Conversion of tryptophan to indole-3-acetic acid by TRYPTOPHAN AMINOTRANSFERASES OF ARABIDOPSIS and YUCCAs in Arabidopsis
Conversion of tryptophan to indole-3-acetic acid by TRYPTOPHAN AMINOTRANSFERASES OF ARABIDOPSIS and YUCCAs in Arabidopsis
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DOI：
10.1073/pnas.1108436108
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发表时间：
2011-11-08
影响因子：
11.1
通讯作者：
Zhao, Yunde
中科院分区：
文献类型：
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作者：
Won, Christina;Shen, Xiangling;Zhao, Yunde
生长素是一种必需激素，但其在植物中的生物合成途径尚未完全明确。在本文中，我们表明拟南芥色氨酸氨基转移酶 (TAA) 家族氨基转移酶将色氨酸转化为吲哚-3-丙酮酸 (IPA)，而黄素单加氧酶 YUCCA (YUC) 家族参与将 IPA 转化为吲哚-3-乙酸（植物中主要的生长素）。 YUC 和 TAA 均已被证明在生长素生物合成中发挥重要作用，但有人认为它们参与两个独立的途径。在这里，我们表明所有 taa 突变体表型，包括避荫缺陷、根对乙烯和 N-1-萘基邻苯二甲酸 (NPA) 的抗性，都是通过失活 YUC 基因来复制的。另一方面，我们表明，几种已知的生长素突变体背景（包括 pid 和 npy1）中的 taa 突变体模仿了 yuc 突变体与生长素突变体组合引起的所有明确的发育缺陷。此外，我们发现YUC1的过度表达部分抑制了taa1的避荫缺陷以及弱而不是强taa突变体的不育表型。此外，我们发现YUC过表达系的生长素过量产生表型依赖于活性TAA基因。我们的遗传数据表明，YUC 和 TAA 在同一途径中发挥作用，并且 YUC 是 TAA 的下游。 yuc突变体积累IPA，而taa突变体部分IPA缺陷，表明TAA负责将色氨酸转化为IPA，而YUC在将IPA转化为吲哚-3-乙酸方面发挥重要作用。
Auxin is an essential hormone, but its biosynthetic routes in plants have not been fully defined. In this paper, we show that the TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS (TAA) family of amino transferases converts tryptophan to indole-3-pyruvate (IPA) and that the YUCCA (YUC) family of flavin monooxygenases participates in converting IPA to indole-3-acetic acid, the main auxin in plants. Both the YUCs and the TAAs have been shown to play essential roles in auxin biosynthesis, but it has been suggested that they participate in two independent pathways. Here, we show that all of the taa mutant phenotypes, including defects in shade avoidance, root resistance to ethylene and N-1-naphthylphthalamic acid (NPA), are phenocopied by inactivating YUC genes. On the other hand, we show that the taa mutants in several known auxin mutant backgrounds, including pid and npy1, mimic all of the well-characterized developmental defects caused by combining yuc mutants with the auxin mutants. Furthermore, we show that overexpression of YUC1 partially suppresses the shade avoidance defects of taa1 and the sterile phenotypes of the weak but not the strong taa mutants. In addition, we discovered that the auxin overproduction phenotypes of YUC overexpression lines are dependent on active TAA genes. Our genetic data show that YUC and TAA work in the same pathway and that YUC is downstream of TAA. The yuc mutants accumulate IPA, and the taa mutants are partially IPA-deficient, indicating that TAAs are responsible for converting tryptophan to IPA, whereas YUCs play an important role in converting IPA to indole-3-acetic acid.