Molecular and physiological characterization of arginine and proline catabolism in Arabidopsis
Year: 2013
Type: dissertation
Abstract: Plant productivity is frequently limited by the availability of nitrogen. Understanding the mechanisms of nitrogen acquisition, storage and recycling and their role in the metabolic and regulatory network of a plant cell is important to meet the demands of a growing human population for agricultural products. While the molecular mechanisms of nitrogen acquisition and assimilation are intensively studied, less is known about storage and recycling within the plant. Therefore, the focus of this study was on the catabolism of arginine in Arabidopsis and its function in transport, storage and recycling of nitrogen, in addition to its function as building block in protein synthesis or as precursor for polyamines. Arginine biosynthesis and degradation is distributed over three cellular compartments - cytosol, plastids and mitochondria - which generates a need for specific transport systems for arginine as well as for synthesis and degradation intermediates In Arabidopsis, two intracellular arginine transporters, the basic amino acid carriers BAC1 and BAC2, were predicted to be mitochondrial proteins. I/We demonstrated the mitochondrial localization of the BAC proteins experimentally in planta and in vivo. After import into mitochondria arginine is processed by the activities of two arginase isoenzymes (ARGAH1 and ARGAH2), ornithine-(delta-)aminotransferase (delta-OAT) and (delta-)1-pyrroline-5-carboxylate dehydrogenase (P5CDH). Analysis of interaction characteristics of the arginine catabolising enzymes revealed homo- and hetero-oligomerisation of the arginase isoforms as well as homo-oligomerisation of P5CDH, pointing towards tissue specific arginase activity or pH dependent P5CDH activity. A specific polyclonal antibody against natively purified (delta-)OAT was raised, useful for pull down assays of native protein complexes from mitochondrial extracts and further investigations of enzyme complexes involving arginine degrading enzymes. Investigating the physiological role of (delta-)OAT, it was found to contribute not significantly to very early seedling development, but in later stages of development. The retarded growth of delta-oat mutants indicates an important role of (delta-)OAT activity for recycling of nitrogen from arginine in Arabidopsis and therefore an optimal plant internal nitrogen supply, directly associated with ideally plant productivity.
Source: KOPS (University of Konstanz)
Author: Gudrun Winter
Language: English
Subfield: Plant Science
Domain: Life Sciences
SDG: Zero hunger
Open Access status: green
OpenAlex ID: W792700676