Expression of an Erwinia phytoene desaturase gene not only confers multiple resistance to herbicides interfering with carotenoid biosynthesis but also alters xanthophyll metabolism in transgenic plants

Abstract

In carotenoid biosynthesis of plants, the desaturation sequence starting from phytoene is the target of many bleaching herbicides. An Erwinia uredovora phytoene desaturase gene crtl which mediates the reactions was introduced into tobacco plants by the leaf disc method, and the seedlings highly resistant to the bleaching herbicide norflurazon were selected on a medium containing 3 mu M norflurazon. These tobacco transformants produced large amounts of the Crtl protein which correlated with the crtl mRNA levels. Resistance against various bleaching herbicides or inhibitors was examined. Consequently the transgenic plant showed multiple strong resistance not only to norflurazon, fluridone, flurtamone, fluorochloridone and diflufenican, which interfere with the plant-type phytoene desaturase, but also to KM143-958, J852 and LS80707, which are inhibitors of zeta-carotene desaturase. Furthermore, carotenoid analysis of the leaves of the transgenic tobacco revealed that the composition of leaf carotenoids was changed: levels of beta-carotene and its xanthophyll metabolites, such as violaxanthin, were increased and the level of lutein, a xanthophyll derived from alpha-carotene, was reduced in the modified plant, while the total amount of carotenoids was similar between the transgenic and a control plants.