The Influence of Light on Synthesis of Protein and of Chlorogenic Acid in Potato Tuber Tissue

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Abstract
Light stimulates the synthesis both of chlorogenic acid and of proteins in disks of pulp tissue from potato tubers. A brief exposure of disks to light of relatively low intensity doubles the accumulation of chlorogenic acid and is required for net synthesis of proteins by disks subsequently placed in the dark for 24 hours. The rate of chlorogenic acid synthesis in disks cultured in the light in- creases continuously for at least 40 hours, attaining very high levels. Continuous illumination also stimulates protein synthesis greatly and leads to greening and to chloroplast development in the disks. Chloro-genic acid synthesis is inhibited by high concentrations of ethionine and chloramphenicol. Ethionine inhibition is reversed by methionine. Protein synthesis is also decreased by ethionine, but the inhibitor does not interfere with the conversion of phenylalanine to chlorogenic acid. Formation of new proteins appears to be required for maximal rates of phenolic synthesis in tuber disks. Light is thought to stimulate chlorogenic acid formation by virtue of its effect on protein synthesis. The response of tuber slices to light is similar to that of etiolated tissue. Consequently, the effects of illumination on chlorogenic acid and protein synthesis may result from a light-induced development of chloroplasts in the slices.