Masao Konoshima

Pigment formation in callus cultures of Lithospermum erythrorhizon

Abstract Undifferentiated callus tissues of Lithospermum erythrorhizon are capable of synthesizing shikonin derivatives, which are normally formed in the cork cells of the roots. Their biosynthesis in cultured cells is controlled by auxin and light. The pigment content increased linearly with time after a lag phase when callus tissues were grown on culture medium containing IAA in the dark, whereas it markedly decreased when 2,4-D was substituted for IAA or when cultures were irradiated with blue light.

Effect of nutritional factors on shikonin derivative formation in Lithospermum callus cultures

Abstract Some nutritional factors affecting the biosynthesis of shikonin derivatives in callus cultures of Lithospermum erythrorhizon were examined. High sucrose concentrations increased the content of shikonin derivatives, but neither glucose nor fructose was effective for shikonin derivative formation. High concentrations of nitrogen sources inhibited or retarded shikonin derivative formation and streptomycin sulphate stimulated their biosynthesis. Addition of ascorbic acid increased the content of shikonin derivatives. Among some precursors tested only l -phenylalanine had a positive effect. At high concentrations, Ca 2+ and Fe 2+ inhibited the biosynthesis of shikonin derivatives.

Variation in pigment production in Lithospermum erythrorhizon callus cultures

Abstract Different strains of callus cultures of Lithospermum erythrorhizon showed wide variations in the production of shikonin derivatives. From these cultures, two high pigment-producing strains, whose content of shikonin derivatives are stable and similar to that of intact plant root, have been established by repeated selection.

Organization and alkaloid production in tissue cultures of scopolia parviflora

Abstract Callus cultures have been established from stem and rhizome segments of Scopolia parviflora , a tropane alkaloid-producing plant. These cultures initiate organs, especially large numbers of roots in spite of the presence of auxin in the culture medium. This root-forming capacity of the callus tissues has been maintained through serial subcultures for more than 2 years. The alkaloid content of the cultures grown on the basal medium is much less than that of the intact rhizome, although it can be increased to 0·12% by a sufficient supply of tropic acid, the precursor of the acidic moiety of the ester alkaloids hyoscyamine and scopolamine. In contrast to the unorganized tissues, the roots initiated from callus cultures tend to produce the normal pattern of alkaloids, suggesting the operation of self-regulation for alkaloid synthesis as part of the organization. Alkaloid content can be increased to 0·08% by the transfer of root-initiated tissues to an appropriate liquid medium for the development of roots in suspension culture.

Regulation of nicotine production in tobacco tissue culture by plant growth regulators

Abstract Effects of plant growth regulators on nicotine production in the callus tissues derived from the stem of Nicotiana tabacum L. var. “Bright Yellow” were examined. Experiments clearly demonstrated that kinetin promotes nicotine production in the absence of auxin (IAA or 2,4-D) in the culture medium, whereas auxin strongly inhibits nicotine formation even in the presence of kinetin, without affecting tissue growth. When cultures were grown on an auxin-free medium containing kinetin, the amount of nicotine increased strikingly after a lag phase. It was shown further that 2,4-D brings about marked changes in the composition of free amino acids in the cultured tissues, particularly regarding the quantities of glutamic and aspartic acids known as initial precursors of nicotine.

Glucosylation of phenolic compounds by Datura innoxia suspension cultures

Abstract Datura innoxia grown in suspension cultures can glucosylate simple phenols. Three isomers of dihydroxybenzene (hydroquinone, resorcinol and catechol) were readily converted into their corresponding mono-β-glucosides. Both salicyl alcohol and salicylaldehyde fed to the cells were transformed specifically to isosalicin instead of salicin. Furthermore, the analysis of the cells treated with salicylic acid suggested the formation of its glucose ester in addition to the corresponding monoglucoside. Feeding experiments showed that the cultured cells possess a remarkably high capacity for glucosylation of hydroquinone, which was totally converted into arbutin within 10 hr after administration. The in vitro glucosylation of hydroquinone carried out by the cell-free extract demonstrated that this enzymic reaction requires the presence of UDPG as a high energy donor of glucose.

Formation of acetyltropine in Datura callus cultures

Abstract The production of tropoylesters in suspension cultures of Datura innoxia stem callus was significantly stimulated by dl -tropic acid, phenylpyruvate or tropine, but was little affected by l -phenylalanine or l -ornithine. Analyses have shown that acetyltropine is synthesized in large quantities by cultured cells when tropine has been supplied to various cultures of D. innoxia and D. tatula . Acetyltropine has been isolated from either the culture medium or cells supplied with tropine. These results indicate that tropine absorbed by the cultured cells of Datura is esterified predominantly by acetic acid to form acetyltropine, instead of other tropane alkaloids.