https://orcid.org/0000-0003-4314-6555
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ABSTRACT
Arabidopsis NADK2 (NAD kinase 2) is a chloroplast-localized enzyme involved in NADP+ synthesis, which acts as the final electron acceptor in the photosynthetic electron transfer chain. The NADK2-deficient mutant (nadk2) was used to analyze the effect of NAD(P)(H) unbalance in the dark-induced leaf senescence. During senescence, WT plants and nadk2 mutants showed a similar reduction in chlorophyll content. NAD(P)(H) quantification showed that the amount of total NAD(P)(H) decreased on the day 7 in WT but on the day 3 in nadk2. The phosphorylation ratio (i.e. NADP(H)/NAD(H)) decreased on day 1 in WT. In contrast, the nadk2 showed lower phosphorylation ratio at 0 day and no change throughout the aging process. Metabolome analysis showed that the metabolic profiles of both WT plants and nadk2 mutants subjected to dark-induced senescence adopted similar patterns as the senescence progressed. However, the changes in individual metabolites in the nadk2 mutants were different from those of the WT during dark-induced senescence.
Acknowledgments
We thank Ms. Yanhui Zu for technical assistance.
Disclosure statement
No potential conflict of interest was reported by the authors.
Abbreviations
| CE-MS | = | capillary electrophoresis-mass spectrometry |
| DHAP | = | dihydroxyacetone phosphate |
| F6P | = | fructose 6-phosphate |
| G1P | = | glucose-1-phosphate |
| G-3-P | = | glycerol 3-phosphate |
| G6P | = | glucose-6-phosphate |
| HCA | = | hierarchical clustering analysis |
| NADP+ | = | nicotinamide adenine dinucleotide phosphate |
| NAD+ | = | nicotinamide adenine dinucleotide |
| PCA | = | Principal component analysis |
| PEP | = | phosphoenolpyruvate |
| 3PGA | = | 3-phosphoglycerate |
| R5P | = | ribose-5-phosphate |
| RuBP | = | ribulose-1,5-bisphosphate |
| Ru5P | = | ribulose-5-phosphate |
| S7P | = | sedoheptulose-7-phosphate |
| TCA | = | tricarboxylic acid |
| WT | = | wild type |
Author contribution statement
Chaomurilege: Evaluated the data, carried out the experiments, and authored the manuscript.
Atsuko Miyagi: Conducted the metabolome analysis.
Toshiki Ishikawa: Evaluated the information.
Masatoshi Yamaguchi: Evaluated the information.
Hideki Murayama: Designed the metabolome analysis.
Maki Kawai-Yamada: Conceived the research project, analyzed the data, and authored the manuscript. On the findings and the manuscript, each author offered their thoughts.