SEED-SPECIFIC IMMUNOMODULATION OF ABSCISIC-ACID ACTIVITY INDUCES A DEVELOPMENTAL SWITCH

A single-chain Fv antibody (scFv) gene, which has previously been used to immunomodulate abscisic acid (ABA) activity in transgenic tobacco to create a 'witty' phenotype, was put under control of the seed-speci fic USP promoter from Vicia faba and used to transform tobacco, Transf ormants were phenotypically similar to wild-type plants apart from the ir seeds, Anti-ABA scFv embryo development differed markedly from wild -type embryo development, Seeds which accumulated similar levels of a scFv that binds to oxazolone, a hapten absent from plants, developed l ike wild-type embryos, Anti-ABA scFv embryos developed green cotyledon s containing chloroplasts and accumulated photosynthetic pigments but produced less seed storage protein and oil bodies, Anti-ABA scFv seeds germinated previously if removed from seed capsules during developmen t but were incapable of germination after drying, Total ABA levels wer e higher than in wild-type seeds but calculated free ABA levels were n ear-zero until 21 days after pollination, We show for the first time s eed-specific immunomodulation and the resulting switch from the seed m aturation programme to a germination programme, We conclude that the i mmunomodulation of hormones can alter the development programme of tar get organs, allowing the study of the directly blocked endogenous mole cules and manipulation of the system concerned.