Abstract
NAD kinase (NADK) is an only enzyme, which synthesizes NADP from NAD. Measurement of photosynthetic parameters of the nadk2 mutant, which is defective in chloroplast NADK, revealed that the effective efficiency of photosynthetic electron transport was decreased and non-photochemical quenching was increased. We therefore quantified xanthophylls and the xanthophyll composition was aberrant in nadk2 mutant. Furthermore, we investigated carbon and nitrate metabolism in nadk2 mutant and NADK2-overexpressing plant (OX). Carbohydrate levels were decreased in nadk2, while that were increased in OX. Likewise, the amounts of glutamate and related amino acids were also paralleled the expression level of NADK2. These results suggest that overexpression of NADK2 activates both carbon fixation and nitrate assimilation, and NADK2 is essential for regulation of chloroplast-specific function.
