Transcriptional regulator AtET2 is required for the induction of dormancy during late seed development

Abstract

During the late stages of seed development, the embryo patterning program is completed and maturation is initiated. One of the main events during the maturation phase is the acquisition of dormancy, characterized by the failure of a normally developed seed to germinate precociously. Dormancy is controlled by a complex regulatory mechanism that involves the phytohormone gibberellin (GA) and the transcription factor FUSCA3 (FUS3). Here, we demonstrate the importance of the previously characterized GA regulator EFFECTOR OF TRANSCRIPTION2 (AtET2) for correct seed development. We show that entering the maturation phase, seeds of the et2-1 mutant, which contain a non-functional AtET2 gene, fail to induce dormancy. This correlates well with the observed activity pattern of the AtET2 promoter, which is active in the maturing embryo. AtET2 action during seed development is dependent on a complex interaction with GA and the FUS3 gene, the latter evidenced by the phenotypes of the et2-1 fus3-T double mutant. We show that in vitro expressed AtET2 protein can bind to both linear and supercoiled DNA without any obvious sequence preference. This suggests that, within a larger protein complex, AtET2 might be required for the correct positioning upon the DNA.