Researchers have produced a tomato with three times as much b-carotene content as normal (Nature Biotechnology 2000;18:666). The genetically modified plant could be beneficial to human health as b-carotene has been shown to benefit chronic conditions such as coronary heart disease and certain cancers, say the researchers, led by Dr Peter Bramley (University of London). In addition, deficiency of b-carotene, which is a provitamin A carotenoid, can lead to blindness and premature death. The tomato plants were manipulated to contain a bacterial gene, crtI, which encodes for the enzyme phytoene desaturase and, when expressed, led to increases of b-carotene composition up to 3.5-fold. Unexpectedly, the total carotenoid level was not elevated, indicating some feedback inhibition. The modification did not affect growth or development of the tomato plant and could be passed on to subsequent generations, say the researchers.