Abstract
Abscisic acid (ABA) regulates physiologically important stress and developmental responses. ABI1 encodes a protein phosphatase 2C that functions in early in ABA signaling. To address the mechanism of ABI1-mediated ABA signaling, we generated tagged ABI1 Arabidopsis expression lines in an abi1 knockout mutant and performed affinity column purification of ABI1-associated proteins. Transgenic tagged ABI1 plants show a strong ABA insensitive phenotype at the seed germination stage. After silver staining, visible bands overlapped with controls, and specific bands associated with purified tagged ABI1 samples were consistently observed. Mass-spectrometrical analyses allowed identification of proteins associated with ABI1. These included some known ABA signaling components. These results suggested that our strategy has the potential of identifying ABA signaling components. We found that a sub-group of gene family members interacted with ABI1 in an ABA dependent manner. The functional relationship between ABI1 and this protein family is being characterized.
