Host: The Japanese Society of Plant Physiologists
Pages 0297
Chloroplast NAD kinase enhances carbon and nitrogen metabolism
Chloroplast NAD kinase (NADK2) has been identified as an essential enzyme for chlorophyll synthesis, photosynthetic electron transport, and xanthophyll cycle. Metabolite analysis revealed that the contents of intermediates of the Calvin cycle were increased in transgenic plants overexpressing NADK2 gene (NADK2-OX). The activities of RubisCO and glyceraldehyde-3-phosphate dehydrogenase as well as CO2 uptake were also increased, indicating that carbon fixation was enhanced in NADK2-OX. On the other hand, the accumulation of free amino acids, especially glutamine and glutamate were observed in NADK2-OX. Furthermore, the expression levels of chloroplast glutamine synthetase and NADH-dependent glutamate synthase genes were increased. The uptake and reduction process of nitrate were also increased. It therefore seemed that the activation of GS/GOGAT pathway and nitrate reduction contributed to amino acid overproduction. These results indicate that NADK2 overexpression enhances both carbon and nitrate metabolism.
