Gibberellin Induces an Increase in Cytosolic Ca2+ via a DELLA-Independent Signaling Pathway

DELLA proteins play a central role in gibberellin (GA) signaling. GA triggers DELLA degradation via the ubiquitin-proteasome pathway, thereby promoting plant growth. An increase in cytosolic Ca 2+ ([Ca 2+ ] cyt ) was observed previously after several hours of GA application. Recent studies also suggest the existence of a DELLA-independent GA response. However, the effect of DELLA on the GA-induced increase in [Ca 2+ ] cyt remains unknown. This study reexamined the effects of GAs on [Ca 2+ ] cyt using the Ca 2+ sensor protein aequorin in Arabidopsis ( Arabidopsis thaliana ). [Ca 2+ ] cyt increased within a few minutes of GA treatment, even in transgenic plants expressing a mutated degradation-resistant version of REPRESSOR OF ga1-3 and in della pentuple mutant plants. In addition, it was also revealed that Ca 2+ is not involved in DELLA degradation. These results suggest that the GA-induced increase in [Ca 2+ ] cyt occurs via a DELLA-independent pathway, providing important information on the GA signaling network.