Mutants defective in chloroplast development or photosynthesis are liable to accumulate higher levels of anthocyanin in photo‐oxidative stress. However, regulatory mechanisms of anthocyanin biosynthesis in the mutants remain unclear. Here, we investigated the mechanism by which the deletion of thylakoid formation1 (THF1) leads to an increased level of anthocyanin in Arabidopsis thaliana L. Ph…