The role of alanine and aspartate aminotransferases in C4 photosynthesis

• Published in: Plant biology (Stuttgart, Germany) Germany), 2018-08, Vol.21 (S1)
• Main Authors: Schlüter, Urte, Bräutigam, Andrea, Droz, Jean -Marie, Schwender, Jörg, Weber, Andreas P. M.
• Format: Article
• Language: English
• Subjects: BASIC BIOLOGICAL SCIENCES
• ISSN: 1435-8603; 1438-8677

Alanine and aspartate are essential transfer metabolites for C4 species of the NAD-malic enzyme and the phosphoenolpyruvate carboxykinase subtype. To some degree both amino acids are also part of the metabolite shuttle in NADP-malic enzyme plants. In comparison with C3 species, the majority of C4 species are therefore characterised by enhanced expression and activity of alanine and aspartate aminotransferases in the photosynthetically active tissue. Both enzymes exist in multiple copies and have been found in different subcellular compartments. We tested whether different C4 species show preferential recruitment of enzymes from specific lineages and subcellular compartments. • Phylogenetic analysis of alanine and aspartate aminotransferases from a variety of monocot and eudicot C4 species and their C3 relatives was combined with subcellular prediction tools and the analysis of the according transcript amounts in mature leaves. • Recruitment of aspartate aminotransferases from a specific subcellular compartment was strongly connected to the biochemical subtype. Deviation from the main model was however observed in G. gynandra. The configuration of alanine aminotransferases was generally different in monocot and eudicot species. C4 monocots recruited an alanine aminotransferase from a specific cytosolic branch, but eudicots use alanine aminotransferase copies from a mitochondrial branch. Generally, plants display high plasticity in the setup of the C4 pathway. Beside the common models for the different C4 subtypes, individual solutions were found for plant groups or lineages.