Effects of low-dose gamma-irradiation on production of shikonin derivatives in callus cultures of <i>Lithospermum erythrorhizon</i> S.

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P><P>The yield increase of secondary metabolite production was examined in plant cell cultures with the use of relatively low to high doses gamma irradiation. Suspension culture of <I>Lithospermum erythrorhizon</I> cells was irradiated to 2, 16, and 32Gy. The gamma irradiation significantly stimulated the shikonin biosynthesis of the cells and increased the total shikonin yields (intracellular+extracellular shikonin yields) by 400% at 16Gy and by only 240% and 180% at 2 and 32Gy, respectively. One of the key enzymes for the shikonin biosynthesis of cells, <I>p</I>-hydroxylbenzoic acid (PHB) geranyltransferase, was found to be stimulated by the gamma-radiation treatments. The activity of PHB geranyltransferase was increased at 2 and 16Gy with a negligible change at 32Gy. In contrast, the activity of PHB glucosyltransferase was slightly changed at all doses of gamma radiation compared with the control cells. Therefore, the increase in PHB geranyltransferase activity leads to the accumulation of secondary metabolites such as a shikonin, which may contribute to plant defense against the stresses induced by gamma irradiation.</P>