Figure 3.

PP2C activity is required for ABI1 function as a negative regulator in ABA signaling. (A) The sequences and locations of three ABI1 mutations in the PP2C domain are shown. (B) ABI1 mutations did not affect protein expression as shown after [³⁵S]methionine labeling, immunoprecipitation, and SDS/PAGE. (C) Etiolated maize mesophyll protoplasts were electroporated with the reporter gene HVA1-LUC with an inert construct or with different ABI1 constructs: wild-type ABI1 (WT), MED141–143IGH mutation (MED), G174D mutation (G), and DGH177–179KLN mutation (DGH). Transfected cells were incubated without or with ABA (100 μM) for 16 h to observe the maximal effect on ABA-inducible transcription. PP2C activity was measured from transfected maize mesophyll protoplast (D) and transformed E. coli cells (E).