Abstract
Arabidopsis ENHANCER OF SHOOT REGENERATION (ESR) 1 and ESR2 are thought to play critical roles in in vitro shoot regeneration. In this study, we investigated the relationship between ESR1/ESR2 expression and shoot formation during in vitro shoot regeneration using ESR1::GFP and ESR2::CFP constructs. ESR1 initially expressed 1 day after trasfer onto shoot-inducing medium (SIM) whereas ESR2 initiated to express on day 4. ESR1 expression occurred prior to shoot formation and the expression continued during early stages of shoot formaion. ESR1 and ESR2 expressed in shoot apical meristem-like structures. These results suggest that ESR1 may act on commitment to shoot differentiation and ESR1 and ESR2 are involved in early events of shoot formation.
We also examined ESR2 transcript levels when translocation of ESR1 to nuclei was induced. Treatment of an inducer of expression increased ESR2 transcript levels approximately 2.9-fold higher. Howerever, application of cycloheximide inhibited upregulation of ESR2 transcripts. These results suggest that ESR1 upregulates ESR2 expression, although the upregulation is indirect.
