Dihydrodipicolinate reductase (DHPR)-like protein that may not function as DHPR in lysine biosynthesis (PubMed:15652176, PubMed:17727612). Required for both formation and activity of the chloroplast NAD(P)H dehydrogenase (NDH) complex of the photosynthetic electron transport chain. May function in assembly or stabilization of the NDH complex (PubMed:17727612). Expressed specifically in leaves. Impaired chloroplastic NAD(P)H dehydrogenase (NDH) activity, probably due to a reduced stability of the NDH complex. Unlike DAPB1 and DAPB2, DAPB3 is unable to complement an E.coli dapB strain. Belongs to the DapB family.