The present invention relates to the DNA sequence for eukaryotic genes encoding .epsilon. cyclase isolated from romaine lettuce as well as vectors containing the same and hosts transformed with said vectors. The present invention provides methods for controlling the ratio of various carotenoids in a host and to the production of novel carotenoid pigments. The present invention also provides a method for treating disease by administering carotenoids obtained from transformed hosts, or by administering a composition containing the transformed hosts.