Rice (Oryza sativa), a major staple food, is usually milled to remove the oil-rich aleurone layer that turns rancid upon storage, especially in tropical areas.  The remaining edible part of rice grains, the endosperm, lacks several essential nutrients, such as provitamin A.  Thus, predominant rice consumption promotes vitamin A deficiency, a serious public health problem in at least 26 countries, including highly populated areas of Asia, Africa and Latin America.  Recombinant DNA technology was used to improve its nutritional value in this respect.  A combination of transgenes enabled biosynthesis of provitamin A in the endosperm.