We claim:
1. A modified nucleic acid molecule encoding a mutant Cry1Ac protein, wherein the nucleic
acid molecule comprises a nucleotide sequence set forth in SEQ ID NO: 2, wherein the
nucleotides XXX at positions 1804-1806 of SEQ ID NO: 2 is AAA, CGT AAG, CGC,
5 CGA, CGG, AGA or AGG.
2. The modified nucleic acid molecule as claimed in claim 1, wherein the nucleic acid
molecule comprises a nucleotide sequence selected from SEQ ID Nos: 3-10.
3. An expression cassette comprising the modified nucleic acid molecule as claimed in claim
1 or 2 operably linked to a promoter.
10 4. A vector comprising the modified nucleic acid molecule as claimed in claim 1or 2 or the
expression cassette as claimed in claim 3.
5. The vector as claimed in claim 4, wherein the vector is a plasmid vector or a viral vector.
6. A mutant Cry1Ac protein encoded by the nucleic acid molecule as claimed in claim 1 or 2,
the expression cassette as claimed in claim 3, or the vector as claimed in claim 4 or 5.
15 7. The mutant Cry1Ac protein as claimed in claim 6, wherein the mutant Cry1Ac protein
comprises an amino acid sequence selected from SEQ ID NOs. 13-16.
8. The mutant Cry1Ac protein as claimed in claim 6 or 7, wherein the mutant Cry1Ac protein
shows enhanced mortality against a pest, pest larvae, pest neonates, or any combination
thereof compared to wild-type Cry1Ac protein.
20 9. The mutant Cry1Ac protein as claimed in any one of claims 6-8, wherein the mutant
Cry1Ac protein shows enhanced mortality against pink ball worm.
10. A host cell comprising the nucleic acid molecule as claimed in claim 1 or 2, the expression
cassette as claimed in claim 3, or the vector as claimed in claim 4 or 5.
11. The host cell as claimed in claim 10, wherein the host cell is a microorganism.
25 12. The host cell as claimed in claim 10, wherein the host cell is a bacterium or a plant cell.
13. The expression cassette as claimed in claim 3, the vector as claimed in claim 4 or 5, or the
host cell as claimed in any one of claims 10-12, wherein the promoter is selected from
pathogen-inducible, constitutive, tissue-preferred, wound-inducible, or chemical-regulated
promoters.
30 14. A method of enhancing resistance to a pest infection of a cotton plant, comprising
transforming at least one cotton plant cell with the modified nucleic acid molecule as
43
claimed in claim 1 or 2, the expression cassette as claimed in claim 3, or the vector as
claimed in claim 4 or 5, wherein the infection is caused by Pectinophora, Helicoverpa, or
Spodoptera.
15. The method as claimed in claim 14, wherein the modified nucleic acid molecule encodes a
5 mutant Cry1Ac protein comprising an amino acid sequence selected from SEQ ID NOs.
13-16.
16. The method as claimed in 14 or 15, wherein the cotton plant transformed with the modified
nucleic acid molecule shows 15-99% mortality against the pest, pest larvae, and/or pest
neonates compared to a plant not comprising said modified nucleic acid molecule.
10 17. A method of treating a pest infection in a cotton plant, comprising applying the mutant
Cry1Ac protein as claimed in any one of claims 6-9 to the cotton plant or a part thereof,
wherein the infection is caused by Pectinophora, Helicoverpa, or Spodoptera.
18. The method as claimed in claim 17, wherein the part thereof is root, leaves, stem, seed, or any combination thereof.