Heat resistant plants and plant tissues comprising a variant adenosine diphosphate glucose pyrophosphorylase small subunit protein and methods of use thereof

1. A polynucleotide encoding a mutant plant AGPase small subunit protein, or a functional fragment of said protein, said protein comprising an amino acid mutation wherein the amino acid corresponding to the threonine amino acid at position 462 of wild type maize endosperm AGPase small subunit protein is replaced by an amino acid that confers increased heat stability when said mutant AGPase small subunit is expressed to form an AGPase enzyme, wherein said fragment comprises said amino acid mutation at position 462 and wherein said fragment provides for said increased heat stability when said fragment is expressed to form an AGPase enzyme, wherein said replacement amino acid that confers increased heat stability is an isoleucine.

2. The polynucleotide according to claim 1 , wherein said mutant AGPase small subunit is a maize endosperm AGPase small subunit.

3. The polynucleotide according to claim 1 , wherein said mutant plant AGPase small subunit protein encoded by said polynucleotide comprises the amino acid sequence shown in any one of SEQ ID NO: 2, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 21, SEQ ID NO: 22, SEQ ID NO: 23, SEQ ID NO: 24, or SEQ ID NO: 25, or a functional fragment thereof, wherein said fragment comprises said replacement amino acid at position 462 and wherein said fragment provides for said increased heat stability when said fragment is expressed to form an AGPase enzyme.

4. The polynucleotide according to claim 1 , wherein said polynucleotide comprises the nucleotide sequence shown in any one of SEQ ID NO: 1, SEQ ID NO: 11, SEQ ID NO: 12, or SEQ ID NO: 13, or a functional fragment thereof, wherein said fragment encodes an amino acid sequence comprising said amino acid mutation at position 462 and wherein said fragment provides for said increased heat stability when said fragment is expressed to form an AGPase enzyme.

5. A polynucleotide encoding a chimeric plant AGPase small subunit protein, or a functional fragment of said protein, wherein said chimeric AGPase protein comprises an N-terminus sequence from an N-terminus region of a plant AGPase small subunit from a first plant and a C-terminus sequence from a C-terminus region of a plant AGPase small subunit from a second plant, and said chimeric plant AGPase small subunit protein comprises an amino acid mutation wherein the amino acid corresponding to the threonine amino acid at position 462 of wild type maize endosperm AGPase small subunit protein is replaced by an amino acid that confers increased heat stability when said mutant AGPase small subunit is expressed to form an AGPase enzyme, wherein said fragment encodes an amino acid sequence comprising said amino acid mutation at position 462 and wherein said fragment provides for said increased heat stability when said fragment is expressed to form an AGPase enzyme, wherein said replacement amino acid that confers increased heat stability is an isoleucine.

6. The polynucleotide according to claim 5 , wherein said N-terminus sequence comprises the first 150 to 250 amino acids of the N-terminus region of said subunit of AGPase of said first plant and said C-terminus sequence comprises the terminal 300 residues or less of the C-terminus region of said subunit of AGPase of said second plant, wherein said C-terminus comprises at least the replacement amino acid relative to position 462 of a wild type maize endosperm AGPase small subunit protein.

7. The polynucleotide according to claim 5 , wherein said N-terminus region is from maize endosperm small subunit of AGPase and/or said C-terminus region is from potato tuber small subunit of AGPase.

8. The polynucleotide according to claim 5 , wherein said plant AGPase small subunit protein encoded by said polynucleotide comprises the amino acid sequence shown in any of SEQ ID NO: 4, SEQ ID NO: 8, SEQ ID NO: 9, or SEQ ID NO: 10, or a functional fragment thereof, wherein said fragment comprises said replacement amino acid at position 462 and wherein said fragment provides for said increased heat stability when said fragment is expressed to form an AGPase enzyme.

9. The polynucleotide according to claim 5 , wherein said polynucleotide comprises the nucleotide sequence shown in any of SEQ ID NO: 3, SEQ ID NO: 14, SEQ ID NO: 15, or SEQ ID NO: 16, or a functional fragment thereof, wherein said fragment encodes an amino acid sequence comprising said amino acid mutation at position 462 and wherein said fragment provides for said increased heat stability when said fragment is expressed to form an AGPase enzyme.

10. A protein comprising:

a) a polypeptide encoded by a polynucleotide encoding a mutant plant AGPase small subunit protein, or a functional fragment of said protein, said protein comprising an amino acid mutation wherein the amino acid corresponding to the threonine amino acid at position 462 of wild type maize endosperm AGPase small subunit protein is replaced by an amino acid that confers increased heat stability when said mutant AGPase small subunit is expressed to form an AGPase enzyme, wherein said fragment comprises said amino acid mutation at position 462 and wherein said fragment provides for said increased heat stability when said fragment is expressed to form an AGPase enzyme, wherein said replacement amino acid is isoleucine; or

b) a polypeptide encoded by a polynucleotide encoding a chimeric plant AGPase small subunit protein, or a functional fragment of said protein, wherein said chimeric AGPase protein comprises an N-terminus sequence from an N-terminus region of a plant AGPase small subunit from a first plant and a C-terminus sequence from a C-terminus region of a plant AGPase small subunit from a second plant, and said chimeric plant AGPase small subunit protein comprises an amino acid mutation wherein the amino acid corresponding to the threonine amino acid at position 462 of wild type maize endosperm AGPase small subunit protein is replaced by an amino acid that confers increased heat stability when said mutant AGPase small subunit is expressed to form an AGPase enzyme, wherein said fragment comprises said amino acid mutation at position 462 and wherein said fragment provides for said increased heat stability when said fragment is expressed to form an AGPase enzyme, wherein said replacement amino acid is isoleucine; or

c) the polypeptide of a) and the polypeptide of b), wherein the polypeptide of a) and polypeptide of b) form a multimeric protein complex.

11. A transformed or transgenic plant or plant tissue or cell comprising:

a) a polypeptide encoded by a polynucleotide encoding a mutant plant AGPase small subunit protein, or a functional fragment of said protein, said protein comprising an amino acid mutation wherein the amino acid corresponding to the threonine amino acid at position 462 of wild type maize endosperm AGPase small subunit protein is replaced by an amino acid that confers increased heat stability when said mutant AGPase small subunit is expressed to form an AGPase enzyme, wherein said fragment comprises said amino acid mutation at position 462 and wherein said fragment provides for said increased heat stability when said fragment is expressed to form an AGPase enzyme, wherein said replacement amino acid is isoleucine; or

b) a polypeptide encoded by a polynucleotide encoding a chimeric plant AGPase small subunit protein, or a functional fragment of said protein, wherein said chimeric AGPase protein comprises an N-terminus sequence from an N-terminus region of a plant AGPase small subunit from a first plant and a C-terminus sequence from a C-terminus region of a plant AGPase small subunit from a second plant, and said chimeric plant AGPase small subunit protein comprises an amino acid mutation wherein the amino acid corresponding to the threonine amino acid at position 462 of wild type maize endosperm AGPase small subunit protein is replaced by an amino acid that confers increased heat stability when said mutant AGPase small subunit is expressed to form an AGPase enzyme, wherein said fragment comprises said amino acid mutation at position 462 and wherein said fragment provides for said increased heat stability when said fragment is expressed to form an AGPase enzyme, wherein said replacement amino acid is isoleucine; or

c) the polypeptide of a) and the polypeptide of b), wherein the polypeptide of a) and polypeptide of b) form a multimeric protein complex.

12. The plant or plant tissue or cell according to claim 11 , wherein said plant or plant tissue or cell is monocotyledonous.

13. The plant or plant tissue or cell according to claim 12 , wherein said monocotyledonous plant or plant tissue or cell is selected from the group consisting of rice, wheat, barley, oats, rye, sorghum, maize, sugarcane, pineapple, onion, bananas, coconut, lilies, turfgrasses, and millet.

14. A method of increasing resistance of a plant to heat stress conditions and/or increasing starch biosynthesis of a plant, said method comprising incorporating one or more polynucleotide into the genome of a plant and expressing the protein encoded by said polynucleotide, wherein said polynucleotide is or comprises:

a) any polynucleotide encoding a mutant plant AGPase small subunit protein, or a functional fragment of said protein, said protein comprising an amino acid mutation wherein the amino acid corresponding to the threonine amino acid at position 462 of wild type maize endosperm AGPase small subunit protein is replaced by an amino acid that confers increased heat stability when said mutant AGPase small subunit is expressed to form an AGPase enzyme, wherein said fragment comprises said amino acid mutation at position 462 and wherein said fragment provides for said increased heat stability when said fragment is expressed to form an AGPase enzyme, wherein said replacement amino acid is isoleucine; and/or

b) any polynucleotide encoding a chimeric plant AGPase small subunit protein, or a functional fragment of said protein, wherein said chimeric AGPase protein comprises an N-terminus sequence from an N-terminus region of a plant AGPase small subunit from a first plant and a C-terminus sequence from a C-terminus region of a plant AGPase small subunit from a second plant, and said chimeric plant AGPase small subunit protein comprises an amino acid mutation wherein the amino acid corresponding to the threonine amino acid at position 462 of wild type maize endosperm AGPase small subunit protein is replaced by an amino acid that confers increased heat stability when said mutant AGPase small subunit is expressed to form an AGPase enzyme, wherein said fragment comprises said amino acid mutation at position 462 and wherein said fragment provides for said increased heat stability when said fragment is expressed to form an AGPase enzyme, wherein said replacement amino acid is isoleucine.

15. The method according to claim 14 , wherein said plant is monocotyledonous.

16. The method according to claim 15 , wherein said monocotyledonous plant is selected from the group consisting of rice, wheat, barley, oats, rye, sorghum, maize, sugarcane, pineapple, onion, bananas, coconut, lilies, turfgrasses, and millet.

17. A method for preparing a plant having a mutant AGPase enzyme that provides for increased heat stability and/or increased starch biosynthesis in the plant relative to a plant expressing a wild type AGPase enzyme, said method comprising introducing one or more polynucleotide into a plant cell and growing a plant from said plant cell, wherein said plant expresses said mutant AGPase enzyme, wherein said polynucleotide is or comprises:

a) any polynucleotide encoding a mutant plant AGPase small subunit protein, or a functional fragment of said protein, said protein comprising an amino acid mutation wherein the amino acid corresponding to the threonine amino acid at position 462 of wild type maize endosperm AGPase small subunit protein is replaced by an amino acid that confers increased heat stability when said mutant AGPase small subunit is expressed to form an AGPase enzyme, wherein said fragment comprises said amino acid mutation at position 462 and wherein said fragment provides for said increased heat stability when said fragment is expressed to form an AGPase enzyme, wherein said replacement amino acid is isoleucine; and/or

b) any polynucleotide encoding a chimeric plant AGPase small subunit protein, or a functional fragment of said protein, wherein said chimeric AGPase protein comprises an N-terminus sequence from an N-terminus region of a plant AGPase small subunit from a first plant and a C-terminus sequence from a C-terminus region of a plant AGPase small subunit from a second plant, and said chimeric plant AGPase small subunit protein comprises an amino acid mutation wherein the amino acid corresponding to the threonine amino acid at position 462 of wild type maize endosperm AGPase small subunit protein is replaced by an amino acid that confers increased heat stability when said mutant AGPase small subunit is expressed to form an AGPase enzyme, wherein said fragment comprises said amino acid mutation at position 462 and wherein said fragment provides for said increased heat stability when said fragment is expressed to form an AGPase enzyme, wherein said replacement amino acid is isoleucine.

18. The method according to claim 17 , wherein said plant is monocotyledonous.

19. The method according to claim 18 , wherein said monocotyledonous plant is selected from the group consisting of rice, wheat, barley, oats, rye, sorghum, maize, sugarcane, pineapple, onion, bananas, coconut, lilies, turfgrasses, and millet.