@Article{IPB-2277, author = {Naumann, C. and Müller, J. and Sakhonwasee, S. and Wieghaus, A. and Hause, G. and Heisters, M. and Bürstenbinder, K. and Abel, S.}, title = {{The Local Phosphate Deficiency Response Activates Endoplasmic Reticulum Stress-Dependent Autophagy}}, year = {2019}, pages = {460-476}, journal = {Plant Physiol}, doi = {10.1104/pp.18.01379}, url = {https://dx.doi.org/10.1104/pp.18.01379}, volume = {179}, abstract = {Inorganic phosphate (Pi) is often a limiting plant nutrient. In members of the Brassicaceae family, such as Arabidopsis (Arabidopsis thaliana), Pi deprivation reshapes root system architecture to favor topsoil foraging. It does so by inhibiting primary root extension and stimulating lateral root formation. Root growth inhibition from phosphate (Pi) deficiency is triggered by iron-stimulated, apoplastic reactive oxygen species generation and cell wall modifications, which impair cell-to-cell communication and meristem maintenance. These processes require LOW PHOSPHATE RESPONSE1 (LPR1), a cell wall-targeted ferroxidase, and PHOSPHATE DEFICIENCY RESPONSE2 (PDR2), the single endoplasmic reticulum (ER)-resident P5-type ATPase (AtP5A), which is thought to control LPR1 secretion or activity. Autophagy is a conserved process involving the vacuolar degradation of cellular components. While the function of autophagy is well established under nutrient starvation (C, N, or S), it remains to be explored under Pi deprivation. Because AtP5A/PDR2 likely functions in the ER stress response, we analyzed the effect of Pi limitation on autophagy. Our comparative study of mutants defective in the local Pi deficiency response, ER stress response, and autophagy demonstrated that ER stress-dependent autophagy is rapidly activated as part of the developmental root response to Pi limitation and requires the genetic PDR2-LPR1 module. We conclude that Pi-dependent activation of autophagy in the root apex is a consequence of local Pi sensing and the associated ER stress response, rather than a means for systemic recycling of the macronutrient.} } @Article{IPB-2342, author = {Chutia, R. and Abel, S. and Ziegler, J.}, title = {{Iron and Phosphate Deficiency Regulators Concertedly Control Coumarin Profiles in Arabidopsis thaliana Roots During Iron, Phosphate, and Combined Deficiencies}}, year = {2019}, pages = {113}, journal = {Front Plant Sci}, doi = {10.3389/fpls.2019.00113}, url = {https://dx.doi.org/10.3389/fpls.2019.00113}, volume = {10}, abstract = {Plants face varying nutrient conditions, to which they have to adapt to. Adaptive responses are nutrient-specific and strategies to ensure supply and homeostasis for one nutrient might be opposite to another one, as shown for phosphate (Pi) and iron (Fe) deficiency responses, where many genes are regulated in an opposing manner. This was also observed on the metabolite levels. Whereas root and exudate levels of catechol-type coumarins, phenylpropanoid-derived 2-benzopyranones, which facilitate Fe acquisition, are elevated after Fe deficiency, they are decreased after Pi deficiency. Exposing plants to combined Pi and Fe deficiency showed that the generation of coumarin profiles in Arabidopsis thaliana roots by Pi deficiency considerably depends on the availability of Fe. Similarly, the effect of Fe deficiency on coumarin profiles is different at low compared to high Pi availability. These findings suggest a fine-tuning of coumarin profiles, which depends on Fe and Pi availability. T-DNA insertion lines exhibiting aberrant expression of genes involved in the regulation of Pi starvation responses (PHO1, PHR1, bHLH32, PHL1, SPX1) and Fe starvation responses (BRUTUS, PYE, bHLH104, FIT) were used to analyze the regulation of the generation of coumarin profiles in Arabidopsis thaliana roots by Pi, Fe, and combined Pi and Fe deficiency. The analysis revealed a role of several Fe-deficiency response regulators in the regulation of Fe and of Pi deficiency-induced coumarin profiles as well as for Pi deficiency response regulators in the regulation of Pi and of Fe deficiency-induced coumarin profiles. Additionally, the regulation of Fe deficiency-induced coumarin profiles by Fe deficiency response regulators is influenced by Pi availability. Conversely, regulation of Pi deficiency-induced coumarin profiles by Pi deficiency response regulators is modified by Fe availability.} } @Article{IPB-2271, author = {Mitra, D. and Klemm, S. and Kumari, P. and Quegwer, J. and Möller, B. and Poeschl, Y. and Pflug, P. and Stamm, G. and Abel, S. and Bürstenbinder, K.}, title = {{Microtubule-associated protein IQ67 DOMAIN5 regulates morphogenesis of leaf pavement cells in Arabidopsis thaliana}}, year = {2019}, pages = {529-543}, journal = {J Exp Bot}, doi = {10.1093/jxb/ery395}, url = {https://dx.doi.org/10.1093/jxb/ery395}, volume = {70}, abstract = {Plant microtubules form a highly dynamic intracellular network with important roles for regulating cell division, cell proliferation and cell morphology. Its organization and dynamics are coordinated by various microtubule-associated proteins (MAPs) that integrate environmental and developmental stimuli to fine-tune and adjust cytoskeletal arrays. IQ67 DOMAIN (IQD) proteins recently emerged as a class of plant-specific MAPs with largely unknown functions. Here, using a reverse genetics approach, we characterize Arabidopsis IQD5 in terms of its expression domains, subcellular localization and biological functions. We show that IQD5 is expressed mostly in vegetative tissues, where it localizes to cortical microtubule arrays. Our phenotypic analysis of iqd5 loss-of-function lines reveals functions of IQD5 in pavement cell (PC) shape morphogenesis. Histochemical analysis of cell wall composition further suggests reduced rates of cellulose deposition in anticlinal cell walls, which correlate with reduced anisotropic expansion. Lastly, we demonstrate IQD5-dependent recruitment of calmodulin calcium sensors to cortical microtubule arrays and provide first evidence for important roles of calcium in regulation of PC morphogenesis. Our work thus identifies IQD5 as a novel player in PC shape regulation, and, for the first time, links calcium signaling to developmental processes that regulate anisotropic growth in PCs.} } @Article{IPB-2527, author = {Wasternack, C. and Hause, B. and Abel, S.}, title = {{Benno Parthier (1932–2019)}}, year = {2019}, pages = {519-520}, journal = {Plant Mol Biol}, doi = {10.1007/s11103-019-00927-6}, url = {https://dx.doi.org/10.1007/s11103-019-00927-6}, volume = {101}, } @INBOOK{IPB-2452, author = {Ziegler, J. and Hussain, H. and Neubert, R. H. H. and Abel, S.}, title = {{Amino Acid Analysis}}, year = {2019}, pages = {365-379}, chapter = {{Sensitive and Selective Amino Acid Profiling of Minute Tissue Amounts by HPLC/Electrospray Negative Tandem Mass Spectrometry Using 9-Fluorenylmethoxycarbonyl (Fmoc-Cl) Derivatization}}, journal = {Methods Mol Biol}, editor = {Alterman, M. A., ed.}, doi = {10.1007/978-1-4939-9639-1_27}, url = {https://dx.doi.org/10.1007/978-1-4939-9639-1_27}, volume = {2030}, abstract = {A method for selective and sensitive quantification of amino acids is described. The combination of established derivatization procedures of secondary and primary amino groups with 9-fluorenylmethoxycarbonyl chloride (Fmoc-Cl) and subsequent detection of derivatized amino acids by LC-ESI-MS/MS using multiple reaction monitoring provides high selectivity. The attachment of an apolar moiety enables purification of derivatized amino acids from matrix by a single solid-phase extraction step, which increases sensitivity by reduced ion suppression during LC-ESI-MS/MS detection. Additionally, chromatography of all amino acids can be performed on reversed-phase HPLC columns using eluents without additives, which are known to cause significant decreases in signal to noise ratios. The method has been routinely applied for amino acid profiling of low amounts of liquids and tissues of various origins with a sample throughput of about 50–100 samples a day. In addition to a detailed description of the method, some representative examples are presented.} } @Article{IPB-1134, author = {Abel, S. and Ticconi, C.A. and Delatorre, C.A.}, title = {{Phosphate sensing in higher plants}}, year = {2002}, pages = {1 - 8}, journal = {Plant Physiology}, volume = {115}, } @Article{IPB-1294, author = {Laskowski, M.J. and Dreher, K.A. and Gehring, M. and Abel, S. and Gensler, A. and Sussex, I.M.}, title = {{FQR1, a novel primary auxin-response gene, encodes an FMN-binding quinone reductase.}}, year = {2002}, pages = {578-686}, journal = {Plant Physiology}, url = {http://www.plantphysiol.org/content/128/2/578.abstract?sid=3f1f8a7a-ed15-40f3-9d7f-723ae31566f1}, volume = {128}, abstract = { FQR1 is a novel primary auxin-response gene that codes for a flavin mononucleotide-binding flavodoxin-like quinone reductase. Accumulation of FQR1 mRNA begins within 10 min of indole-3-acetic acid application and reaches a maximum of approximately 10-fold induction 30 min after treatment. This increase in FQR1 mRNA abundance is not diminished by the protein synthesis inhibitor cycloheximide, demonstrating thatFQR1 is a primary auxin-response gene. Sequence analysis reveals that FQR1 belongs to a family of flavin mononucleotide-binding quinone reductases. Partially purified His-tagged FQR1 isolated fromEscherichia coli catalyzes the transfer of electrons from NADH and NADPH to several substrates and exhibits in vitro quinone reductase activity. Overexpression of FQR1 in plants leads to increased levels of FQR1 protein and quinone reductase activity, indicating that FQR1 functions as a quinone reductase in vivo. In mammalian systems, glutathione S-transferases and quinone reductases are classified as phase II detoxification enzymes. We hypothesize that the auxin-inducible glutathioneS-transferases and quinone reductases found in plants also act as detoxification enzymes, possibly to protect against auxin-induced oxidative stress.} } @Article{IPB-355, author = {Vigliocco, A. and Bonamico, M.B. and Alemano, S. and Miersch, O. and Abdala, G.}, title = {{Activation of jasmonic acid production in Zea mays L. infected by the maize rough dwarf virus-Río Cuarto. Reversion of symptoms by salicylic acid}}, year = {2002}, pages = {369-374}, journal = {Biocell}, volume = {26(3)}, } @Article{IPB-1145, author = {Wang, Q. and Grubb, C.D. and Abel, S.}, title = {{Direct analysis of single leaf disks for chemopreventive glucosinolates}}, year = {2002}, pages = {152 - 157}, journal = {Phytochem Anal}, doi = {10.1002/pca.636}, url = {http://onlinelibrary.wiley.com/doi/10.1002/pca.636/abstract}, volume = {13}, abstract = {Natural isothiocyanates, produced during plant tissue damage from methionine-derived glucosinolates, are potent inducers of mammalian phase 2 detoxification enzymes such as quinone reductase (QR). A greatly simplified bioassay for glucosinolates based on induction and colorimetric detection of QR activity in murine hepatoma cells is described. It is demonstrated that excised leaf disks of Arabidopsis thaliana (ecotype Columbia) can directly and reproducibly substitute for cell-free leaf extracts as inducers of murine QR, which reduces sample preparation to a minimum and maximizes throughput. A comparison of 1 and 3 mm diameter leaf disks indicated that QR inducer potency was proportional to disk circumference (extent of tissue damage) rather than to area. When compared to the QR inducer potency of the corresponding amount of extract, 1 mm leaf disks were equally effective, whereas 3 mm disks were 70% as potent. The QR inducer potency of leaf disks correlated positively with the content of methionine-derived glucosinolates, as shown by the analysis of wild-type plants and mutant lines with lower or higher glucosinolate content. Thus, the microtitre plate-based assay of single leaf disks provides a robust and inexpensive visual method for rapidly screening large numbers of plants in mapping populations or mutant collections and may be applicable to other glucosinolate-producing species.} } @Article{IPB-1146, author = {Grubb, C.D. and Gross, H.B. and Chen, D.L. and Abel, S.}, title = {{Identification of Arabidopsis mutants with altered glucosinolate profiles based on isothiocyanate bioactivity}}, year = {2002}, pages = {143 - 152}, journal = {Plant Sci}, doi = {10.1016/S0168-9452(01)00550-7}, url = {http://www.sciencedirect.com/science/article/pii/S0168945201005507}, volume = {162}, abstract = {Glucosinolates are a diverse class of nitrogen- and sulfur-containing secondary metabolites. They are rapidly hydrolyzed on tissue disruption to a number of biologically active compounds that are increasingly attracting interest as anticarcinogenic phytochemicals and crop protectants. Several glucosinolate-derived isothiocyanates are potent chemopreventive agents that favorably modulate carcinogen metabolism in mammals. Methylsulfinylalkyl isothiocyanates, in particular the 4-methylsulfinylbutyl derivative, are selective and potent inducers of mammalian detoxification enzymes such as quinone reductase (QR). Cruciferous plants including Arabidopsis thaliana (L.) Heyhn, synthesize methylsulfinylalkyl glucosinolates, which are derived from methionine. Using a colorimetric assay for QR activity in murine hepatoma cells and high performance liquid chromatography (HPLC) analysis of desulfoglucosinolates, we have demonstrated a strong positive correlation between leaf QR inducer potency and leaf content of methionine-derived glucosinolates in various A. thaliana ecotypes and available glucosinolate mutants. In a molecular genetic approach to glucosinolate biosynthesis, we screened 3000 chemically mutagenized M2 plants of the Columbia ecotype for altered leaf QR inducer potency. Subsequent HPLC analysis of progeny of putative mutants identified six lines with significant and heritable changes in leaf glucosinolate content and composition.} } @Article{IPB-1293, author = {Schwechheimer, C. and Calderón Villalobos, L.I.}, title = {{Cullin-containing E3 ubiquitin ligases in plant development}}, year = {2002}, pages = {677-686}, journal = {Curr. Opin. Plant Biol.}, url = {http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%236252%232004%23999929993%23523857%23FLA%23&_cdi=6252&_pubType=J&_auth=y&_acct=C000065317&_version=1&_urlVersion=0&_userid=4832532&md5=c784aeed2f5d5cdf916aeca40dee0117}, volume = {7(6)}, abstract = { In eukaryotes, the ubiquitinproteasome system participates in the control of signal transduction events by selectively eliminating regulatory proteins. E3 ubiquitin ligases specifically bind degradation substrates and mediate their poly-ubiquitylation, a prerequisite for their degradation by the 26S proteasome. On the basis of the analysis of the Arabidopsis genome sequence, it is predicted that there are more than 1000 E3 ubiquitin ligases in plants. Several types of E3 ubiquitin ligases have already been characterized in eukaryotes. Recently, some of these E3 enzymes have been implicated in specific plant signaling pathways.} } @Article{IPB-1300, author = {Abel, S. and Theologis, A.}, title = {{A polymorphic bipartite motif signals nuclear targeting of early auxin- inducible proteins related to PS-IAA4 from pea (Pisum sativum)}}, year = {1995}, pages = {87-96}, journal = {Plant Journal}, url = {http://onlinelibrary.wiley.com/doi/10.1046/j.1365-313X.1995.08010087.x/abstract}, volume = {8}, abstract = { The plant hormone, indoleacetic acid (IAA), transcriptionally activates two early genes in pea, PS-IAA4/5 and PS-IAA6, that encode short-lived nuclear proteins. The identification of the nuclear localization signals (NLS) in PS-IAA4 and PS-IAA6 using progressive deletion analysis and site-directed mutagenesis is reported. A C-terminal SV40-type NLS is sufficient to direct the β-glucuronidase reporter to the nucleus of transiently transformed tobacco protoplasts, but is dispensible for nuclear localization of both proteins. The dominant and essential NLS in PS-IAA4 and PS-IAA6 overlap with a bipartite basic motif which is polymorphic and conserved in related proteins from other plant species, having the consensus sequence (KKNEK)KR-X(2471)-(RSXRK)/(RK/RK). Both basic elements of this motif in PS-IAA4, (KR-X41-RSYRK), function interdependently as a bipartite NLS. However, in PS-IAA6 (KKNEKKR-X36-RKK) the upstream element of the corresponding motif contains additional basic residues which allow its autonomous function as an SV40-type monopartite NLS. The spacer-length polymorphism, X(2470), in respective bipartite NLS peptides of several PS-IAA4-like proteins from Arabidopsis thaliana does not affect nuclear targeting function. The structural and functional variation of the bipartite basic motif in PS-IAA4-like proteins supports the proposed integrated consensus of NLS.} } @Article{IPB-1301, author = {Abel, S. and Nguyen, M.D. and Theologis, A.}, title = {{The PS-IAA4/5-like family of early auxin-inducible mRNAs in Arabidopsis thaliana}}, year = {1995}, pages = {19093-19099}, journal = {Journal of Biological Chemistry}, url = {http://www.jbc.org/content/270/32/19093.abstract?sid=c17d6e17-db5e-4424-8236-1c3dccb9ded2}, volume = {270}, abstract = { 1-Aminocyclopropane-1-carboxylic acid (ACC) synthase is the key regulatory enzyme in the biosynthetic pathway of the plant hormone ethylene. The enzyme is encoded by a divergent multigene family in Arabidopsis thaliana, comprising at least five genes, ACS1-5 (Liang, X., Abel, S., Keller, J. A., Shen, N. F., and Theologis, A.(1992) Proc. Natl. Acad. Sci. U. S. A. 89, 11046-11050). In etiolated seedlings, ACS4 is specifically induced by indoleacetic acid (IAA). The response to IAA is rapid (within 25 min) and insensitive to protein synthesis inhibition, suggesting that the ACS4 gene expression is a primary response to IAA. The ACS4 mRNA accumulation displays a biphasic dose-response curve which is optimal at 10 μM of IAA. However, IAA concentrations as low as 100 nM are sufficient to enhance the basal level of ACS4 mRNA. The expression of ACS4 is defective in the Arabidopsis auxin-resistant mutant lines axr1-12, axr2-1, and aux1-7. ACS4 mRNA levels are severely reduced in axr1-12 and axr2-1 but are only 1.5-fold lower in aux1-7. IAA inducibility is abolished in axr2-1. The ACS4 gene was isolated and structurally characterized. The promoter contains four sequence motifs reminiscent of functionally defined auxin-responsive cis-elements in the early auxin-inducible genes PS-IAA4/5 from pea and GH3 from soybean. Conceptual translation of the coding region predicts a protein with a molecular mass of 53,795 Da and a theoretical isoelectric point of 8.2. The ACS4 polypeptide contains the 11 invariant amino acid residues conserved between aminotransferases and ACC synthases from various plant species. An ACS4 cDNA was generated by reverse transcriptase-polymerase chain reaction, and the authenticity was confirmed by expression of ACC synthase activity in Escherichia coli.} }