Constitutive expression of the neutral PR-5 (OLP, PR-5d) gene in roots and cultured cells of tobacco is mediated by ethylene-responsive cis-element AGCCGCC sequences

The constitutive accumulation of tobacco neutral PR-5 (osmotin-like protein; OLP, PR-Sd) in roots and cultured cells was studied in transgenic tobacco plants harboring the OLP promoter::GUS gene. This construct showed strong beta-glucuronidase expression in vascular tissues and cortex of roots as well as in cultured cells. Analysis using a mutated promoter showed that ethylene-responsive elements (AGCCGCC) were necessary for constitutive expression in roots and cultured cells. An electrophoretic mobility shift assay indicated that ERF3 (EREBP3), an ethylene-responsive-element-binding factor that was reported to be expressed in roots and in cultured cells as well as in ethephon-treated leaves, could bind to the AGCCGCC sequences of the OLP gene. These findings suggest that AGCCGCC sequences and ERFs mediate the constitutive expression of the OLP gene in roots and cultured cells of tobacco.