Hypersensitive ABA receptors having modified PP2C-binding interfaces

A non-naturally occurring isolated mutant nucleic acid comprising a polynucleotide encoding a mutated PYR/PYL receptor polypeptide comprising one or more amino acid substitutions in a type 2 protein phosphatase (PP2C) binding interface at a position corresponding to K63, I82, I84, D154, M158, T162, L166, or K170 in the PYR1 polypeptide as set forth in SEQ ID NO:1, wherein the mutated PYR/PYL receptor polypeptide inhibits the activity of a PP2C polypeptide in the presence of abscisic acid (ABA) to a greater extent than a wild-type control PYR/PYL receptor polypeptide in the presence of the same concentration of ABA, wherein the mutated PYR/PYL receptor polypeptide does not inhibit the activity of the PP2C polypeptide in the absence of said ABA, wherein the mutated PYR/PYL receptor polypeptide comprises one or more amino acid substitutions corresponding to the amino acid substitution K63E, I82A/F/K/S, I84A/D/N/R/S/T, D154G/H/K/Q/R/W, M158G/W, T162H/K/L/M/W, L166A/G/K/M/N/R/S/T/W, or K170A/D/E/G/M/N/Q/R/T/V/Y in the PYR1 polypeptide as set forth in SEQ ID NO:1, and wherein the mutated PYR/PYL receptor polypeptide has at least 95% amino sequence identity to the amino acid sequence as set forth in SEQ ID NO:70.