DynaMo Mini Symposium: Hell & Glawischnig

DynaMo is happy to invite to a Mini Symposium with two distinguised guests from Germany Dr. Rüdiger Hell and Dr. Erich Glawischnig.

Programme

10:00
Professor Dr. Rüdiger Hell, Centre for Organismal Studies, Universität Heidelberg
Cysteine synthesis in plants – lessons from a simple primary pathway

11:00
PD Dr. Erich Glawischnig, Lehrstuhl für Genetik, Technische Universität München
Camalexin induction within the tryptophan metabolic network

Abstracts

Rüdiger Hell: Cysteine synthesis in plants – lessons from a simple primary pathway

Cysteine is the primary product of assimilatory sulfate reduction with a strong impact on plant growth and stress resistance. The numerous functions of sulfur from cysteine include protein structure, electron transport and redox processes in regulation, catalysis, detoxification and defense. The biosynthesis of cysteine has a central position not only in sulfate uptake and reductive assimilation, but also in channeling of reduced sulfur into downstream metabolism according to nutritional status, developmental stage and stress conditions. The control of the network of primary metabolism is based on an unexpected subcellular compartmentation of cysteine synthesis enzymes and the unique properties of the cysteine synthase multimeric complex. Together these features give rise to a regulatory system that links sensing of sulfide as marker of the cell’s sulfate status with uptake of inorganic sulfate.

Erich Glawischnig: Camalexin induction within the tryptophan metabolic network

In plants, tryptophan plays an essential role as protein component and precursor of the phytohormone auxin. Multiple copies of tryptophan synthase (TS) subunits with diversified functions have evolved. We have identified the functional TS alpha-subunit and maize and demonstrated that alternative beta-subunits are common to plants.

Moreover, numerous tryptophan metabolites are involved in defence. Camalexin is the characteristic phytoalexin of Arabidopsis and important for defense against a number of fungal pathogens. Its biosynthetic pathway from tryptophan and glutathione involves multiple cytochrome P450 enzymes. Here, a key intermediate is indole-3-acetonitrile (IAN), which emerges as precursor of a number of defense-related metabolites, such as derivatives of indole-3-carboxylic acid. Specific for camalexin biosynthesis, an exceptional bifunctional P450, CYP71B15 (PAD3), catalyzes cyanide release from Cys(IAN) under formation of a thiazoline ring as well as the subsequent decarboxylation yielding camalexin. The biosynthetic genes are highly coregulated on transcriptional level and CYP71B15p:CYP71B15-GFP expression reveals cellular specificity of camalexin synthesis in response to pathogen infection. Based on metabolomic analysis of camalexin biosynthetic mutants, incorporation experiments, and in vitro characterization of enzymatic activities, a model of the biosynthetic network of induced indolic defense compounds in Arabidopsis is presented.