Interactions of Two Transcriptional Repressors and Two Transcriptional Activators in Modulating Gibberellin Signaling in Aleurone Cells  

Abstract

Gibberellins (GAs) regulate many aspects of plant development, such as germination, growth, and flowering. The barley (Hordeum vulgare) Amy32b a-amylase promoter contains at least five cis-acting elements that govern its GA-induced expression. Our previous studies indicate that a barley WRKY gene, HvWRKY38, and its rice (Oryza sativa) ortholog, OsWRKY71, block GA-induced expression of Amy32b-GUS. In this work, we investigated the functional and physical interactions of HvWRKY38 with another repressor and two activators in barley. HvWRKY38 blocks the inductive activities of SAD (a DOF protein) and HvGAMYB (a R2R3 MYB protein) when either of these proteins is present individually. However, SAD and HvGAMYB together overcome the inhibitory effect of HvWRKY38. Yet, the combination of HvWRKY38 and BPBF (another DOF protein) almost diminishes the synergistic effect of SAD and HvGAMYB transcriptional activators. Electrophoretic mobility shift assays indicate that HvWRKY38 blocks the GA-induced expression of Amy32b by interfering with the binding of HvGAMYB to the cis-acting elements in the a-amylase promoter. The physical interaction of HvWRKY38 and BPBF repressors is demonstrated via bimolecular fluorescence complementation assays. These data suggest that the expression of Amy32b is modulated by protein complexes that contain either activators (e.g. HvGAMYB and SAD) or repressors (e.g. HvWRKY38 and BPBF). The relative amounts of the repressor or activator complexes binding to the Amy32b promoter regulate its expression level in barley aleurone cells.

A negative regulator encoded by a rice WRKY gene represses both abscisic acid and gibberellins signaling in aleurone cells

“…They can be bound by different groups of transacting factors. W-box could be bound by WRKY-type transcription factors (Rushton et al 1995;Zhang et al 2004;Zou et al 2008); pyrimidine box could be bound by DOF proteins (Washio 2003;Diaz et al 2005;MorenoRisueno et al 2007); transactivator GAMYB has been shown to bind to GARE (Gubler et al 1995;Zou et al 2008); and another cis-acting element Amy box could be bound by 1R domain MYB proteins (Lu et al 2002). So far, no trans-acting factor has been shown to bind to the DAE box.…”

The WRKY6 Transcription Factor ModulatesPHOSPHATE1Expression in Response to Low Pi Stress inArabidopsis

“…Petroselinum crispum WRKY1 has been shown to bind to the W-box of its native promoter as well as to that of Pc WRKY3 and Pc PR1-1 based on chromatin immunoprecipitation (ChIP) analysis (Turck et al, 2004). Candidate target genes for At WRKY53 were identified with a pull-down assay (Miao et al, 2004), and electrophoretic mobility shift assays identified candidate targets for Hordeum vulgare WRKY transcription factor WRKY38 (Zou et al, 2008), Arabidopsis WRKY26 and WRKY11 (Ciolkowski et al, 2008), Nicotiana tabacum WRKY1, WRKY2, and WRKY4 (Yamamoto et al, 2004), and O. sativa WRKY71 (Zhang et al, 2004).…”

Cotton WRKY1 Mediates the Plant Defense-to-Development Transition during Infection of Cotton byVerticillium dahliaeby ActivatingJASMONATE ZIM-DOMAIN1Expression

“…HvWRKY1/38 is a key regulator of cold and drought responses, immune response, and seed germination (Marè et al, 2004;Shen et al, 2007;Zou et al, 2008). OsWRKY13 is involved in plant resistance to bacterial infection and responds to drought stress by selectively binding to different target genes (Deng et al, 2012b;Xiao et al, 2013).…”