ERN1, a novel ethylene-regulated nuclear protein of Arabidopsis

Employing differential display of mRNA to investigate the transcriptionally regulated part of the ethylene response pathway in etiolated seedlings of Arabidopsis thaliana, a novel ethylene-regulated nuclear-localized protein, designated ERN1, was identified. ERN1 is one of four genes whose differential expression was confirmed by RNA blot analysis. ERN1 is represented by a single-copy gene in the Arabidopsis genome. Its expression is suppressed by ethylene in wild-type Arabidopsis but not in the ethylene-insensitive etr1-1 mutant. To gain first insight into the biological role of ERN1, a promoter-beta -glucuronidase (GUS) gene fusion was constructed and the expression in various organs from early to late developmental stages was examined. The analysis revealed spatial and temporal expression patterns that correlate with developmental processes known to be affected by ethylene. Evidence is given that the level of expression of ERN1 is regulated through the ethylene signal transduction pathway via CTR1 and EIN3, indicating that ERN1 acts downstream of EIN3.