Functional analysis of CqPORB in the regulation of chlorophyll biosynthesis in Chenopodium quinoa

Protochlorophyllide oxidoreductase (POR) plays a key role in catalyzing the light-dependent reduction of protochlorophyllide (Pchlide) to chlorophyllide (Chlide), and thus promotes the transit from etiolated seedlings to green plants. In this study, by exploring ethyl methanesulfonate (EMS)-mediated mutagenesis in NL-6 variety, we identified a mutant that displays faded green leaf and reduced chlorophyll (Chl) and carotenoid contents. Bulk segregant analysis (BSA) revealed that a mutation in gene is genetically associated with the faded green leaf of the mutant. Further study indicates that the mutant exhibits abnormal grana stacks and compromised conversion of Pchlide to Chlide upon illumination, suggesting the important role of in producing photoactive Pchlide. Totally three isoforms, including , , and are identified in NL-6 variety. Transcriptional analysis shows that the expression of all these three isoforms is regulated in light- and development-dependent manners, and in mature quinoa plants only isoform is predominantly expressed. Subcellular localization analysis indicates that CqPORB is exclusively localized in chloroplast. Together, our study elucidates the important role of CqPORB in the regulation of Chl biosynthesis and chloroplast development in quinoa.