Abstract
The chloroplastic NAD(P)H dehydrogenase (NDH) plays a role in cyclic electron flow around photosystem I to produce ATP, especially for adapting to environmental changes. While NDH contains 11 subunits that are homologous to the subunits of prokaryotic respiratory complex I (EC 1.6.5.3) and 3 subunits that are unique in chloroplastic and cyanobacterial NDH, subunits that serve as electron input device are not yet unidentified. To isolate the unidentified subunits, we performed the phylogenetic profiling and selected 37 Arabidopsis proteins as potential candidates for NDH subunits. Further characterization of T-DNA insertion mutants indicated that knockout of two ndh-gene-candidates actually impaired the NDH-dependent increase in chlorophyll fluorescence and drastically decreased the amounts of NDH complex. We discuss the possibility of two proteins as the novel NDH subunits.
