Abstract
We isolated Arabidopsis ABA hypersensitive mutants using ABA analog. One of these mutants, ahg3 is analyzed in this study. This mutant exhibits less germination or growth activities at the presence of ABA. Characterization of ahg3 revealed that ahg3 have enhanced sensitivity to salinity and osmotic stress. We conducted mapping of ahg3 and identified a point mutation in the AtPP2CA gene that encodes a PP2C. In vitro PP2C activity of the recombinant ahg3-1 protein was hundred times lower than that of wild type protein. ahg3-2, a T-DNA insertion mutant, showed ABA hypersensitive phenotype similar to ahg3-1. We compared the ABA sensitivity of ahg3-2 with that of other T-DNA insertion mutants of ABA-related PP2Cs. ahg3-2 showed the strongest phenotype at post-germination growth phase. This result indicates that among several PP2Cs that are implicated in ABA response, AHG3/AtPP2CA may play a major role in the ABA signaling pathway at germination and post-germination growth.
