ signals were elicited during the ABA response. Loss of OST1 prevented ABA-induced stomatal closure and repressed Ca2+ signals, whereas elevation of the cytosolic Ca2+ concentration caused a rapid activation of SLAC1 and SLAH3 anion channels. Our data show that the majority of Ca2+ signals are evoked during the acceleration phase of stomatal closure, which is initiated by OST1. These Ca2+ signals are likely to activate Ca2+-dependent protein kinases, which enhance the activity of S-type anion channels and boost stomatal closure. KW - abscisic acid (ABA) KW - Ca2+- indicator KW - cytosolic Ca2+ signals KW - OST1 protein kinase KW - R-GECO1-mTurquoise KW - SLAC1 and SLAH3 anion channels KW - stomata Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-322716 VL - 224 ER - TY - JOUR A1 - Wan, Wei-Lin A1 - Zhang, Lisha A1 - Pruitt, Rory A1 - Zaidem, Maricris A1 - Brugman, Rik A1 - Ma, Xiyu A1 - Krol, Elzbieta A1 - Perraki, Artemis A1 - Kilian, Joachim A1 - Grossmann, Guido A1 - Stahl, Mark A1 - Shan, Libo A1 - Zipfel, Cyril A1 - van Kan, Jan A. L. A1 - Hedrich, Rainer A1 - Weigel, Detlef A1 - Gust, Andrea A. A1 - Nürnberger, Thorsten T1 - Comparing Arabidopsis receptor kinase and receptor protein-mediated immune signaling reveals BIK1-dependent differences JF - New Phytologist N2 - Pattern recognition receptors (PRRs) sense microbial patterns and activate innate immunity against attempted microbial invasions. The leucine-rich repeat receptor kinases (LRR-RK) FLS2 and EFR, and the LRR receptor protein (LRR-RP) receptors RLP23 and RLP42, respectively, represent prototypical members of these two prominent and closely related PRR families. We conducted a survey of Arabidopsis thaliana immune signaling mediated by these receptors to address the question of commonalities and differences between LRR-RK and LRR-RP signaling. Quantitative differences in timing and amplitude were observed for several early immune responses, with RP-mediated responses typically being slower and more prolonged than those mediated by RKs. Activation of RLP23, but not FLS2, induced the production of camalexin. Transcriptomic analysis revealed that RLP23-regulated genes represent only a fraction of those genes differentially expressed upon FLS2 activation. Several positive and negative regulators of FLS2-signaling play similar roles in RLP23 signaling. Intriguingly, the cytoplasmic receptor kinase BIK1, a positive regulator of RK signaling, acts as a negative regulator of RP-type immune receptors in a manner dependent on BIK1 kinase activity. Our study unveiled unexpected differences in two closely related receptor systems and reports a new negative role of BIK1 in plant immunity. KW - Arabidopsis KW - immune receptor KW - immune signaling comparison KW - plant immunity KW - receptor kinase KW - receptor protein Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-233385 VL - 221 ER - TY - JOUR A1 - Graus, Dorothea A1 - Konrad, Kai R. A1 - Bemm, Felix A1 - Nebioglu, Meliha Görkem Patir A1 - Lorey, Christian A1 - Duscha, Kerstin A1 - Güthoff, Tilman A1 - Herrmann, Johannes A1 - Ferjani, Ali A1 - Cuin, Tracey Ann A1 - Roelfsema, M. Rob G. A1 - Schumacher, Karin A1 - Neuhaus, H. Ekkehard A1 - Marten, Irene A1 - Hedrich, Rainer T1 - High V-PPase activity is beneficial under high salt loads, but detrimental without salinity JF - New Phytologist N2 - The membrane-bound proton-pumping pyrophosphatase (V-PPase), together with the V-type H+-ATPase, generates the proton motive force that drives vacuolar membrane solute transport. Transgenic plants constitutively overexpressing V-PPases were shown to have improved salinity tolerance, but the relative impact of increasing PPi hydrolysis and proton-pumping functions has yet to be dissected. For a better understanding of the molecular processes underlying V-PPase-dependent salt tolerance, we transiently overexpressed the pyrophosphate-driven proton pump (NbVHP) in Nicotiana benthamiana leaves and studied its functional properties in relation to salt treatment by primarily using patch-clamp, impalement electrodes and pH imaging. NbVHP overexpression led to higher vacuolar proton currents and vacuolar acidification. After 3 d in salt-untreated conditions, V-PPase-overexpressing leaves showed a drop in photosynthetic capacity, plasma membrane depolarization and eventual leaf necrosis. Salt, however, rescued NbVHP-hyperactive cells from cell death. Furthermore, a salt-induced rise in V-PPase but not of V-ATPase pump currents was detected in nontransformed plants. The results indicate that under normal growth conditions, plants need to regulate the V-PPase pump activity to avoid hyperactivity and its negative feedback on cell viability. Nonetheless, V-PPase proton pump function becomes increasingly important under salt stress for generating the pH gradient necessary for vacuolar proton-coupled Na+ sequestration. KW - cell death KW - plasma membrane voltage KW - proton pump currents KW - salt KW - vacuolar pH KW - vacuolar proton-ATPase (V-ATPase) KW - vacuolar proton-pyrophosphatase (V-PPase) Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-227553 VL - 219 ER - TY - JOUR A1 - Voss, Lena J. A1 - McAdam, Scott A. M. A1 - Knoblauch, Michael A1 - Rathje, Jan M. A1 - Brodribb, Tim A1 - Hedrich, Rainer A1 - Roelfsema, M. Rob G. T1 - Guard cells in fern stomata are connected by plasmodesmata, but control cytosolic Ca2+ levels autonomously JF - New Phytologist N2 - Recent studies have revealed that some responses of fern stomata to environmental signals differ from those of their relatives in seed plants. However, it is unknown whether the biophysical properties of guard cells differ fundamentally between species of both clades. Intracellular micro-electrodes and the fluorescent Ca2+ reporter FURA2 were used to study voltage-dependent cation channels and Ca2+ signals in guard cells of the ferns Polypodium vulgare and Asplenium scolopendrium. Voltage clamp experiments with fern guard cells revealed similar properties of voltage-dependent K+ channels as found in seed plants. However, fluorescent dyes moved within the fern stomata, from one guard cell to the other, which does not occur in most seed plants. Despite the presence of plasmodesmata, which interconnect fern guard cells, Ca2+ signals could be elicited in each of the cells individually. Based on the common properties of voltage-dependent channels in ferns and seed plants, it is likely that these key transport proteins are conserved in vascular plants. However, the symplastic connections between fern guard cells in mature stomata indicate that the biophysical mechanisms that control stomatal movements differ between ferns and seed plants. KW - calcium signals KW - ferns KW - guard cell KW - plasmodesmata KW - potassium channels KW - seed plants KW - stomata Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-233247 VL - 219 ER - TY - JOUR A1 - Hedrich, Rainer A1 - Mueller, Thomas D. A1 - Becker, Dirk A1 - Marten, Irene T1 - Structure and Function of TPC1 Vacuole SV Channel Gains Shape JF - Molecular Plant N2 - Plants and animals in endosomes operate TPC1/SV-type cation channels. All plants harbor at least one TPC1 gene. Although the encoded SV channel was firstly discovered in the plant vacuole membrane two decades ago, its biological function has remained enigmatic. Recently, the structure of a plant TPC1/SV channel protein was determined. Insights into the 3D topology has now guided site-directed mutation approaches, enabling structure–function analyses of TPC1/SV channels to shed new light on earlier findings. Fou2 plants carrying a hyperactive mutant form of TPC1 develop wounding stress phenotypes. Recent studies with fou2 and mutants that lack functional TPC1 have revealed atypical features in local and long-distance stress signaling, providing new access to the previously mysterious biology of this vacuolar cation channel type in planta. KW - Ca2+ sensors KW - TPC1/SV channel KW - vacuole membrane voltage KW - voltage sensor Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-228046 VL - 11 ER - TY - JOUR A1 - Dindas, Julian A1 - Scherzer, Sönke A1 - Roelfsema, M. Rob G. A1 - Meyer, Katharina von A1 - Müller, Heike M. A1 - Al-Rasheid, K. A. S. A1 - Palme, Klaus A1 - Dietrich, Petra A1 - Becker, Dirk A1 - Bennett, Malcolm J. A1 - Hedrich, Rainer T1 - AUX1-mediated root hair auxin influx governs SCFTIR1/AFB-type Ca2+ signaling JF - Nature Communications N2 - Auxin is a key regulator of plant growth and development, but the causal relationship between hormone transport and root responses remains unresolved. Here we describe auxin uptake, together with early steps in signaling, in Arabidopsis root hairs. Using intracellular microelectrodes we show membrane depolarization, in response to IAA in a concentration- and pH-dependent manner. This depolarization is strongly impaired in aux1 mutants, indicating that AUX1 is the major transporter for auxin uptake in root hairs. Local intracellular auxin application triggers Ca2+ signals that propagate as long-distance waves between root cells and modulate their auxin responses. AUX1-mediated IAA transport, as well as IAA- triggered calcium signals, are blocked by treatment with the SCFTIR1/AFB - inhibitor auxinole. Further, they are strongly reduced in the tir1afb2afb3 and the cngc14 mutant. Our study reveals that the AUX1 transporter, the SCFTIR1/AFB receptor and the CNGC14 Ca2+ channel, mediate fast auxin signaling in roots. KW - auxin KW - permeation and transport Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-225368 VL - 9 ER - TY - JOUR A1 - Lu, Jinping A1 - Dreyer, Ingo A1 - Dickinson, Miles Sasha A1 - Panzer, Sabine A1 - Jaślan, Dawid A1 - Navarro-Retamal, Carlos A1 - Geiger, Dietmar A1 - Terpitz, Ulrich A1 - Becker, Dirk A1 - Stroud, Robert M. A1 - Marten, Irene A1 - Hedrich, Rainer T1 - Vicia faba SV channel VfTPC1 is a hyperexcitable variant of plant vacuole two pore channels JF - eLife N2 - To fire action-potential-like electrical signals, the vacuole membrane requires the two-pore channel TPC1, formerly called SV channel. The TPC1/SV channel functions as a depolarization-stimulated, non-selective cation channel that is inhibited by luminal Ca\(^{2+}\). In our search for species-dependent functional TPC1 channel variants with different luminal Ca\(^{2+}\) sensitivity, we found in total three acidic residues present in Ca\(^{2+}\) sensor sites 2 and 3 of the Ca\(^{2+}\)-sensitive AtTPC1 channel from Arabidopsis thaliana that were neutral in its Vicia faba ortholog and also in those of many other Fabaceae. When expressed in the Arabidopsis AtTPC1-loss-of-function background, wild-type VfTPC1 was hypersensitive to vacuole depolarization and only weakly sensitive to blocking luminal Ca\(^{2+}\). When AtTPC1 was mutated for these VfTPC1-homologous polymorphic residues, two neutral substitutions in Ca\(^{2+}\) sensor site 3 alone were already sufficient for the Arabidopsis At-VfTPC1 channel mutant to gain VfTPC1-like voltage and luminal Ca\(^{2+}\) sensitivity that together rendered vacuoles hyperexcitable. Thus, natural TPC1 channel variants exist in plant families which may fine-tune vacuole excitability and adapt it to environmental settings of the particular ecological niche. KW - A. thaliana KW - Brassicaceae KW - Fabaceae KW - pore KW - potassium channel KW - voltage gating KW - vacuolar calcium sensor Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-350264 VL - 12 ER - TY - JOUR A1 - Ghirardo, Andrea A1 - Nosenko, Tetyana A1 - Kreuzwieser, Jürgen A1 - Winkler, J. Barbro A1 - Kruse, Jörg A1 - Albert, Andreas A1 - Merl-Pham, Juliane A1 - Lux, Thomas A1 - Ache, Peter A1 - Zimmer, Ina A1 - Alfarraj, Saleh A1 - Mayer, Klaus F. X. A1 - Hedrich, Rainer A1 - Rennenberg, Heinz A1 - Schnitzler, Jörg-Peter T1 - Protein expression plasticity contributes to heat and drought tolerance of date palm JF - Oecologia N2 - Climate change is increasing the frequency and intensity of warming and drought periods around the globe, currently representing a threat to many plant species. Understanding the resistance and resilience of plants to climate change is, therefore, urgently needed. As date palm (Phoenix dactylifera) evolved adaptation mechanisms to a xeric environment and can tolerate large diurnal and seasonal temperature fluctuations, we studied the protein expression changes in leaves, volatile organic compound emissions, and photosynthesis in response to variable growth temperatures and soil water deprivation. Plants were grown under controlled environmental conditions of simulated Saudi Arabian summer and winter climates challenged with drought stress. We show that date palm is able to counteract the harsh conditions of the Arabian Peninsula by adjusting the abundances of proteins related to the photosynthetic machinery, abiotic stress and secondary metabolism. Under summer climate and water deprivation, these adjustments included efficient protein expression response mediated by heat shock proteins and the antioxidant system to counteract reactive oxygen species formation. Proteins related to secondary metabolism were downregulated, except for the P. dactylifera isoprene synthase (PdIspS), which was strongly upregulated in response to summer climate and drought. This study reports, for the first time, the identification and functional characterization of the gene encoding for PdIspS, allowing future analysis of isoprene functions in date palm under extreme environments. Overall, the current study shows that reprogramming of the leaf protein profiles confers the date palm heat- and drought tolerance. We conclude that the protein plasticity of date palm is an important mechanism of molecular adaptation to environmental fluctuations. KW - abiotic stress KW - isoprene KW - proteomics KW - photosynthesis KW - Phoenix dactylifera Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-308075 SN - 0029-8549 SN - 1432-1939 VL - 197 IS - 4 ER - TY - JOUR A1 - Rasouli, Fatemeh A1 - Kiani-Pouya, Ali A1 - Shabala, Lana A1 - Li, Leiting A1 - Tahir, Ayesha A1 - Yu, Min A1 - Hedrich, Rainer A1 - Chen, Zhonghua A1 - Wilson, Richard A1 - Zhang, Heng A1 - Shabala, Sergey T1 - Salinity effects on guard cell proteome in Chenopodium quinoa JF - International Journal of Molecular Sciences N2 - Epidermal fragments enriched in guard cells (GCs) were isolated from the halophyte quinoa (Chenopodium quinoa Wild.) species, and the response at the proteome level was studied after salinity treatment of 300 mM NaCl for 3 weeks. In total, 2147 proteins were identified, of which 36% were differentially expressed in response to salinity stress in GCs. Up and downregulated proteins included signaling molecules, enzyme modulators, transcription factors and oxidoreductases. The most abundant proteins induced by salt treatment were desiccation-responsive protein 29B (50-fold), osmotin-like protein OSML13 (13-fold), polycystin-1, lipoxygenase, alpha-toxin, and triacylglycerol lipase (PLAT) domain-containing protein 3-like (eight-fold), and dehydrin early responsive to dehydration (ERD14) (eight-fold). Ten proteins related to the gene ontology term “response to ABA” were upregulated in quinoa GC; this included aspartic protease, phospholipase D and plastid-lipid-associated protein. Additionally, seven proteins in the sucrose–starch pathway were upregulated in the GC in response to salinity stress, and accumulation of tryptophan synthase and L-methionine synthase (enzymes involved in the amino acid biosynthesis) was observed. Exogenous application of sucrose and tryptophan, L-methionine resulted in reduction in stomatal aperture and conductance, which could be advantageous for plants under salt stress. Eight aspartic proteinase proteins were highly upregulated in GCs of quinoa, and exogenous application of pepstatin A (an inhibitor of aspartic proteinase) was accompanied by higher oxidative stress and extremely low stomatal aperture and conductance, suggesting a possible role of aspartic proteinase in mitigating oxidative stress induced by saline conditions. KW - quinoa KW - guard cell KW - stomata KW - salt stress KW - proteomics analysis Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-285625 SN - 1422-0067 VL - 22 IS - 1 ER -