Immunomodulation of ABA function affects early events in somatic embryo development.

Immunomodulation of abscisic acid (ABA) function during somatic embryogenesis of Nicotiana plumbaginifolia has been used to demonstrate for the first time the effect of this phytohormone on early embryonic events. A homozygous transgenic line constitutively expressing an anti-abscisic acid (ABA) single chain fragment variable antibody in the endoplasmic reticulum was established. Development of somatic embryos from the transgenic line and the wild type was compared. The ABA biosynthesis mutants aba1 and aba2 and wild type cultures treated with the ABA biosynthesis inhibitor fluridone were also used for the comparative investigations. The development of embryonic structures was disturbed in the early stages of all cultures in which ABA function was blocked or which were ABA-deficient. After ABA complementation of the in vitro cell cultures normal somatic embryo development was restored.