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Publikationen - Molekulare Signalverarbeitung

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Publikation

Wasternack, C. Action of jasmonates in plant stress responses and development — Applied aspects Biotechnol Adv 32 , 31-39, (2014) DOI: 10.1016/j.biotechadv.2013.09.009

Jasmonates (JAs) are lipid-derived compounds acting as key signaling compounds in plant stress responses and development. The JA co-receptor complex and several enzymes of JA biosynthesis have been crystallized, and various JA signal transduction pathways including cross-talk to most of the plant hormones have been intensively studied. Defense to herbivores and necrotrophic pathogens are mediated by JA. Other environmental cues mediated by JA are light, seasonal and circadian rhythms, cold stress, desiccation stress, salt stress and UV stress. During development growth inhibition of roots, shoots and leaves occur by JA, whereas seed germination and flower development are partially affected by its precursor 12-oxo-phytodienoic acid (OPDA). Based on these numerous JA mediated signal transduction pathways active in plant stress responses and development, there is an increasing interest in horticultural and biotechnological applications. Intercropping, the mixed growth of two or more crops, mycorrhization of plants, establishment of induced resistance, priming of plants for enhanced insect resistance as well as pre- and post-harvest application of JA are few examples. Additional sources for horticultural improvement, where JAs might be involved, are defense against nematodes, biocontrol by plant growth promoting rhizobacteria, altered composition of rhizosphere bacterial community, sustained balance between growth and defense, and improved plant immunity in intercropping systems. Finally, biotechnological application for JA-induced production of pharmaceuticals and application of JAs as anti-cancer agents were intensively studied.
Publikation

Bürstenbinder, K.; Savchenko, T.; Müller, J.; Adamson, A.W.; Stamm, G.; Kwong, R.; Zipp, B.J.; Dhurvas Chandrasekaran, D. & Abel, S. Arabidopsis calmodulin-binding protein IQ67-domain 1 localizes to microtubules and interacts with kinesin light chain-related protein-1 J Biol Chem 288, 1871-1882, (2013) DOI: 10.1074/jbc.M112.396200

Calcium (Ca2+) is a key second messenger in eukaryotes and regulates diverse cellular processes, most notably via calmodulin (CaM). In Arabidopsis thaliana, IQD1 (IQ67 domain 1) is the founding member of the IQD family of putative CaM targets. The 33 predicted IQD proteins share a conserved domain of 67 amino acids that is characterized by a unique arrangement of multiple CaM recruitment motifs, including so-called IQ motifs. Whereas IQD1 has been implicated in the regulation of defense metabolism, the biochemical functions of IQD proteins remain to be elucidated. In this study we show that IQD1 binds to multiple Arabidopsis CaM and CaM-like (CML) proteins in vitro and in yeast two-hybrid interaction assays. CaM overlay assays revealed moderate affinity of IQD1 to CaM2 (Kd ∼ 0.6 μm). Deletion mapping of IQD1 demonstrated the importance of the IQ67 domain for CaM2 binding in vitro, which is corroborated by interaction of the shortest IQD member, IQD20, with Arabidopsis CaM/CMLs in yeast. A genetic screen of a cDNA library identified Arabidopsis kinesin light chain-related protein-1 (KLCR1) as an IQD1 interactor. The subcellular localization of GFP-tagged IQD1 proteins to microtubules and the cell nucleus in transiently and stably transformed plant tissues (tobacco leaves and Arabidopsis seedlings) suggests direct interaction of IQD1 and KLCR1 in planta that is supported by GFP∼IQD1-dependent recruitment of RFP∼KLCR1 and RFP∼CaM2 to microtubules. Collectively, the prospect arises that IQD1 and related proteins provide Ca2+/CaM-regulated scaffolds for facilitating cellular transport of specific cargo along microtubular tracks via kinesin motor proteins.
Publikation

Ziegler, J.; Brandt, W.; Geißler, R.; Facchini, P. J. Removal of Substrate Inhibition and Increase in Maximal Velocity in the Short Chain Dehydrogenase/Reductase Salutaridine Reductase Involved in Morphine Biosynthesis J Biol Chem 284, 26758-26767, (2009) DOI: 10.1074/jbc.M109.030957

Salutaridine reductase (SalR, EC 1.1.1.248) catalyzes the stereospecific reduction of salutaridine to 7(S)-salutaridinol in the biosynthesis of morphine. It belongs to a new, plant-specific class of short-chain dehydrogenases, which are characterized by their monomeric nature and increased length compared with related enzymes. Homology modeling and substrate docking suggested that additional amino acids form a novel -helical element, which is involved in substrate binding. Site-directed mutagenesis and subsequent studies on enzyme kinetics revealed the importance of three residues in this element for substrate binding. Further replacement of eight additional residues led to the characterization of the entire substrate binding pocket. In addition, a specific role in salutaridine binding by either hydrogen bond formation or hydrophobic interactions was assigned to each amino acid. Substrate docking alsorevealed an alternative mode for salutaridine binding, which could explain the strong substrate inhibition of SalR. An alternate arrangement of salutaridine in the enzyme was corroborated by the effect of various amino acid substitutions on substrate inhibition. In most cases, the complete removal of substrate inhibition was accompanied by a substantial loss in enzyme activity. However, some mutations greatly reduced substrate inhibition while maintaining or even increasing the maximal velocity. Based on these results, a double mutant of SalRwas created that exhibited the complete absence of substrate inhibition and higher activity compared with wild-type SalR.
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