Chalcone synthase from Camellia sinensis: isolation of the cDNAs and the organ-specific and sugar-responsive expression of the genes.

Three full-length cDNAs (CHS1, CHS2 and CHS3) encoding chalcone synthase (CHS; EC 2.3.1.74) were isolated from young leaves of Camellia sinensis. Each cDNA encoded 389 amino acid residues, which showed 93-96% identity to one another. Oligonucleotides were synthesized on the basis of the 5'-untranslated sequences of the cDNAs and their corresponding transcripts could be distinguished. The CHS1, CHS2 and CHS3 transcripts were abundant in the leaves and stems. After an initial treatment with water in darkness, the transcripts fell to very low levels in the young leaves. These levels were increased by a subsequent treatment with fructose, sucrose or maltose in darkness, and they increased still further upon a treatment with glucose, sucrose or maltose under continuous light. These results indicate that the CHS1, CHS2 and CHS3 transcripts are expressed in various organs and respond to sugars in young leaves in a similar manner. The effect of continuous light is also discussed.