@misc{JohnsonRammKappeletal.2015, author = {Johnson, Kim L. and Ramm, Sascha and Kappel, Christian and Ward, Sally and Leyser, Ottoline and Sakamoto, Tomoaki and Kurata, Tetsuya and Bevan, Michael W. and Lenhard, Michael}, title = {The tinkerbell (tink) mutation identifies the dual-specificity MAPK phosphatase INDOLE- 3-BUTYRIC ACID-RESPONSE5 (IBR5) as a novel regulator of organ size in Arabidopsis}, series = {PLoS ONE}, journal = {PLoS ONE}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-410245}, pages = {17}, year = {2015}, abstract = {Mitogen-activated dual-specificity MAPK phosphatases are important negative regulators in the MAPK signalling pathways responsible for many essential processes in plants. In a screen for mutants with reduced organ size we have identified a mutation in the active site of the dual-specificity MAPK phosphatase INDOLE-3-BUTYRIC ACID-RESPONSE5 (IBR5) that we named tinkerbell (tink) due to its small size. Analysis of the tink mutant indicates that IBR5 acts as a novel regulator of organ size that changes the rate of growth in petals and leaves. Organ size and shape regulation by IBR5 acts independently of the KLU growth-regulatory pathway. Microarray analysis of tink/ibr5-6 mutants identified a likely role for this phosphatase in male gametophyte development. We show that IBR5 may influence the size and shape of petals through auxin and TCP growth regulatory pathways.}, language = {en} } @article{PoxsonKaradyGabrielssonetal.2017, author = {Poxson, David J. and Karady, Michal and Gabrielsson, Roger and Alkattan, Aziz Y. and Gustavsson, Anna and Doyle, Siamsa M. and Robert, Stephanie and Ljung, Karin and Grebe, Markus and Simon, Daniel T. and Berggren, Magnus}, title = {Regulating plant physiology with organic electronics}, series = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {114}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, publisher = {National Acad. of Sciences}, address = {Washington}, issn = {0027-8424}, doi = {10.1073/pnas.1617758114}, pages = {4597 -- 4602}, year = {2017}, abstract = {The organic electronic ion pump (OEIP) provides flow-free and accurate delivery of small signaling compounds at high spatio-temporal resolution. To date, the application of OEIPs has been limited to delivery of nonaromatic molecules to mammalian systems, particularly for neuroscience applications. However, many long-standing questions in plant biology remain unanswered due to a lack of technology that precisely delivers plant hormones, based on cyclic alkanes or aromatic structures, to regulate plant physiology. Here, we report the employment of OEIPs for the delivery of the plant hormone auxin to induce differential concentration gradients and modulate plant physiology. We fabricated OEIP devices based on a synthesized dendritic polyelectrolyte that enables electrophoretic transport of aromatic substances. Delivery of auxin to transgenic Arabidopsis thaliana seedlings in vivo was monitored in real time via dynamic fluorescent auxin-response reporters and induced physiological responses in roots. Our results provide a starting point for technologies enabling direct, rapid, and dynamic electronic interaction with the biochemical regulation systems of plants.}, language = {en} } @article{WangLiMaetal.2021, author = {Wang, Meng and Li, Panpan and Ma, Yao and Nie, Xiang and Grebe, Markus and Men, Shuzhen}, title = {Membrane sterol composition in Arabidopsis thaliana affects root elongation via auxin biosynthesis}, series = {International journal of molecular sciences}, volume = {22}, journal = {International journal of molecular sciences}, number = {1}, publisher = {MDPI}, address = {Basel}, issn = {1422-0067}, doi = {10.3390/ijms22010437}, pages = {20}, year = {2021}, abstract = {Plant membrane sterol composition has been reported to affect growth and gravitropism via polar auxin transport and auxin signaling. However, as to whether sterols influence auxin biosynthesis has received little attention. Here, by using the sterol biosynthesis mutant cyclopropylsterol isomerase1-1 (cpi1-1) and sterol application, we reveal that cycloeucalenol, a CPI1 substrate, and sitosterol, an end-product of sterol biosynthesis, antagonistically affect auxin biosynthesis. The short root phenotype of cpi1-1 was associated with a markedly enhanced auxin response in the root tip. Both were neither suppressed by mutations in polar auxin transport (PAT) proteins nor by treatment with a PAT inhibitor and responded to an auxin signaling inhibitor. However, expression of several auxin biosynthesis genes TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS1 (TAA1) was upregulated in cpi1-1. Functionally, TAA1 mutation reduced the auxin response in cpi1-1 and partially rescued its short root phenotype. In support of this genetic evidence, application of cycloeucalenol upregulated expression of the auxin responsive reporter DR5:GUS (beta-glucuronidase) and of several auxin biosynthesis genes, while sitosterol repressed their expression. Hence, our combined genetic, pharmacological, and sterol application studies reveal a hitherto unexplored sterol-dependent modulation of auxin biosynthesis during Arabidopsis root elongation.}, language = {en} } @phdthesis{Dolniak2005, author = {Dolniak, Blazej}, title = {Functional characterisation of NIC2, a member of the MATE family from Arabidopsis thaliana (L.) Heynh.}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-5372}, school = {Universit{\"a}t Potsdam}, year = {2005}, abstract = {The multidrug and toxic compounds extrusion (MATE) family includes hundreds of functionally uncharacterised proteins from bacteria and all eukaryotic kingdoms except the animal kingdom, that function as drug/toxin::Na+ or H+ antiporters. In Arabidopsis thaliana the MATE family comprises 56 members, one of which is NIC2 (Novel Ion Carrier 2). Using heterologous expression systems including Escherichia coli and Saccharomyces cerevisiae, and the homologous expression system of Arabidopsis thaliana, the functional characterisation of NIC2 was performed. It has been demonstrated that NIC2 confers resistance of E. coli towards the chemically diverse compounds such as tetraethylammonium chloride (TEACl), tetramethylammonium chloride (TMACl) and a toxic analogue of indole-3-acetic acid, 5-fluoro-indole-acetic acid (F-IAA). Therefore, NIC2 may be able to transport a broad range of drug and toxic compounds. In wild-type yeast the expression of NIC2 increased the tolerance towards lithium and sodium, but not towards potassium and calcium. In A. thaliana, the overexpression of NIC2 led to strong phenotypic changes. Under normal growth condtions overexpression caused an extremely bushy phenotype with no apical dominance but an enhanced number of lateral flowering shoots. The amount of rossette leaves and flowers with accompanying siliques were also much higher than in wild-type plants and the senescence occurred earlier in the transgenic plants. In contrast, RNA interference (RNAi) used to silence NIC2 expression, induced early flower stalk development and flowering compared with wild-type plants. In additon, the main flower stalks were not able to grow vertically, but instead had a strong tendency to bend towards the ground. While NIC2 RNAi seedlings produced many lateral roots outgrowing from the primary root and the root-shoot junction, NIC2 overexpression seedlings displayed longer primary roots that were characterised by a 2 to 4 h delay in the gravitropic response. In addition, these lines exhibited an enhanced resistance to exogenously applied auxins, i.e. indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) when compared with the wild-type roots. Based on these results, it is suggested that the NIC2 overexpression and NIC2 RNAi phenotypes were due to decreased or increased levels of auxin, respectively. The ProNIC2:GUS fusion gene revealed that NIC2 is expressed in the stele of the elongation zone, in the lateral root cap, in new lateral root primordia, and in pericycle cells of the root system. In the vascular tissue of rosette leaves and inflorescence stems, the expression was observed in the xylem parenchyma cells, while in siliques it was also in vascular tissue, but as well in the dehiscence and abscission zones. The organ- and tissue-specific expression sites of NIC2 correlate with the sites of auxin action in mature Arabidopsis plants. Further experiments using ProNIC2:GUS indicated that NIC2 is an auxin-inducible gene. Additionally, during the gravitropic response when an endogenous auxin gradient across the root tip forms, the GUS activity pattern of the ProNIC2:GUS fusion gene markedly changed at the upper side of the root tip, while at the lower side stayed unchanged. Finally, at the subcellular level NIC2-GFP fusion protein localised in the peroxisomes of Nicotana tabacum BY2 protoplasts. Considering the experimental results, it is proposed that the hypothetical function of NIC2 is the efflux transport which takes part in the auxin homeostasis in plant tissues probably by removing auxin conjugates from the cytoplasm into peroxisomes.}, subject = {Ackerschmalwand}, language = {en} } @article{BemervanMourikMuinoetal.2017, author = {Bemer, Marian and van Mourik, Hilda and Muino, Jose M. and Ferrandiz, Cristina and Kaufmann, Kerstin and Angenent, Gerco C.}, title = {FRUITFULL controls SAUR10 expression and regulates Arabidopsis growth and architecture}, series = {Journal of experimental botany}, volume = {68}, journal = {Journal of experimental botany}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0022-0957}, doi = {10.1093/jxb/erx184}, pages = {3391 -- 3403}, year = {2017}, abstract = {MADS-domain transcription factors are well known for their roles in plant development and regulate sets of downstream genes that have been uncovered by high-throughput analyses. A considerable number of these targets are predicted to function in hormone responses or responses to environmental stimuli, suggesting that there is a close link between developmental and environmental regulators of plant growth and development. Here, we show that the Arabidopsis MADS-domain factor FRUITFULL (FUL) executes several functions in addition to its noted role in fruit development. Among the direct targets of FUL, we identified SMALL AUXIN UPREGULATED RNA 10 (SAUR10), a growth regulator that is highly induced by a combination of auxin and brassinosteroids and in response to reduced R:FR light. Interestingly, we discovered that SAUR10 is repressed by FUL in stems and inflorescence branches. SAUR10 is specifically expressed at the abaxial side of these branches and this localized activity is influenced by hormones, light conditions and by FUL, which has an effect on branch angle. Furthermore, we identified a number of other genes involved in hormone pathways and light signalling as direct targets of FUL in the stem, demonstrating a connection between developmentally and environmentally regulated growth programs.}, language = {en} } @misc{PowellLenhard2012, author = {Powell, Anahid E. and Lenhard, Michael}, title = {Control of organ size in plants}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch Naturwissenschaftliche Reihe}, number = {898}, issn = {1866-8372}, doi = {10.25932/publishup-43802}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-438029}, pages = {10}, year = {2012}, abstract = {The size of plant organs, such as leaves and flowers, is determined by an interaction of genotype and environmental influences. Organ growth occurs through the two successive processes of cell proliferation followed by cell expansion. A number of genes influencing either or both of these processes and thus contributing to the control of final organ size have been identified in the last decade. Although the overall picture of the genetic regulation of organ size remains fragmentary, two transcription factor/microRNA-based genetic pathways are emerging in the control of cell proliferation. However, despite this progress, fundamental questions remain unanswered, such as the problem of how the size of a growing organ could be monitored to determine the appropriate time for terminating growth. While genetic analysis will undoubtedly continue to advance our knowledge about size control in plants, a deeper understanding of this and other basic questions will require including advanced live-imaging and mathematical modeling, as impressively demonstrated by some recent examples. This should ultimately allow the comparison of the mechanisms underlying size control in plants and in animals to extract common principles and lineage-specific solutions.}, language = {en} } @phdthesis{AranaCeballos2006, author = {Arana-Ceballos, Fernando Alberto}, title = {Biochemical and physiological studies of Arabidopsis thaliana Diacylglycerol Kinase 7 (AtDGK7)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-13729}, school = {Universit{\"a}t Potsdam}, year = {2006}, abstract = {A family of diacylglycerol kinases (DGK) phosphorylates the substrate diacylglycerol (DAG) to generate phosphatidic acid (PA) . Both molecules, DAG and PA, are involved in signal transduction pathways. In the model plant Arabidopsis thaliana, seven candidate genes (named AtDGK1 to AtDGK7) code for putative DGK isoforms. Here I report the molecular cloning and characterization of AtDGK7. Biochemical, molecular and physiological experiments of AtDGK7 and their corresponding enzyme are analyzed. Information from Genevestigator says that AtDGK7 gene is expressed in seedlings and adult Arabidopsis plants, especially in flowers. The AtDGK7 gene encodes the smallest functional DGK predicted in higher plants; but also, has an alternative coding sequence containing an extended AtDGK7 open reading frame, confirmed by PCR and submitted to the GenBank database (under the accession number DQ350135). The new cDNA has an extension of 439 nucleotides coding for 118 additional amino acids The former AtDGK7 enzyme has a predicted molecular mass of ~41 kDa and its activity is affected by pH and detergents. The DGK inhibitor R59022 also affects AtDGK7 activity, although at higher concentrations (i.e. IC50 ~380 µM). The AtDGK7 enzyme also shows a Michaelis-Menten type saturation curve for 1,2-DOG. Calculated Km and Vmax were 36 µM 1,2-DOG and 0.18 pmol PA min-1 mg of protein-1, respectively, under the assay conditions. Former protein AtDGK7 are able to phosphorylate different DAG analogs that are typically found in plants. The new deduced AtDGK7 protein harbors the catalytic DGKc and accessory domains DGKa, instead the truncated one as the former AtDGK7 protein (Gomez-Merino et al., 2005).}, language = {en} } @article{BatistaFigueiredoSantosGonzalezetal.2019, author = {Batista, Rita A. and Figueiredo, Duarte Dionisio and Santos-Gonzalez, Juan and K{\"o}hler, Claudia}, title = {Auxin regulates endosperm cellularization in Arabidopsis}, series = {Genes \& Development}, volume = {33}, journal = {Genes \& Development}, number = {7-8}, publisher = {Cold Spring Harbor Laboratory Press}, address = {Cold Spring Harbor, NY}, issn = {0890-9369}, doi = {10.1101/gad.316554.118}, pages = {466 -- 476}, year = {2019}, abstract = {The endosperm is an ephemeral tissue that nourishes the developing embryo, similar to the placenta in mammals. In most angiosperms, endosperm development starts as a syncytium, in which nuclear divisions are not followed by cytokinesis. The timing of endosperm cellularization largely varies between species, and the event triggering this transition remains unknown. Here we show that increased auxin biosynthesis in the endosperm prevents its cellularization, leading to seed arrest. Auxin-overproducing seeds phenocopy paternal-excess triploid seeds derived from hybridizations of diploid maternal plants with tetraploid fathers. Concurrently, auxin-related genes are strongly overexpressed in triploid seeds, correlating with increased auxin activity. Reducing auxin biosynthesis and signaling reestablishes endosperm cellularization in triploid seeds and restores their viability, highlighting a causal role of increased auxin in preventing endosperm cellularization. We propose that auxin determines the time of endosperm cellularization, and thereby uncovered a central role of auxin in establishing hybridization barriers in plants.}, language = {en} }