Department of Genetics, University of California, 94720, Berkeley, CA, USA.
Planta. 1979 Jan;145(4):339-45. doi: 10.1007/BF00388358.
A 5-methyltryptophan(5-MT)-resistant cell line of wild carrot (Daucus carota L.), W001, that exhibited auxin-independent callus growth, was found to accumulate indole-3-acetic acid (IAA) and tryptophan (trp). Anthranilate-synthetase activity in W001 cell extract was less sensitive to feedback inhibition by trp than in the original 5-MT-sensitive cell lines. It is hypothesized that the resistant enzyme allowed more trp synthesis and accumulation which, in turn, affected the IAA concentration in the cell. Since carrot cultures cannot regenerate in the presence of exogenous auxin, the elevated IAA concentration in W001 may be responsible for its drastically reduced capacity to regenerate. The relationship between trp and IAA levels was further investigated by examining the effect of 2,4-dichlorophenoxy acetic acid (2,4-D) on the endogenous concentration of trp and IAA. In general, the IAA level was reduced but the trp concentration was elevated when 2,4-D was present in the culture medium.
野生胡萝卜（Daucus carota L.）的 5-甲基色氨酸（5-MT）抗性细胞系 W001 表现出对生长素不依赖的愈伤组织生长，该细胞系积累吲哚-3-乙酸（IAA）和色氨酸（trp）。W001 细胞提取物中的邻氨基苯甲酸合酶活性对 trp 的反馈抑制作用比对原始 5-MT 敏感细胞系的活性更不敏感。因此假设，抗性酶允许更多的 trp 合成和积累，进而影响细胞中的 IAA 浓度。由于胡萝卜培养物在存在外源生长素的情况下不能再生，因此 W001 中升高的 IAA 浓度可能是其再生能力大大降低的原因。通过检查 2,4-二氯苯氧乙酸（2,4-D）对内源 trp 和 IAA 浓度的影响，进一步研究了 trp 和 IAA 水平之间的关系。通常，当培养基中存在 2,4-D 时，IAA 水平降低，但 trp 浓度升高。
