Factors Affecting Phytoalexin Production in Cultured Carrot Cells

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Abstract
The production of 6-methoxymellein, a phytoalexin, in cultured carrot cells under various growth conditions was studied using two induction methods; by adding partial hydrolysates obtained by treating the cells with pectinase or trypsin, or by directly adding these enzymes to growing cells to cause the release of cellular components as endogenous elicitor. 6-Methoxymellein production depended greatly on the cell culture age. Maximal production was found in cells at the early stationary phase, while actively dividing cells had only negligible amounts. Release of elicitor from the cells by pectinase or trypsin was also influenced by the culture stage. Effective elicitor was obtained only from cells in the late logarithmic and early stationary phases. 6-Methoxymellein production required the presence of 2,4-D. IAA could not substitute for 2,4-D, though partial hydrolysates prepared from these cells grown with IAA or without auxin showed significant elicitor activity. On the other hand, the production was inhibited by actinomycin D or cycloheximide, suggesting that de novo syntheses of RNA and protein are required for the phytoalexin production.