Synthetic conversion of leaf chloroplasts into carotenoid-rich plastids reveals mechanistic basis of natural chromoplast development

Significance Carotenoids are natural pigments whose properties as provitamin A and health-promoting phytonutrients make them ideal targets for biofortification. Here, we show that plastids specialized in carotenoid overaccumulation named chromoplasts can be synthetically produced in plant tissues that do not naturally develop them. We further demonstrate that differentiation of chromoplasts from leaf chloroplasts not just causes but requires both a reduction in photosynthetic activity and a stimulation of carotenoid biosynthesis in a process hardwired to a major reprogramming of global gene expression and cell metabolism. The synthetic system that we report here should allow to boost the nutritional quality of green vegetables and forage crops once their photosynthetic activity is dispensable (e.g., just before harvesting).