Expression of RsPORB Is Associated with Radish Root Color.

Radish () plants exhibit varied root colors due to the accumulation of chlorophylls and anthocyanins compounds that are beneficial for both human health and visual quality. The mechanisms of chlorophyll biosynthesis have been extensively studied in foliar tissues but remain largely unknown in other tissues. In this study, we examined the role of NADPH:protochlorophyllide oxidoreductases (PORs), which are key enzymes in chlorophyll biosynthesis, in radish roots. The transcript level of was abundantly expressed in green roots and positively correlated with chlorophyll content in radish roots. Sequences of the coding region were identical between white (948) and green (847) radish breeding lines. Additionally, virus-induced gene silencing assay with exhibited reduced chlorophyll contents, verifying that is a functional enzyme for chlorophyll biosynthesis. Sequence comparison of promoters from white and green radishes showed several insertions and deletions (InDels) and single-nucleotide polymorphisms. Promoter activation assays using radish root protoplasts verified that InDels of the promoter contribute to its expression level. These results suggested that is one of the key genes underlying chlorophyll biosynthesis and green coloration in non-foliar tissues, such as roots.