Abstract
Protein phosphorylation plays an important role in ABA-induced stomatal closure, however, little is known about the ABA signaling via protein phosphorylation in biochemical level. Previously, we found that a 61 kDa protein is phosphorylated and bound to a 14-3-3 protein in response to ABA in Vicia guard cells. In this study, we investigated ABA-induced protein phosphorylation using Arabidopsis guard cells. We found that 53 kDa and 43 kDa proteins were bound to a 14-3-3 protein in response to ABA, suggesting that ABA induced the phosphorylation of these proteins. These proteins responded to ABA at 1 μ M within a few minutes as has been found in Vicia 61 kDa protein. Furthermore, we investigated the 14-3-3 protein bindings to these two proteins using some ABA-insensitive mutant plants, including ost1/srk2e, abi1-1 and abi2-1. From these results, we report the location of these proteins in ABA signaling pathways.
