ABSCISIC-ACID AND THE DEVELOPMENTAL REGULATION OF EMBRYO STORAGE PROTEINS IN MAIZE

The relationship of abscisic acid (ABA) inhibition of precocious germination and ABA-induced storage protein accumulation was examined over the course of embryogenesis in wild-type and viviparous mutants of maize (Zea mays L.). We show that a high level of embryo ABA and the product of the Viviparous-1 gene are both required in early maturation phase for germination suppression and the accumulation of storage globulins encoded by the gene Glb 1. Suppressing precocious germination with a high osmoticum is not sufficient to initiate Glb 1 protein synthesis, although continued accumulation is contingent upon this inhibition; germination of immature or mature embryos leads to a decline in synthesis and the degradation of stored globulins. Late in embryogenesis, fragments of Glb 1 protein accumulate, coinciding with the loss of ABA sensitivity. These results suggest that ABA influences storage globulin accumulation by initiating synthesis, suppressing degradation, and inhibiting precocious germination.