A Distal ABA Responsive Element in <i>AtNCED3</i> Promoter Is Required for Positive Feedback Regulation of ABA Biosynthesis in Arabidopsis

<div><p>The plant hormone abscisic acid (ABA) plays a crucial role in plant development and responses to abiotic stresses. Recent studies indicate that a positive feedback regulation by ABA exists in ABA biosynthesis in plants under dehydration stress. To understand the molecular basis of this regulation, we analyzed the <i>cis</i>-elements of the <i>AtNCED3</i> promoter in Arabidopsis. <i>AtNCED3</i> encodes the first committed and highly regulated dioxygenase in the ABA biosynthetic pathway. Through delineated and mutagenesis analyses in stable-transformed Arabidopsis, we revealed that a distal ABA responsive element (ABRE: GGCACGTG, -2372 to -2364 bp) is required for ABA-induced <i>AtNCED3</i> expression. By analyzing the <i>AtNCED3</i> expression in ABRE binding protein ABF3 over-expression transgenic plants and knock-out mutants, we provide evidence that the ABA feedback regulation of <i>AtNCED3</i> expression is not mediated by ABF3.</p>