‘Golden Rice’ is a variety of rice engineered to produce bcarotene
(pro-vitamin A) to help combat vitamin A deficiency1,
and it has been predicted that its contribution to alleviating
vitamin A deficiency would be substantially improved through
even higher b-carotene content2. We hypothesized that the
daffodil gene encoding phytoene synthase (psy), one of the
two genes used to develop Golden Rice, was the limiting step
in b-carotene accumulation. Through systematic testing
of other plant psys, we identified a psy from maize that
substantially increased carotenoid accumulation in a model
plant system. We went on to develop ‘Golden Rice 2’
introducing this psy in combination with the Erwinia uredovora
carotene desaturase (crtI) used to generate the original Golden
Rice1. We observed an increase in total carotenoids of up to
23-fold (maximum 37 lg/g) compared to the original Golden
Rice and a preferential accumulation of b-carotene