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Publikationen - Molekulare Signalverarbeitung

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Publikation

Schumann, N.; Navarro-Quezada, A.; Ullrich, K.; Kuhl, C.; Quint, M.; Molecular Evolution and Selection Patterns of Plant F-Box Proteins with C-Terminal Kelch Repeats Plant Physiol. 155, 835-850, (2011) DOI: 10.1104/pp.110.166579

The F-box protein superfamily represents one of the largest families in the plant kingdom. F-box proteins phylogenetically organize into numerous subfamilies characterized by their carboxyl (C)-terminal protein-protein interaction domain. Among the largest F-box protein subfamilies in plant genomes are those with C-terminal kelch repeats. In this study, we analyzed the phylogeny and evolution of F-box kelch proteins/genes (FBKs) in seven completely sequenced land plant genomes including a bryophyte, a lycophyte, monocots, and eudicots. While absent in prokaryotes, F-box kelch proteins are widespread in eukaryotes. Nonplant eukaryotes usually contain only a single FBK gene. In land plant genomes, however, FBKs expanded dramatically. Arabidopsis thaliana, for example, contains at least 103 F-box genes with well-conserved C-terminal kelch repeats. The construction of a phylogenetic tree based on the full-length amino acid sequences of the FBKs that we identified in the seven species enabled us to classify FBK genes into unstable/stable/superstable categories. In contrast to superstable genes, which are conserved across all seven species, kelch domains of unstable genes, which are defined as lineage specific, showed strong signatures of positive selection, indicating adaptational potential. We found evidence for conserved protein features such as binding affinities toward A. thaliana SKP1-like adaptor proteins and subcellular localization among closely related FBKs. Pseudogenization seems to occur only rarely, but differential transcriptional regulation of close relatives may result in subfunctionalization.
Publikation

Kopycki, J.; Schmidt, J.; Abel, S.; Grubb, C. D.; Chemoenzymatic synthesis of diverse thiohydroximates from glucosinolate-utilizing enzymes from Helix pomatia and Caldicellulosiruptor saccharolyticus Biotechnol. Lett. 33, 1039-1046, (2011) DOI: 10.1007/s10529-011-0530-y

Thiohydroximates comprise a diverse class of compounds important in both biological and industrial chemistry. Their syntheses are generally limited to simple alkyl and aryl compounds with few stereocenters and a narrow range of functional groups. We hypothesized that sequential action of two recombinant enzymes, a sulfatase from Helix pomatia and a β-O-glucosidase from Caldicellulosiruptor saccharolyticus, on glucosinolates would allow synthesis of thiohydroximates from a structurally broad array of abundant precursors. We report successful synthesis of thiohydroximates of varied chemical classes, including from homochiral compounds of demonstrated biological activity. The chemoenzymatic synthetic route reported here should allow access to many, if not all, of the thiohydroximate core structures of the ~200 known naturally occurring glucosinolates. The enrichment of this group for compounds with possible pharmacological potential is discussed.
Publikation

Delker, C.; Quint, M.; Expression level polymorphisms: heritable traits shaping natural variation Trends Plant Sci. 16, 481-488, (2011) DOI: 10.1016/j.tplants.2011.05.009

Natural accessions of many species harbor a wealth of genetic variation visible in a large array of phenotypes. Although expression level polymorphisms (ELPs) in several genes have been shown to contribute to variation in diverse traits, their general impact on adaptive variation has likely been underestimated. At present, ELPs have predominantly been correlated to quantitative trait loci (eQTLs) that occupy central hubs in signaling networks, which pleiotropically affect numerous traits. To increase the sensitivity of detecting minor effect eQTLs or those that act in a trait-specific manner, we emphasize the need for more systematic approaches. This requires, but is not limited to, refining experimental designs such as reduction of tissue complexity and combinatorial methods including a priori defined networks.
Publikation

Costa, C. T.; Strieder, M. L.; Abel, S.; Delatorre, C. A.; Phosphorus and nitrogen interaction: loss of QC identity in response to P or N limitation is antecipated in pdr23 mutant Braz. J. Plant Physiol. 23, 219-229, (2011) DOI: 10.1590/S1677-04202011000300006

Changes in root architecture are an important adaptive strategy used by plants in response to limited nutrient availability to increase the odds of acquiring them. The quiescent center (QC) plays an important role by altering the meristem activity causing differentiation and therefore, inducing a determinate growth program. The arabidopsis mutant pdr23 presents primary short root in the presence of nitrate and is inefficient in the use of nucleic acids as a source of phosphorus. In this study the effect of the pdr23 mutation on the QC maintenance under low phosphorus (P) and/or nitrogen is evaluated. QC identity is maintained in wild-type in the absence of nitrate and/or phosphate if nucleic acids can be used as an alternative source of these nutrients, but not in pdr23. The mutant is not able to use nucleic acids efficiently for substitute Pi, determinate growth is observed, similar to wild-type in the total absence of P. In the absence of N pdr23 loses the expression of QC identity marker earlier than wild-type, indicating that not only the response to P is altered, but also to N. The data suggest that the mutation affects a gene involved either in the crosstalk between these nutrients or in a pathway shared by both nutrients limitation response. Moreover loss of QC identity is also observed in wild-type in the absence of N at longer limitation. Less drastic symptoms are observed in lateral roots of both genotypes.
Publikation

Abel, S.; Phosphate sensing in root development Curr. Opin. Plant Biol. 14, 303-309, (2011) DOI: 10.1016/j.pbi.2011.04.007

Phosphate (Pi) and its anhydrides constitute major nodes in metabolism. Thus, plant performance depends directly on Pi nutrition. Inadequate Pi availability in the rhizosphere is a common challenge to plants, which activate metabolic and developmental responses to maximize Pi usage and acquisition. The sensory mechanisms that monitor environmental Pi and transmit the nutritional signal to adjust root development have increasingly come into focus. Recent transcriptomic analyses and genetic approaches have highlighted complex antagonistic interactions between external Pi and Fe bioavailability and have implicated the stem cell niche as a target of Pi sensing to regulate root meristem activity.
Publikation

Delker, C.; Pöschl, Y.; Raschke, A.; Ullrich, K.; Ettingshausen, S.; Hauptmann, V.; Grosse, I.; Quint, M.; Natural Variation of Transcriptional Auxin Response Networks in Arabidopsis thaliana Plant Cell 22, 2184-2200, (2010) DOI: 10.1105/tpc.110.073957

Natural variation has been observed for various traits in Arabidopsis thaliana. Here, we investigated natural variation in the context of physiological and transcriptional responses to the phytohormone auxin, a key regulator of plant development. A survey of the general extent of natural variation to auxin stimuli revealed significant physiological variation among 20 genetically diverse natural accessions. Moreover, we observed dramatic variation on the global transcriptome level after induction of auxin responses in seven accessions. Although we detect isolated cases of major-effect polymorphisms, sequencing of signaling genes revealed sequence conservation, making selective pressures that favor functionally different protein variants among accessions unlikely. However, coexpression analyses of a priori defined auxin signaling networks identified variations in the transcriptional equilibrium of signaling components. In agreement with this, cluster analyses of genome-wide expression profiles followed by analyses of a posteriori defined gene networks revealed accession-specific auxin responses. We hypothesize that quantitative distortions in the ratios of interacting signaling components contribute to the detected transcriptional variation, resulting in physiological variation of auxin responses among accessions.
Publikation

Abel, S.; Theologis, A.; Odyssey of Auxin Cold Spring Harb. Perspect. Biol. 2, a004572, (2010) DOI: 10.1101/cshperspect.a004572

The history of plant biology is inexorably intertwined with the conception and discovery of auxin, followed by the many decades of research to comprehend its action during growth and development. Growth responses to auxin are complex and require the coordination of auxin production, transport, and perception. In this overview of past auxin research, we limit our discourse to the mechanism of auxin action. We attempt to trace the almost epic voyage from the birth of the hormonal concept in plants to the recent crystallographic studies that resolved the TIR1-auxin receptor complex, the first structural model of a plant hormone receptor. The century-long endeavor is a beautiful illustration of the power of scientific reasoning and human intuition, but it also brings to light the fact that decisive progress is made when new technologies emerge and disciplines unite.
Publikation

Ludwig-Müller, J.; Denk, K.; Cohen, J. D.; Quint, M.; An Inhibitor of Tryptophan-Dependent Biosynthesis of Indole-3-Acetic Acid Alters Seedling Development in Arabidopsis J. Plant Growth Regul. 29, 242-248, (2010) DOI: 10.1007/s00344-009-9128-1

Although polar transport and the TIR1-dependent signaling pathway of the plant hormone auxin/indole-3-acetic acid (IAA) are well characterized, understanding of the biosynthetic pathway(s) leading to the production of IAA is still limited. Genetic dissection of IAA biosynthetic pathways has been complicated by the metabolic redundancy caused by the apparent existence of several parallel biosynthetic routes leading to IAA production. Valuable complementary tools for genetic as well as biochemical analysis of auxin biosynthesis would be molecular inhibitors capable of acting in vivo on specific or general components of the pathway(s), which unfortunately have been lacking. Several indole derivatives have been previously identified to inhibit tryptophan-dependent IAA biosynthesis in an in vitro system from maize endosperm. We examined the effect of one of them, 6-fluoroindole, on seedling development of Arabidopsis thaliana and tested its ability to inhibit IAA biosynthesis in feeding experiments in vivo. We demonstrated a correlation of severe developmental defects or growth retardation caused by 6-fluoroindole with significant downregulation of de novo synthesized IAA levels, derived from the stable isotope-labeled tryptophan pool, upon treatment. Hence, 6-fluoroindole shows important features of an inhibitor of tryptophan-dependent IAA biosynthesis both in vitro and in vivo and thus may find use as a promising molecular tool for the identification of novel components of the auxin biosynthetic pathway(s).
Bücher und Buchkapitel

Yamaguchi, I.; Cohen, J. D.; Culler, A. H.; Quint, M.; Slovin, J. P.; Nakajima, M.; Yamaguchi, S.; Sakakibara, H.; Kuroha, T.; Hirai, N.; Yokota, T.; Ohta, H.; Kobayashi, Y.; Mori, H.; Sakagami, Y.; Plant Hormones (Liu, H.-W. & Mander, L., eds.). 4, 9-125, (2010) DOI: 10.1016/B978-008045382-8.00092-7

The definition of a plant hormone has not been clearly established, so the compounds classified as plant hormones often vary depending on which definition is considered. In this chapter, auxins, gibberellins (GAs), cytokinins, abscisic acid, brassinosteroids, jasmonic acid-related compounds, and ethylene are described as established plant hormones, while polyamines and phenolic compounds are not included. On the other hand, several peptides that have been proven to play a clear physiological role(s) in plant growth and development, similar to the established plant hormones, are referred. This chapter will focus primarily on the more recent discoveries of plant hormones and their impact on our current understanding of their biological role. In some cases, however, it is critical to place recent work in a proper historical context.
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