Biosynthetic studies of hyoscyamine in callus tissue and intact plants of Atropa Belladonna L.



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The biosynthetic pathway of the tropane alkaloids in Atropa belladonna L. was investigated in root callus as well as in the intact plant. The callus was grown in normal media, in test media depleted of growth factors, and in test media enriched with precursors. The growth rate and alkaloid content of calli grown in these different media were compared. It was found that phenyl pyruvate produced a significant increase in alkaloid production while the increase due to phenylalanine was very slight, indicating an impairment in the conversion of phenylalanine to tropic acid. Cinnamic acid, in addition to inhibiting the growth, caused a reduction in the alkaloid content, suggesting that phenylalanine more likely undergoes transamination rather than deamination. Tyrosine also did not stimulate alkaloid production in root callus. In tagged precursor studies using leaf discs; however, tyrosine showed a lower percentage of incorporation than did phenylalanine. This might imply an indirect biosynthetic route rather than a direct incorporation from an exogenous amino acid pool. Leaf discs of Atropa belladonna L. are capable of synthesizing alkaloids; therefore, roots are not the only site for tropane alkaloid production as suggested by other workers. When plants were deprived of light and nutrients over a 13 day period, the alkaloid content slowly decreased, suggesting that the alkaloids were being converted to other substances.