Abstract
Dark-operative protochrolophyllide reductase (DPOR) is a nitrogenase-like enzyme consisting of three subunits, ChlL, ChlN and ChlB, and plays a critical role in chlorophyll (Chl) biosynthesis in the dark. While nitrogenase is distributed only among some prokaryotes, there has been no direct evidence for functional operation of nitrogenase-like enzyme in any eukaryotes. Here we report functional expression of probable DPOR components encoded by the chloroplast genome of Physcomitrella patens in the cyanobacterium Leptolyngbya boryana. We constructed two shuttle vectors for overexpression of two DPOR components, ChlL and ChlN-ChlB from P. patens, and introduced them into the cyanobacterial mutants lacking chlL and chlB. Both transformants restored the ability of Chl biosynthesis in the dark, indicating that these chloroplast genes encode functional DPOR subunits and that each DPOR component is compatible between P. patens and L. boryana. This compatibility was also confirmed by in vitro reconstitution with purified ChlL and ChlN-ChlB.
