Modular Nature of Abscisic Acid (ABA) Response Complexes: Composite Promoter Units That Are Necessary and Sufficient for ABA Induction of Gene Expression in Barley

Abstract

The modular nature of the abscisic acid response complex (ABRC), the promoter unit necessary and sufficient for abscisic acid (ABA) induction of gene expression in barley, is defined in this study. We investigated ABA induction of a barley late embrogenesis abundant (Lea) gene, HVA1, and found that the ABRC of this gene consists of a 10-bp box with an ACGT core (ACGT-box) and the 11 bp directly upstream, named coupling element 3 (CE3). Only one copy of this ABRC is sufficient to confer ABA induction when linked to a minimal promoter. Because we previously reported another ABRC in the barley HVA22 gene, which consists of an ACGT-box with a distal coupling element (CE1), exchange experiments were conducted to study the interaction among modular elements in these ABRCs. We show that ACGT-boxes in these ABRCs are interchangeable, indicating that an ACGT-box can interact with either a distal or a proximal coupling element to confer ABA response. However, the two coupling elements are not fully exchangeable. Although CE3 can function either proximal or distal to the ACGT-box, CE1 is only functional at the distal position. The presence of both the distal and the proximal coupling elements has a synergistic effect on the absolute level of expression as well as on ABA induction. These ABRCs function in both seed and vegetative tissues. In seeds, ABA induction of the ABRC containing the proximal CE3, but not the ABRC with the distal CE1, is enhanced in the presence of the transcription regulator Viviparous1, indicating that these two ABRCs are mediated by different ABA signal transduction pathways.

Regulation of Leaf Starch Degradation by Abscisic Acid Is Important for Osmotic Stress Tolerance in Plants

“…CE3-like motifs are found in the promoters of many ABAresponsive genes, often coupled to ABREs. A combination of ABRE/CE3-like motifs was initially thought to establish a minimal ABA-responsive complex to confer ABA responsiveness (Shen and Ho, 1995;Shen et al, 1996). In fact, it was later shown that the ACGT-containing ABREs and CE3 are functionally equivalent cis-acting elements and that multiple ABREs or CEs or the combination of ABREs with CEs can also confer ABA responsiveness (Hobo et al, 1999).…”

The Transcription Factors HvABI5 and HvVP1 Are Required for the Abscisic Acid Induction of Gene Expression in Barley Aleurone Cells

“…We first tested the effect of HvABI5 by itself and observed a 3-fold activation of ABRC3-GUS expression (Figure 3B), whereas the effect of ABA alone was a 19-fold enhancement. The activation of ABRC3 has been shown to be affected positively by the maize transactivator VP1 (Shen et al, 1996); thus, we also tested the effector construct 35S-VP1 . VP1 alone also gave a small activation of the reporter construct (threefold increase).…”

Gibberellins and Seed Development in Maize. I. Evidence That Gibberellin/Abscisic Acid Balance Governs Germination versus Maturation Pathways

“…overlapping cis control elements (Hattori et al, 1992;Vasil et al, 1995;Hill et al, 1996;Shen et al, 1996). No data have been published regarding possible GA-responsive negative control elements in these promoters, however, antagonistic ABA-responsive promoter elements have been identified in the GA-inducible alpha-amylase genes of other cereals (for review, see Jacobsen et al, 1995).…”