Using cassava to address vitamin A deficiency

 ‘A natural variation shows promise for increasing provitamin A in cassava roots using transgenic or conventional methods’

 Cassava is an important food source in many poverty-stricken regions of the world, including sub-Saharan Africa, but the low levels of micronutrients in commercial varieties do little to address hidden hunger. New research published in The Plant Cell shows that a single, naturally arising change in one gene leads to high provitamin A levels in cassava roots and opens the door to addressing vitamin A deficiency via biofortified cassava.

 An article published in The Plant Cell this week describes the results of a collaborative effort led by Professor Peter Beyer from Freiberg University in Germany, together with researchers at the International Center for Tropical Agriculture (CIAT) in Colombia. These researchers studied a naturally arising variant of cassava with yellow roots in order to understand the synthesis of provitamin A carotenoids, dietary precursors of vitamin A. Beyer was also co-creator of Golden Rice, a biofortified crop which provides precursors of vitamin A not usually present in the rice that people eat.

 In this work, the scientists compared different cassava cultivars with white, cream, or yellow roots - more yellow corresponding to more carotenoids - in order to determine the underlying causes of the higher carotenoid levels found in the rare yellow-rooted cassava cultivar. They tracked the difference down to a single amino acid change in the enzyme phytoene synthase, which functions in the biochemical pathway that produces carotenoids. The authors went on to show that the analogous change in phytoene synthases from other species also results in increased carotenoid synthesis, suggesting that the research could have relevance to a number of different crop plants. Furthermore, they were able to turn a white-rooted cassava cultivar into a yellow-rooted plant that accumulates beta-carotene (provitamin A) using a transgenic approach that increased the enzyme phytoene synthase in the root.

 This work beautifully combines genetics with biochemistry and molecular biology to deepen our understanding of carotenoid biosynthesis. “It paves the way for using transgenic or conventional breeding methods to generate commercial cassava cultivars containing high levels of provitamin A carotenoids, by the exchange of a single amino acid already present in cassava” says Beyer. Thus, it has the potential be a big step the battle against vitamin A deficiency, which is estimated to affect approximately one third of the world’s preschool age children.