Externally added Coniferyl alcohol at high concentrations reduces the growth of Nicotiana cells and seedlings. Coniferyl alcohol is metabolized by BY-2 cells to several compounds. Coniferyl alcohol (CA) is a common monolignol and a building block of lignin. The toxicity of monolignol alcohols has been stated in the literature, but there are only few studies suggesting that this is true.
METHODS AND RESULTS:
We investigated the physiological effects of Coniferyl alcohol on living plant cells in more detail. Tobacco (Nicotiana tabacum) Bright yellow-2 cells (BY-2) and Nicotiana benthamiana seedlings both showed concentration-dependent growth retardation in response to 0.5-5 mM Coniferyl alcohol treatment. In some cases, Coniferyl alcohol addition caused cell death in BY-2 cultures, but this response was dependent on the growth stage of the cells. Based on LC-MS/MS analysis, BY-2 cells did not accumulate the externally supplemented Coniferyl alcohol, but metabolized it to ferulic acid, ferulic acid glycoside, coniferin, and to some other phenolic compounds. In addition to growth inhibition, Coniferyl alcohol caused the formation of a lignin-like compound detected by phloroglucinol staining in N. benthamiana roots and occasionally in BY-2 cells. To prevent this, we added potassium iodide (KI, at 5 mM) to overcome the peroxidase-mediated Coniferyl alcohol polymerization to lignin. KI had, however, toxic effects on its own: in N. benthamiana seedlings, it caused reduction in growth; in BY-2 cells, reduction in growth and cell viability. Surprisingly, Coniferyl alcohol restored the growth of KI-treated BY-2 cells and N. benthamiana seedlings.
CONCLUSIONS:
Our results suggest that Coniferyl alcohol at high concentrations is toxic to plant cells. |
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