Abstract
The NAD(P)H dehydrogenase (NDH) complex mediates photosystem I cyclic and chlororespiratory electron transport. Eleven plastid-encoded and three nuclear-encoded subunits have been identified so far, but the entire subunit composition is still unknown. The Arabidopsis crr3 mutant was isolated based on its lack in NDH activity using chlorophyll fluorescence imaging. The CRR3 gene (At2g01590) encodes an unknown protein containing a putative plastid-targeting signal and a transmembrane domain. CRR3 localize to thylakoids, and is essential for the accumulation of the NDH complex. NDH complex is also required for stabilizing CRR3. These results suggest that CRR3 interacts with the NDH complex. In contrast to the other NDH subunit, CRR3 is not conserved in cyanobacteria. We propose that CRR3 is a novel subunit of the NDH complex, which is specific to chloroplasts.
