Characterization of Carotenoid Biosynthetic Pathway Using Viviparous Mutant Embryos in Maize(Zea mays L.)

Carotenoid compounds in embryos of wild-type(WT) and viviparous mutants of maize(Zea mays L.) were analyzed using high performance liquid chromatography(HPLC) with a photodiode array detector. Zeaxanthin accumulates in WT embryos as the major carotenoid. Phytoene accumulates in vp2 and 1p5, phytofluene in 3. and S-carotene in the rpg mutant embryos. This indicates that the vp2 and vp5 mulants impair phytoene desaturase from 15-cis-phytoene to 15-cis-phytofluene. The 113 mutant has neither an isomerase from 15-cis-phytofluene to all-trans-phytofluene nor phytofluene desaturase from phytofluene 10 S-carotene, The vp9 mutant does not have the &-carotene desaturase from $-carotene to lycopene. Our analysis shows that the terminal carotenoid, y-carotenet B, Y-carotene), accumulates in the vp7 mutant embryos. The E-carotene(e. E-carotene), a product of ô-carotene(, Y -carotene) in some plants, however, has not been found in maize embryos, The vp7 mutant impairs a cyclization step from y-carotene to both B-carotene and a-carotene. We suggest that monocyclic y-carotene is the sole precursor of both bicyclic ß-carotenel B. B-carotene) and a carotenel B,？？-carotene) in maize.