MODULAR NATURE OF ABSCISIC-ACID (ABA) RESPONSE COMPLEXES - COMPOSITE PROMOTER UNITS THAT ARE NECESSARY AND SUFFICIENT FOR ABA INDUCTION OF GENE-EXPRESSION IN BARLEY
Qx. Shen et al., MODULAR NATURE OF ABSCISIC-ACID (ABA) RESPONSE COMPLEXES - COMPOSITE PROMOTER UNITS THAT ARE NECESSARY AND SUFFICIENT FOR ABA INDUCTION OF GENE-EXPRESSION IN BARLEY, The Plant cell, 8(7), 1996, pp. 1107-1119
The modular nature of the abscisic acid response complex (ABRC), the p
romoter unit necessary and sufficient for abscisic acid (ABA) inductio
n of gene expression in barley, is defined in this study. We investiga
ted ABA induction of a barley late embrogenesis abundant (Lea) gene, H
VA1, 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 coupli
ng element 3 (CE3). Only one copy of this ABRC is sufficient to confer
ABA induction when linked to a minimal promoter, Because we previousl
y reported another ABRC in the barley HVA22 gene, which consists of an
ACGT-box with a distal coupling element (CE1), exchange experiments w
ere conducted to study the interaction among modular elements in these
ABRCs. We show that ACGT-boxes in these ABRCs are interchangeable, in
dicating that an ACGT-box can interact with either a distal or a proxi
mal 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 dis
tal position, The presence of both the distal and the proximal couplin
g elements has a synergistic effect on the absolute level of expressio
n as well as on ABA induction, These ABRCs function in both seed and v
egetative 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 path
ways.