Method to improve drought tolerance in plants

A method for inhibiting or reducing light-induced stomatal opening in a plant, comprising:

• inhibiting or disabling K+in channel activity in the stomatal guard cells of the plant by expressing in the stomatal guard cells of the plant a recombinant DNA segment which encodes a plant K+in channel protein, wherein the plant K+in channel protein is KAT1, wherein the recombinant DNA segment comprises a dominant negative mutation in a codon for amino acid residue 256 or 262 of KAT1, and wherein the mutation encodes arginine at residue 256 or lysine at residue 262.

A plant having increased drought tolerance due to inhibited or disabled K+in channel activity in the stomatal guard cells of the plant, wherein the plant comprises recombinant DNA segment that encodes a plant K+in channel protein, which is expressed in the guard cells involved in stomatal opening in an amount which inhibits or disables K+in channel activity in the stomatal guard cells, wherein the plant K+in channel protein is KAT1, wherein the recombinant DNA segment comprises a dominant negative mutation in a codon for amino acid residue 256 or 262 of KAT1, and wherein the mutation encodes arginine at residue 256 or lysine at residue 262.

An expression cassette comprising a nucleic acid segment which comprises a plant KAT1 channel protein gene that comprises a dominant negative mutation operably linked to a promoter functional in a plant cell, wherein the dominant mutation is in a codon for amino acid residue 256 or 262 of KAT1, and wherein the mutation encodes arginine at residue 256 or lysine at residue 262.

A method of preparing a transformed plant in which light-induced stomatal opening is inhibited or reduced, comprising:

• (a) introducing to plant cells an expression cassette comprising a DNA segment which encodes a plant K+in channel protein, so as to yield a transformed plant, the genome of which is augmented with the expression cassette, wherein the plant K+in channel protein is KAT1, wherein the DNA segment comprises a dominant negative mutation in a codon for amino acid residue 256 or 262 of KAT1, and wherein the mutation encodes arginine at residue 256 or lysine at residue 262;
• and
• (b) identifying a transformed plant in which light-induced stomatal opening is inhibited or reduced relative to a corresponding non-transformed plant.