A novel carotenoid, 4-keto-α-carotene, as an unexpected by-product during genetic engineering of carotenogenesis in rice callus

The carotenoid pathway was reconstituted and extended by genetic engineering in rice callus. In addition to astaxanthin and precursors, a novel carotenoid accumulated and was identified as 4-keto-α-carotene due to the ketolase transgene crtW.