2,4-D Resistance in a Tobacco Cell Culture Variant : II. Effects of 2,4-D on Nucleic Acid and Protein Synthesis and Cell Respiration

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The effects of 2,4-D on nucleic acid and protein synthesis and cell respiration were compared between a 2,4-D-resistant variant and its wild-type cell lines of tobacco (Nicotiana tabacum L.). The variant continued cell division and growth in the presence of 100 μM 2,4-D which was strongly inhibitory to the wild-type cell lines. Among the macromolecular syntheses studied, DNA synthesis was the most sensitive and protein synthesis was the least sensitive to inhibitory concentrations of 2,4-D. The variant displayed threefold higher resistance to 2,4-D than the wild-type cell line based on the 50% inhibitory concentrations of 2,4-D on DNA synthesis. No significant differences which could explain the 2,4-D resistance were found between the variant and the wild-type cell lines in 2,4-D concentrations required to inhibit RNA and protein synthesis. The effect of 2,4-D on cell respiration was detectable without a noticeable lag. The resistance of the variant based on the effect on cell respiration also was apparent immediately after 2,4-D addition. According to the 50% inhibitory concentrations of 2,4-D on cell respiration, the variant showed a level of resistance similar to that estimated by DNA synthesis. These results indicate that the resistance of the variant is due to a modification which reduces the cellular sensitivity to phyto-toxic concentrations of 2,4-D with respect to, at least, DNA synthesis and respiration.
日本植物生理学会の論文