attempted in tomato by gene suppression or overexpression with HMG-
CoA reductase or with phytoene synthase as targets, respectively (Fig-
ure 2.4). Suppression of the latter enzyme, which catalyzes the formation
of the first carotene named phytoene, may lead to tomatoes that are not
red but display a shade of yellow like certain peppers, which may be an
34 QUALITY AND BREEDING—CULTIVARS, GENETIC ENGINEERING
FIGURE 2.4Major pathway of carotenoid biosynthesis in higher plants. Routes to plant
hormones and to some potential phytochemicals are also indicated. FPP, farnesyl py-
rophosphate; GPP, geranyl pyrophosphate; GGPP, geranylgeranyl pyrophosphate;
HMG-CoA, 3-hydroxy-3-methylglutaryl-CoA; IPP, isopentenyl pyrophosphate