Abstract
Plant roots play important roles in absorbing water and nutrients, and in tolerance against environmental stresses. Previously, we identified a rice root-specific pathogenesis-related protein (RSOsPR10) induced by drought, salt, and wounding. RSOsPR10 expression is strongly induced by jasmonate (JA)/ethylene (ET), but suppressed by salicylic acid (SA). Here, we analyzed the promoter activity of RSOsPR10. Analyses of transgenic rice lines harboring different-length promoter::β-glucuronidase (GUS) constructs showed that the 3-kb promoter region is indispensable for JA/ET induction, SA repression, and root-specific expression. In the JA-treated 3K-promoter::GUS line, GUS activity was mainly observed at lateral root primordia. Transient expression in roots using a dual luciferase (LUC) assay with different-length promoter::LUC constructs demonstrated that the novel transcription factor OsERF87 induced 3K-promoter::LUC expression through binding to GCC-cis elements. In contrast, the SA-inducible OsWRKY76 transcription factor strongly repressed the JA-inducible and OsERF87-dependent expression of RSOsPR10. RSOsPR10 was expressed at lower levels in OsWRKY76-overexpressing rice, but at higher levels in OsWRKY76-knockout rice, compared with wild type. These results show that two transcription factors, OsERF87 and OsWRKY76, antagonistically regulate RSOsPR10 expression through binding to the same promoter. This mechanism represents a fine-tuning system to sense the balance between JA/ET and SA signaling in plants under environmental stress.