Flooding-Induced Sensitisation to Ethylene in Rumex Palustris and the Possible Involvement of a Putative Ethylene Receptor Gene

Abstract

Rumex palustris, a flooding tolerant plant, increases the petiole elongation rate in response to complete submergence. This response can be partly mimicked by enhanced ethylene levels and low oxygen concentrations. A cDNA homologous to the ethylene-response sensors (ERS/ETR1) from Arabidopsis thaliana was isolated from a R. palustris cDNA library. This cDNA, RP-ERS1, was 242lbp long and shared 66% nucleotide homology with ETR1 and ERS in their coding regions. The expression level of RP-ERS1 was induced by exposing plants to 3% oxygen and an increase in mRNA concentration could be detected 20 minutes after the beginning of the treatment, preceding the first significant increase in elongation that was observed after 40 to 50 minutes. Experiments with ethylene synthesis and action inhibitors demonstrated that a functioning ethylene signaling pathway is necessary for the stimulation of the petiole elongation rate by low oxygen concentrations. These results suggest that the regulation of the RP-ERSI gene plays a role in the strength of the petiole elongation response R. palustris plants upon flooding.