The transcription factor WRKY75 regulates the development of adventitious root, lateral bud and callus by modulating hydrogen peroxide content in poplar.

Hydrogen peroxide (H2O2) plays important roles in plant development. Adventitious root (AR), lateral bud (LB) and callus formation are important traits for plants. Here, a gene encoding respiratory burst oxidase homologs B (PdeRBOHB) from poplar line "NL895" (Populus. deltoides × P. euramericana) was predicted to be involved in H2O2 accumulation and its reduced expression (RE) transgenic lines were generated. H2O2 content was decreased, and the development of AR, LB and callus was inhibited, in RE PdeRBOHB lines. A gene encoding PdeWRKY75 was identified as the positive upstream transcription factor (TF) for PdeRBOHB. This regulation was confirmed by dual luciferase reporter assay, GUS transient expression analysis and electrophoretic mobility shift assay (EMSA). In the RE PdeWRKY75 lines, H2O2 content was decreased and the development of AR, LB and callus development was inhibited, while in the over expression (OE) lines, H2O2 content was increased and the development of AR and LB was inhibited, but callus formation was enhanced. Additionally, RE PdeRBOHB inhibited the expression of PdeWRKY75, while exogenous application of H2O2 showed the opposite effect. All of these results suggested that PdeWRKY75 and PdeRBOHB are part of a regulatory module in H2O2 accumulation, which is involved in the regulation of multiple biological processes.