Project Details
Projekt
Interaction of sulfur and nitrogen metabolism: significance of different serine sources for cysteine biosynthesis
Subject Area
Plant Physiology
Term
from 2014 to 2017
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 260023971
Cysteine is the metabolic precursor of all thiol containing organic sulfur compounds in plants, including methionine, glutathione, and glucosinolates; it is essential for protein biosynthesis. Cysteine is synthesized from reduced sulfur and O-acetylserine, the latter sulfur acceptor being generated from serine and acetyl CoA by the enzyme serine acetyltransferase. Although all enzymatic steps involved in cysteine biosynthesis have been identified at the molecular level, the route of serine provision to cysteine biosynthesis is still largely unknown. It is currently also not understood how the demand for O-acetylserine in cysteine biosynthesis is coordinated with carbon and nitrogen metabolism. This proposal aims at elucidating the significance of chloroplastic/plastidic versus mitochondrial serine production for the biosynthesis of cysteine and to identify phytohormones and genes involved in the regulation of the interaction cysteine biosynthesis with carbon and nitrogen metabolism in A. thaliana. The central hypotheses to be tested in this research are that (i) serine generated by photorespiration in the mitochondira is the dominant precursor of cysteine synthesis in autotrophic tissues in the light; (ii) serine biosynthesis in the chloroplasts/plastids takes over in autotrophic tissues in the dark and is dominant in heterotrophic tissues; (iii) the differences in serine supply for cysteine synthesis during light and dark are subject to regulation by phytohormone (in particular cytokinin) action and gene expression. To test these hypotheses, we will employ established and novel mutants in the various pathways for serine biosynthesis. In addition, we will vary the flux through the photorespiratory serine biosynthesis pathway by modulating the oxygen partial pressure and thereby the oxygenation reaction of RubisCO. Mutants and wild type plants will be exposed to conditions of expanded cysteine demand and comparatively profiled at the levels of metabolism, phytohormone contents, and mRNA transcripts. Jointly, these experiments will reveal the path of carbon supply to cysteine biosynthesis during different physiological states and under conditions of expanded cysteine demand.
DFG Programme
Research Grants
International Connection
Japan
