Abstract
There are two structurally unrelated protochlorophyllide (Pchlide) reductases in photosynthetic organisms; one is dark-operative reductase (DPOR) and the other is light-dependent reductase (LPOR). Since angiosperms employ LPOR as the sole Pchlide reductase, seedlings in the dark accumulate Pchlide that binds to LPOR to form prolamellar body (PLB) characterized by a unique paracrystalline structure in etiolplasts. However, it is unclear if LPOR has an intrinsic property to form PLB and how LPOR have evolved to form PLB during evolution. Here we show aberrant structure formation by overexpression of a cyanobacterial LPOR in a mutant lacking DPOR of the cyanobacterium Leptolyngbya boryana. We isolated a transformant overexpressing the L. boryana LPOR. Aberrant structures apparently different from thylakoid were observed in the dark grown cells by electron microscopy. LPOR localization in the aberrant structures is supported by immunocytochemical microscopy with anti-LPOR antiserum. Further cellular and biochemical analysis suggested that the cyanobacterial LPOR forms the aberrant structures but fails to form a photoactive complex.
