Abstract
Chloroplast NDH complex is a homologue of mitochondrial NADH dehydrogenase and involved in photosystem I cyclic electron transport. In higher plants, 14 subunits of the NDH complex have been identified. However, these subunits contain no electron donor-binding site and electron donor for the NDH complex also has not been decided. Arabidopsis crr1 was isolated as a mutant lacking NDH activity, using chlorophyll fluorescence imaging. Because CRR1 contains chloroplast a targeting signal and a NAD(P)H-binding motif, the CRR1 is a possible candidate for electron donor-binding subunit of the NDH complex. Interestingly, CRR1 is homologous to DHPR (dihydrodipicolinate reductase) involved in lysine biosynthesis, although it does not have DHPR activity. In addition, whereas genes for DHPR are expressed in all tissues, CRR1 is expressed only in photosynthetic tissue as well as other genes for the NDH subunits. Now we are studying the possibility that CRR1 is a subunit of the NDH complex.
