TY - JOUR
T1 - Arabidopsis thaliana auxotrophs reveal a tryptophan-independent biosynthetic pathway for indole-3-acetic acid
AU - Normanly, Jennifer
AU - Cohen, Jerry D.
AU - Fink, Gerald R.
PY - 1993/11/1
Y1 - 1993/11/1
N2 - We used tryptophan auxotrophs of the dicot Arabidopsis thaliana (wall cress) to determine whether tryptophan has the capacity to serve as a precursor to the auxin, indole-3-acetic acid (IAA). Quantitative gas chromatography-selected ion monitoring-mass spectrometry (GC-SIM-MS) revealed that the trp2-1 mutant, which is defective in the conversion of indole to tryptophan, accumulated amide- and ester-linked IAA at levels 38-fold and 19-fold, respectively, above those of the wild type. Tryptophan and free IAA were isolated from the trp2-1 mutant grown in the presence of [15N]anthranilate and [2H5]tryptophan, and the relative 15N and 2H5 enrichments of tryptophan and IAA were determined via GC-SIM-MS. The 15N enrichment of tryptophan, 13% ± 4%, was less than the 15N enrichment of the IAA pool, 39% ± 4%; therefore, IAA biosynthesis occurs via a tryptophan-independent pathway. The amount of 2H5 incorporated by the plant into IAA from tryptophan (9% ± 4%) was low and only slightly above the level of spontaneous, nonenzymatic conversion of [2H5]tryptophan to [2H5]IAA. These results show that the dicot Arabidopsis is similar to the monocot Zea mays in that the major route of IAA biosynthesis does not occur through tryptophan.
AB - We used tryptophan auxotrophs of the dicot Arabidopsis thaliana (wall cress) to determine whether tryptophan has the capacity to serve as a precursor to the auxin, indole-3-acetic acid (IAA). Quantitative gas chromatography-selected ion monitoring-mass spectrometry (GC-SIM-MS) revealed that the trp2-1 mutant, which is defective in the conversion of indole to tryptophan, accumulated amide- and ester-linked IAA at levels 38-fold and 19-fold, respectively, above those of the wild type. Tryptophan and free IAA were isolated from the trp2-1 mutant grown in the presence of [15N]anthranilate and [2H5]tryptophan, and the relative 15N and 2H5 enrichments of tryptophan and IAA were determined via GC-SIM-MS. The 15N enrichment of tryptophan, 13% ± 4%, was less than the 15N enrichment of the IAA pool, 39% ± 4%; therefore, IAA biosynthesis occurs via a tryptophan-independent pathway. The amount of 2H5 incorporated by the plant into IAA from tryptophan (9% ± 4%) was low and only slightly above the level of spontaneous, nonenzymatic conversion of [2H5]tryptophan to [2H5]IAA. These results show that the dicot Arabidopsis is similar to the monocot Zea mays in that the major route of IAA biosynthesis does not occur through tryptophan.
KW - Auxin
KW - Gas chromatography-selected ion monitoring-mass spectrometry
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U2 - 10.1073/pnas.90.21.10355
DO - 10.1073/pnas.90.21.10355
M3 - Article
C2 - 8234297
AN - SCOPUS:0027431896
VL - 90
SP - 10355
EP - 10359
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
SN - 0027-8424
IS - 21
ER -