Plants having increased tolerance to herbicides

An isolated nucleic acid encoding a mutated protoporphyrinogen oxidase (mut-PPO) polypeptide, wherein the encoded mut-PPO polypeptide is a variant having an amino acid sequence with at least 75% identity to SEQ ID NO:

• and comprising an amino acid substitution at a position corresponding to position Leu397 of SEQ ID NO:
• 2 and an amino acid substitution at a position corresponding to position Phe420 of SEQ ID NO:
• 2, wherein the amino acid at a position corresponding to position Leu397 of SEQ ID NO:2 is substituted with aspartate, glutamate, or glutamine, and wherein the amino acid corresponding to position Phe420 of SEQ ID NO:2 is substituted with valine or methionine.