Mutation of a bHLH transcription factor allowed almond domestication

Science. 2019 Jun 14;364(6445):1095-1098. doi: 10.1126/science.aav8197.


Wild almond species accumulate the bitter and toxic cyanogenic diglucoside amygdalin. Almond domestication was enabled by the selection of genotypes harboring sweet kernels. We report the completion of the almond reference genome. Map-based cloning using an F1 population segregating for kernel taste led to the identification of a 46-kilobase gene cluster encoding five basic helix-loop-helix transcription factors, bHLH1 to bHLH5. Functional characterization demonstrated that bHLH2 controls transcription of the P450 monooxygenase-encoding genes PdCYP79D16 and PdCYP71AN24, which are involved in the amygdalin biosynthetic pathway. A nonsynonymous point mutation (Leu to Phe) in the dimerization domain of bHLH2 prevents transcription of the two cytochrome P450 genes, resulting in the sweet kernel trait.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Substitution
  • Amygdalin / biosynthesis
  • Amygdalin / genetics*
  • Amygdalin / metabolism
  • Basic Helix-Loop-Helix Transcription Factors / chemistry
  • Basic Helix-Loop-Helix Transcription Factors / genetics*
  • Cytochrome P-450 Enzyme System / genetics
  • Domestication*
  • Gene Expression Regulation, Plant*
  • Leucine / genetics
  • Multigene Family
  • Phenylalanine / genetics
  • Plant Proteins / genetics*
  • Point Mutation
  • Protein Conformation
  • Protein Multimerization / genetics
  • Prunus dulcis / genetics*
  • Prunus dulcis / metabolism
  • Taste
  • Transcription, Genetic


  • Basic Helix-Loop-Helix Transcription Factors
  • Plant Proteins
  • Amygdalin
  • Phenylalanine
  • Cytochrome P-450 Enzyme System
  • Leucine