Genetic dissection of the abscisic acid biosynthetic pathway in maize (Zea mays L.) embryos

Metabolites in the ABA biosynthetic pathway were identified by analyzing xanthophyll profiles generated in embryos of wild-type and viviparous mutants of Zea mays L. The level of lutein differed greatly in vp8 embryos depending on whether or not elongated shoots were included in the sample. Lutein was the major xanthophyll in embryos when elongated shoots were included. However, lutein was a minor xanthophyll in vp8 embryos without elongated shoots anti in wild-type embryos. Lutein was produced mainly in the elongated shoots of viviparous mutants. No lutein epoxides were detected in mutant or wild type embryos. These results show that lutein is not a precursor of ABA in maize embryos. Accumulation of zeaxanthin combined with a reduction of epoxy-xanthophylls in vp10 suggest that this defect impairs the epoxidation of zeaxanthin. Mutant vp-92EP8 accumulated all-trans-violaxanthin, while vp-92GN24 accumulated all-trans-violaxanthin and all-trans-neoxanthin. These results imply that all-trans-neoxanthin is an intermediate between all-trans-violaxanthin and 9'-cis-neoxanthin. Under this model, vp-92EP8 prevents the conversion of all-trans-violaxanthin to all-trans-neoxanthin, while vp-92GN24 prevents the conversion of all-trans-neoxanthin to 9'-cis-neoxanthin. Accumulation of all-trans-violaxanthin, all-trans-neoxanthin and 9'-cis-neoxanthin combined with the reduction of zeaxanthin was shown in vp8. A block in the oxidative cleavage step.

Genetic dissection of the abscisic acid biosynthetic pathway in maize (Zea mays L.) embryos Academic Article