A REGULATORY ROLE FOR THE ABI3 GENE IN THE ESTABLISHMENT OF EMBRYO MATURATION IN ARABIDOPSIS-THALIANA

The AB13 gene product of Arabidopsis is essential for correct completi on of seed maturation. A severe mutant allele at this locus results in seed that remain green, fail to establish desiccation tolerance, and that germinate at a developmental stage when wild-type seed will not, Moreover, the formation of leaf primordia and xylem differentiation, b oth characteristic of germinating wildtype seedlings, can be observed in embryos harvested 12 days after flowering, Thus, mature abi3 embryo s reach a developmental state that more closely resembles the characte r of a developing seedling rather than that of a dormant embryo. Previ ous studies of this gene have resulted in the suggestion that ABI3 is a transducer of abscisic acid induced seed dormancy, Our results demon strate that the ABI3 gene product can be most accurately described as one of the major regulators of the transition between embryo maturatio n and early seedling development, rather than simply a transducer of t he abscisic acid signal.